These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Large Eddy simulation of parallel blade-vortex interaction  

NASA Astrophysics Data System (ADS)

Helicopter Blade-Vortex Interaction (BVI) generally occurs under certain conditions of powered descent or during extreme maneuvering. The vibration and acoustic problems associated with the interaction of rotor tip vortices and the following blades is a major aerodynamic concern for the helicopter community. Numerous experimental and computational studies have been done over the last two decades in order to gain a better understanding of the physical mechanisms involved in BVI. The most severe interaction, in terms of generated noise, happens when the vortex filament is parallel to the blade, thus affecting a great portion of it. The majority of the previous numerical studies of parallel BVI fall within a potential flow framework. Some Navier-Stokes approaches using dissipative numerical methods and RANS-type turbulence models have also been attempted, but with limited success. The current investigation makes use of an incompressible, non-dissipative, kinetic energy conserving collocated mesh scheme in conjunction with a dynamic subgrid-scale model. The concentrated tip vortex is not attenuated as it is convected downstream and over a NACA-0012 airfoil. The lift, drag, moment and pressure coefficients induced by the passage of the vortex are monitored in time and compared with experimental data.

Felten, Frederic; Lund, Thomas

2002-11-01

2

Measurement of parallel blade–vortex interaction at low Reynolds numbers  

Microsoft Academic Search

In this study parallel blade–vortex interaction for a Schmidt-propeller configuration has been examined using particle image\\u000a velocimetry (PIV). This tandem configuration consists of a leading airfoil (forefoil), used to generate a vortical wake of\\u000a leading-edge vortices (LEVs) and trailing-edge vortices (TEVs) through a pitching or plunging motion, and a trailing airfoil\\u000a (hindfoil), held fixed with a specified angle of attack

David Rival; Roland Manejev; Cam Tropea

2010-01-01

3

Measurement of parallel blade-vortex interaction at low Reynolds numbers  

NASA Astrophysics Data System (ADS)

In this study parallel blade-vortex interaction for a Schmidt-propeller configuration has been examined using particle image velocimetry (PIV). This tandem configuration consists of a leading airfoil (forefoil), used to generate a vortical wake of leading-edge vortices (LEVs) and trailing-edge vortices (TEVs) through a pitching or plunging motion, and a trailing airfoil (hindfoil), held fixed with a specified angle of attack and vertical spacing in its wake. The hindfoil incidence (loading) and not the vertical spacing to the incoming vortical wake has been found to dictate the nature of the interaction (inviscid vs. viscous). For cases where the vortex-blade offset is small and the hindfoil is loaded, vortex distortion and vortex-induced separations are observed. By tracking the circulation of the LEV and TEV, it has been found that the vortices are strengthened for the tandem arrangement and in certain cases dissipate quicker in the wake when interacting with the hindfoil. Time-averaged forces obtained using a standard control-volume analysis are then obtained and used to evaluate these vortex-interaction cases. A subsequent analysis of the varying pressure distribution over the suction side of the hindfoil is performed by integrating the Navier-Stokes equations through the velocity field. This allows for a direct comparison of the vortex-induced loading for the various configurations.

Rival, David; Manejev, Roland; Tropea, Cam

2010-07-01

4

Rotorcraft Blade-Vortex Interaction Controller  

NASA Technical Reports Server (NTRS)

Blade-vortex interaction noises, sometimes referred to as 'blade slap', are avoided by increasing the absolute value of inflow to the rotor system of a rotorcraft. This is accomplished by creating a drag force which causes the angle of the tip-path plane of the rotor system to become more negative or more positive.

Schmitz, Fredric H. (Inventor)

1995-01-01

5

Rotor blade–vortex interaction noise  

Microsoft Academic Search

Blade–vortex interaction noise-generated by helicopter main rotor blades is one of the most severe noise problems and is very important both in military applications and community acceptance of rotorcraft. Research over the decades has substantially improved physical understanding of noise-generating mechanisms, and various design concepts have been investigated to control noise radiation using advanced blade planform shapes and active blade

Young H. Yu

2000-01-01

6

Blade-vortex interaction experiments - Velocity and vorticity fields  

NASA Technical Reports Server (NTRS)

The blade-vortex interaction problem is studied experimentally with laser-Doppler velocimetry. Vortices are generated by pitching a NACA 0012 airfoil about its quarter chord and a target airfoil is mounted two chord lengths downstream of the vortex generator. LDV measurements are obtained in the neighborhood of the target airfoil's leading edge and ensemble-averaged velocity vector fields and vorticity contours are constructed. Vorticity fields are also constructed from velocity time records by assuming that, over short distances, the vorticity propagates with the local velocity. This assumption allows the blade-vortex interaction to be simulated from very few measurements.

Wilder, Michael C.; Pesce, Matthew M.; Telionis, Demetri P.; Poling, David R.

1990-01-01

7

An experimental investigation of blade-vortex interaction at normal incidence  

NASA Technical Reports Server (NTRS)

An experimental investigation has been conducted for the blade-vortex interaction (BVI) of a rotor at normal incidence, where the vortex is generally parallel to the rotor axis. Tip Mach number, radial BVI station, and free stream velocity were varied during measurements of fluctuating blade pressures, far field sound pressure levels and directivity, incident vortex velocity field, and blade-vortex interaction angles. The experimental setup is representative of the chopping of helicopter main rotor tip vortices by the tail rotor. This interaction is found to generate impulsive noise which radiates primarily ahead of the blade.

Ahmadi, A. R.

1985-01-01

8

Helicopter tail rotor blade-vortex interaction noise  

Microsoft Academic Search

A study is made of helicopter tail rotor noise, particularly that due to the interactions with main rotor tip vortices. Summarized here are present analysis, the computer codes, and the results of several test cases. Amiet's unsteady thin airfoil theory is used to calculate the acoustics of blade-vortex interaction. The noise source is modelled as a force dipole resulting from

Albert R. George; S.-T. Chou

1987-01-01

9

An analysis of blade vortex interaction aerodynamics and acoustics  

NASA Technical Reports Server (NTRS)

The impulsive noise associated with helicopter flight due to Blade-Vortex Interaction, sometimes called blade slap is analyzed especially for the case of a close encounter of the blade-tip vortex with a following blade. Three parts of the phenomena are considered: the tip-vortex structure generated by the rotating blade, the unsteady pressure produced on the following blade during the interaction, and the acoustic radiation due to the unsteady pressure field. To simplify the problem, the analysis was confined to the situation where the vortex is aligned parallel to the blade span in which case the maximum acoustic pressure results. Acoustic radiation due to the interaction is analyzed in space-fixed coordinates and in the time domain with the unsteady pressure on the blade surface as the source of chordwise compact, but spanwise non-compact radiation. Maximum acoustic pressure is related to the vortex core size and Reynolds number which are in turn functions of the blade-tip aerodynamic parameters. Finally noise reduction and performance are considered.

Lee, D. J.

1985-01-01

10

Blade vortex interaction noise reduction techniques for a rotorcraft  

NASA Technical Reports Server (NTRS)

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved).

Charles, Bruce D. (Inventor); Hassan, Ahmed A. (Inventor); Tadghighi, Hormoz (Inventor); JanakiRam, Ram D. (Inventor); Sankar, Lakshmi N. (Inventor)

1998-01-01

11

Blade vortex interaction noise reduction techniques for a rotorcraft  

NASA Technical Reports Server (NTRS)

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved).

Charles, Bruce D. (Inventor); Hassan, Ahmed A. (Inventor); Tadghighi, Hormoz (Inventor); JanakiRam, Ram D. (Inventor); Sankar, Lakshmi N. (Inventor)

1996-01-01

12

Rotating hot-wire investigation of the vortex responsible for blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

This distribution of the circumferential velocity of the vortex responsible for blade-vortex interaction noise was measured using a rotating hot-wire rake synchronously meshed with a model helicopter rotor at the blade passage frequency. Simultaneous far-field acoustic data and blade differential pressure measurements were obtained. Results show that the shape of the measured far-field acoustic blade-vortex interaction signature depends on the blade-vortex interaction geometry. The experimental results are compared with the Widnall-Wolf model for blade-vortex interaction noise.

Fontana, Richard Remo

1988-01-01

13

Helicopter tail rotor orthogonal blade vortex interaction  

Microsoft Academic Search

The aerodynamic operating environment of the helicopter is particularly complex and, to some extent, dominated by the vortices trailed from the main and tail rotors. These vortices not only determine the form of the induced flow field but also interact with each other and with elements of the physical structure of the flight vehicle. Such interactions can have implications in

F. N. Coton; J. S. Marshall; R. A. Mc D. Galbraith; R. B. Green

2004-01-01

14

Flow visualizations of perpendicular blade vortex interactions  

NASA Technical Reports Server (NTRS)

Helium bubble flow visualizations have been performed to study perpendicular interaction of a turbulent trailing vortex and a rectangular wing in the Virginia Tech Stability Tunnel. Many combinations of vortex strength, vortex-blade separation (Z(sub s)) and blade angle of attack were studied. Photographs of representative cases are presented. A range of phenomena were observed. For Z(sub s) greater than a few percent chord the vortex is deflected as it passes the blade under the influence of the local streamline curvature and its image in the blade. Initially the interaction appears to have no influence on the core. Downstream, however, the vortex core begins to diffuse and grow, presumably as a consequence of its interaction with the blade wake. The magnitude of these effects increases with reduction in Z(sub s). For Z(sub s) near zero the form of the interaction changes and becomes dependent on the vortex strength. For lower strengths the vortex appears to split into two filaments on the leading edge of the blade, one passing on the pressure and one passing on the suction side. At higher strengths the vortex bursts in the vicinity of the leading edge. In either case the core of its remnants then rapidly diffuse with distance downstream. Increase in Reynolds number did not qualitatively affect the flow apart from decreasing the amplitude of the small low-frequency wandering motions of the vortex. Changes in wing tip geometry and boundary layer trip had very little effect.

Rife, Michael C.; Davenport, William J.

1992-01-01

15

Reduction of helicopter blade-vortex interaction noise by active rotor control technology  

Microsoft Academic Search

Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently

Yung H. Yu; Bernd Gmelin; Wolf Splettstoesser; Jean J. Philippe; Jean Prieur; Thomas F. Brooks

1997-01-01

16

A Novel Method for Reducing Rotor Blade-Vortex Interaction  

NASA Technical Reports Server (NTRS)

One of the major hindrances to expansion of the rotorcraft market is the high-amplitude noise they produce, especially during low-speed descent, where blade-vortex interactions frequently occur. In an attempt to reduce the noise levels caused by blade-vortex interactions, the flip-tip rotor blade concept was devised. The flip-tip rotor increases the miss distance between the shed vortices and the rotor blades, reducing BVI noise. The distance is increased by rotating an outboard portion of the rotor tip either up or down depending on the flight condition. The proposed plan for the grant consisted of a computational simulation of the rotor aerodynamics and its wake geometry to determine the effectiveness of the concept, coupled with a series of wind tunnel experiments exploring the value of the device and validating the computer model. The computational model did in fact show that the miss distance could be increased, giving a measure of the effectiveness of the flip-tip rotor. However, the wind experiments were not able to be conducted. Increased outside demand for the 7'x lO' wind tunnel at NASA Ames and low priority at Ames for this project forced numerous postponements of the tests, eventually pushing the tests beyond the life of the grant. A design for the rotor blades to be tested in the wind tunnel was completed and an analysis of the strength of the model blades based on predicted loads, including dynamic forces, was done.

Glinka, A. T.

2000-01-01

17

Helicopter tail rotor blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

A study is made of helicopter tail rotor noise, particularly that due to the interactions with main rotor tip vortices. Summarized here are present analysis, the computer codes, and the results of several test cases. Amiet's unsteady thin airfoil theory is used to calculate the acoustics of blade-vortex interaction. The noise source is modelled as a force dipole resulting from an airfoil of infinite span chopping through a skewed line vortex. To analyze the interactions between helicopter tail rotor and main rotor tip vortices, we developed a two-step approach: (1) the main rotor tip vortex system is obtained through a free wake geometry calculation of the main rotor using CAMRAD code; (2) acoustic analysis takes the results from the aerodynamic interaction analysis and calculates the farfield pressure signatures for the interactions. It is found that under a wide range of helicopter flight conditions, acoustic pressure fluctuations of significant magnitude can be generated by tail rotors due to a series of interactions with main rotor tip vortices. This noise mechanism depends strongly on the helicopter flight conditions and the relative location and phasing of the main and tail rotors. fluctuations of significant magnitude can be generated by tail rotors due to a series of interactions with main rotor tip vortices. This noise mechanism depends strongly upon the helicopter flight conditions and the relative location and phasing of the main and tail rotors.

George, Albert R.; Chou, S.-T.

1987-01-01

18

Flow field and acoustics of two-dimensional transonic blade-vortex interactions  

Microsoft Academic Search

Blade-vortex interaction noise from full-scale helicopters is shown to involve unsteady transonic flow phenomena which can be modeled as two-dimensional. An unsteady, small-disturbance-theory, numerical analysis, is used to model the interaction of an airfoil with a finite-core, locally-convected vortex using the vortex-in-cell method with multiple branch cuts accounting for the distributed vortices' potential jumps. Strong disturbances propagating from the blade-vortex

A. R. George; S.-B. Chang

1984-01-01

19

HART-II: Prediction of Blade-Vortex Interaction Loading  

NASA Technical Reports Server (NTRS)

During the HART-I data analysis, the need for comprehensive wake data was found including vortex creation and aging, and its re-development after blade-vortex interaction. In October 2001, US Army AFDD, NASA Langley, German DLR, French ONERA and Dutch DNW performed the HART-II test as an international joint effort. The main objective was to focus on rotor wake measurement using a PIV technique along with the comprehensive data of blade deflections, airloads, and acoustics. Three prediction teams made preliminary correlation efforts with HART-II data: a joint US team of US Army AFDD and NASA Langley, German DLR, and French ONERA. The predicted results showed significant improvements over the HART-I predicted results, computed about several years ago, which indicated that there has been better understanding of complicated wake modeling in the comprehensive rotorcraft analysis. All three teams demonstrated satisfactory prediction capabilities, in general, though there were slight deviations of prediction accuracies for various disciplines.

Lim, Joon W.; Tung, Chee; Yu, Yung H.; Burley, Casey L.; Brooks, Thomas; Boyd, Doug; vanderWall, Berend; Schneider, Oliver; Richard, Hugues; Raffel, Markus

2003-01-01

20

Helicopter model scale results of blade-vortex interaction impulsive noise as affected by blade planform  

NASA Astrophysics Data System (ADS)

An experimental investigation of the blade-vortex interaction impulsive noise characteristics of an advanced main rotor system for the UH-1 helicopter has been conducted. Models of both the advanced main rotor system and the standard UH-1 main rotor system were tested at one-quarter scale in the Langley 4- by 7-Meter (V/STOL) Tunnel using the General Rotor Model System (GRMS). Tests were conducted over a range of descent angles which bracketed the blade-vortex interaction phenomenon at a range of simulated flight speeds. The tunnel was operated in the open-throat configuration with acoustic treatment to improve the acoustic characteristics of the test chamber. The model data indicated that the advanced rotor system has increased the flight-scaled, LA noise produced by the UH-1 at all descent angles except where the blade-vortex interaction phenomenon was most intense for the standard UH-1 main rotor system.

Conner, D. A.; Hoad, D. R.

21

Helicopter blade-vortex interaction locations: Scale-model acoustics and free-wake analysis results  

NASA Technical Reports Server (NTRS)

The results of a model rotor acoustic test in the Langley 4by 7-Meter Tunnel are used to evaluate a free-wake analytical technique. An acoustic triangulation technique is used to locate the position in the rotor disk where the blade-vortex interaction noise originates. These locations, along with results of the rotor free-wake analysis, are used to define the geometry of the blade-vortex interaction noise phenomena as well as to determine if the free-wake analysis is a capable diagnostic tool. Data from tests of two teetering rotor systems are used in these analyses.

Hoad, Danny R.

1987-01-01

22

Helicopter Blade-Vortex Interaction Noise with Comparisons to CFD Calculations  

NASA Technical Reports Server (NTRS)

A comparison of experimental acoustics data and computational predictions was performed for a helicopter rotor blade interacting with a parallel vortex. The experiment was designed to examine the aerodynamics and acoustics of parallel Blade-Vortex Interaction (BVI) and was performed in the Ames Research Center (ARC) 80- by 120-Foot Subsonic Wind Tunnel. An independently generated vortex interacted with a small-scale, nonlifting helicopter rotor at the 180 deg azimuth angle to create the interaction in a controlled environment. Computational Fluid Dynamics (CFD) was used to calculate near-field pressure time histories. The CFD code, called Transonic Unsteady Rotor Navier-Stokes (TURNS), was used to make comparisons with the acoustic pressure measurement at two microphone locations and several test conditions. The test conditions examined included hover tip Mach numbers of 0.6 and 0.7, advance ratio of 0.2, positive and negative vortex rotation, and the vortex passing above and below the rotor blade by 0.25 rotor chords. The results show that the CFD qualitatively predicts the acoustic characteristics very well, but quantitatively overpredicts the peak-to-peak sound pressure level by 15 percent in most cases. There also exists a discrepancy in the phasing (about 4 deg) of the BVI event in some cases. Additional calculations were performed to examine the effects of vortex strength, thickness, time accuracy, and directionality. This study validates the TURNS code for prediction of near-field acoustic pressures of controlled parallel BVI.

McCluer, Megan S.

1996-01-01

23

Tip-path-plane angle effects on rotor blade-vortex interaction noise levels and directivity  

Microsoft Academic Search

Acoustic data of a scale model BO-105 main rotor acquired in a large aeroacoustic wind tunnel are presented to investigate the parametric effects of rotor operating conditions on blade-vortex interaction (BVI) impulsive noise. Contours of a BVI noise metric are employed to quantify the effects of rotor advance ratio and tip-path-plane angle on BVI noise directivity and amplitude. Acoustic time

Casey L. Burley; Ruth M. Martin

1988-01-01

24

Helicopter model rotor-blade vortex interaction impulsive noise - Scalability and parametric variations  

Microsoft Academic Search

Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1\\/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale

D. A. Boxwell; F. H. Schmitz; W. R. Splettstoesser; K. J. Schultz

1985-01-01

25

Helicopter model scale results of blade-vortex interaction impulsive noise as affected by blade planform  

Microsoft Academic Search

An experimental investigation of the blade-vortex interaction impulsive noise characteristics of an advanced main rotor system for the UH-1 helicopter has been conducted. Models of both the advanced main rotor system and the standard UH-1 main rotor system were tested at one-quarter scale in the Langley 4- by 7-Meter (V\\/STOL) Tunnel using the General Rotor Model System (GRMS). Tests were

D. A. Conner; D. R. Hoad

1982-01-01

26

A mechanism for mitigation of blade-vortex interaction using leading edge blowing flow control  

NASA Astrophysics Data System (ADS)

The interaction of a vortical unsteady flow with structures is often encountered in engineering applications. Such flow structure interactions (FSI) can be responsible for generating significant loads and can have many detrimental structural and acoustic side effects, such as structural fatigue, radiated noise and even catastrophic results. Amongst the different types of FSI, the parallel blade-vortex interaction (BVI) is the most common, often encountered in helicopters and propulsors. In this work, we report on the implementation of leading edge blowing (LEB) active flow control for successfully minimizing the parallel BVI. Our results show reduction of the airfoil vibrations up to 38% based on the root-mean-square of the vibration velocity amplitude. This technique is based on displacing an incident vortex using a jet issued from the leading edge of a sharp airfoil effectively increasing the stand-off distance of the vortex from the body. The effectiveness of the method was experimentally analyzed using time-resolved digital particle image velocimetry (TRDPIV) recorded at an 800 Hz rate, which is sufficient to resolve the spatio-temporal dynamics of the flow field and it was combined with simultaneous accelerometer measurements of the airfoil, which was free to oscillate in a direction perpendicular to the freestream. Analysis of the flow field spectra and a Proper Orthogonal Decomposition (POD) of the TRDPIV data of the temporally resolved planar flow fields indicate that the LEB effectively modified the flow field surrounding the airfoil and increased the convecting vortices stand-off distance for over half of the airfoil chord length. It is shown that LEB also causes a redistribution of the flow field spectral energy over a larger range of frequencies.

Weiland, Chris; Vlachos, Pavlos P.

2009-09-01

27

Experimental blade vortex interaction noise characteristics of a utility helicopter at 1/4 scale  

NASA Astrophysics Data System (ADS)

Models of both the advanced main rotor system and the standard or "baseline" UH-1 main rotor system were tested at one-quarter scale in the Langley 4- by 7-Meter (V/STOL) Tunnel using the general rotor model system. Tests were conducted over a range of descent angles which bracketed the blade-vortex interaction phenomenon for a range of simulated forward speeds. The tunnel was operated in the open-throat configuration with acoustic treatment to improve the semi-anechoic characteristics of the test chamber. Acoustical data obtained for these two rotor systems operating at similar flight conditions are presented without analysis or discussion.

Conner, D. A.; Hoad, D. R.

1984-01-01

28

An Euler code calculation of blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

An Euler code has been developed for calculation of noise radiation due to the interaction of a distributed vortex with a Joukowski airfoil. THe time-dependent incompressible flow field is first determined and then integrated to yield the resulting sound production through use of the elegant low-frequency Green's function approach. This code has several interesting numerical features involved in the vortex motion and in continuous satisfaction of the Kutta condition. In addition, it removes the limitations on Reynolds number and is much more efficient than an earlier Navier-Stokes code. Results indicate that the noise production is due to the deceleration and subsequent acceleration of the vortex as it approaches and passes the airfoil. Predicted acoustic levels and frequencies agree with measured data although a precise comparison would require the strength, size, and position of the incoming vortex to be known.

Hardin, J. C.; Lamkin, S. L.

1987-01-01

29

An Anechoic Wind Tunnel for the Investigation of the Main-Rotor\\/Tail Rotor Blade Vortex Interaction  

Microsoft Academic Search

ABSTRACT The interaction of a helicopter’s main rotor tip vortex with the tail rotor is an important source of noise and vibration, yet it is still poorly understood. An important limiting case is the orthogonal blade vortex interaction (OBVI) where a three-dimensional vortex structure is cut by the tail rotor blade. It has been discovered that the blade unsteady surface

Con J. Doolan; Damien Leclercq

2007-01-01

30

A new look at sound generation by blade/vortex interaction  

NASA Technical Reports Server (NTRS)

As a preliminary attempt to understand the dynamics of blade/vortex interaction, the two-dimensional problem of a rectilinear vortex filament interacting with a Joukowski airfoil is analyzed in both the lifting and nonlifting cases. The vortex velocity components could be obtained analytically and integrated to determine the vortex trajectory. With this information, the aeroacoustic low-frequency Green's function approach could then be employed to calculate the sound produced during the encounter. The results indicate that the vortex path deviates considerably from simple convection due to the presence of the airfoil and that a reasonably sharp sound pulse is radiated during the interaction whose fundamental frequency is critically dependent upon whether the vortex passes above or below the airfoil. Determination of this gross parameter of the interaction is shown to be highly nonlinearly dependent upon airfoil circulation, vortex circulation, and initial position.

Hardin, J. C.; Mason, J. P.

1985-01-01

31

Studies of blade-vortex interaction noise reduction by rotor blade modification  

NASA Technical Reports Server (NTRS)

Blade-vortex interaction (BVI) noise is one of the most objectionable types of helicopter noise. This impulsive blade-slap noise can be particularly intense during low-speed landing approach and maneuvers. Over the years, a number of flight and model rotor tests have examined blade tip modification and other blade design changes to reduce this noise. Many times these tests have produced conflicting results. In the present paper, a number of these studies are reviewed in light of the current understanding of the BVI noise problem. Results from one study in particular are used to help establish the noise reduction potential and to shed light on the role of blade design. Current blade studies and some new concepts under development are also described.

Brooks, Thomas F.

1993-01-01

32

Active control of blade-vortex interactions using a neuro-fuzzy controller  

NASA Astrophysics Data System (ADS)

Rotorcraft blade-vortex interactions (BVI) result in large pressure fluctuations over rotor blades leading to increased unsteady blade loads, noise, and vibration. Previous studies have indicated that an effective method for reducing BVI is through the use of active control schemes. As a workable dynamic model of the process for controller design is difficult to develop a rule-based fuzzy controller is used in this study. As the choice of the fuzzy controller parameters for acceptable performance depend on flight condition, a neural network is trained to adaptively modify the fuzzy controller parameters as a function of flight condition. The resulting neuro-fuzzy control scheme is evaluated using a numerical simulation model of BVI in order to demonstrate the effectiveness of the proposed scheme.

Swaminathan, Ramesh; Prasad, J. V. R.; Sankar, L. N.

1996-04-01

33

Effect of leading-edge porosity on blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

The effect of the porous leading-edge of an airfoil on the blade-vortex interaction noise, which dominates far-field acoustic spectrum of the helicopter, is investigated. The thin-layer Navier-Stokes equations are solved with a high-order upwind-biased scheme and a multizonal grid system. The Baldwin-Lomax turbulence model is modified for considering transpiration on the surface. The amplitudes of the propagating acoustic wave in the near-field are calculated directly from the computation. The porosity effect on the surface is modeled. Results show leading-edge transpiration can suppress pressure fluctuations at the leading-edge during BVI, and consequently reduce the amplitude of propagating noise by 30 percent at maximum in the near-field. The effect of porosity factor on the noise level is also investigated.

Lee, Soogab

1993-01-01

34

Advancing-side directivity and retreating-side interactions of model rotor blade-vortex interaction noise  

Microsoft Academic Search

Acoustic data are presented from a 40 percent scale model of the four-bladed BO-105 helicopter main rotor, tested in a large aerodynamic wind tunnel. Rotor blade-vortex interaction (BVI) noise data in the low-speed flight range were acquired using a traversing in-flow microphone array. Acoustic results presented are used to assess the acoustic far field of BVI noise, to map the

R. M. Martin; W. R. Splettstoesser; J. W. Elliott; K.-J. Schultz

1988-01-01

35

Acoustic measurements from a rotor blade-vortex interaction noise experiment in the German-Dutch Wind Tunnel (DNW)  

Microsoft Academic Search

Acoustic data are presented from a 40 percent scale model of the 4-bladed BO-105 helicopter main rotor, measured in the large European aeroacoustic wind tunnel, the DNW. Rotor blade-vortex interaction (BVI) noise data in the low speed flight range were acquired using a traversing in-flow microphone array. The experimental apparatus, testing procedures, calibration results, and experimental objectives are fully described.

Ruth M. Martin; W. R. Splettstoesser; J. W. Elliott; K.-J. Schultz

1988-01-01

36

High-Resolution Simulations of Parallel BladeVortex Interactions  

E-print Network

contribution coming from the trailing edge. The simulations are then extended to three-dimensional moving overset meshes where the vortex generation and convection is also resolved. The numerical methodology. A high-resolution solution of the compressible Euler equations is performed on structured overset meshes

Alonso, Juan J.

37

Effects of a trailing edge flap on the aerodynamics and acoustics of rotor blade-vortex interactions  

NASA Technical Reports Server (NTRS)

The use of a trailing edge flap on a helicopter rotor has been numerically simulated to determine if such a device can mitigate the acoustics of blade vortex interactions (BVI). The numerical procedure employs CAMRAD/JA, a lifting-line helicopter rotor trim code, in conjunction with RFS2, an unsteady transonic full-potential flow solver, and WOPWOP, an acoustic model based on Farassat's formulation 1A. The codes were modified to simulate trailing edge flap effects. The CAMRAD/JA code was used to compute the far wake inflow effects and the vortex wake trajectories and strengths which are utilized by RFS2 to predict the blade surface pressure variations. These pressures were then analyzed using WOPWOP to determine the high frequency acoustic response at several fixed observer locations below the rotor disk. Comparisons were made with different flap deflection amplitudes and rates to assess flap effects on BVI. Numerical experiments were carried out using a one-seventh scale AH-1G rotor system for flight conditions simulating BVI encountered during low speed descending flight with and without flaps. Predicted blade surface pressures and acoustic sound pressure levels obtained have shown good agreement with the baseline no-flap test data obtained in the DNW wind tunnel. Numerical results indicate that the use of flaps is beneficial in reducing BVI noise.

Charles, B. D.; Tadghighi, H.; Hassan, A. A.

1992-01-01

38

Flow structure generated by perpendicular blade-vortex interaction and implications for helicopter noise prediction. Volume 1: Measurements  

NASA Technical Reports Server (NTRS)

The perpendicular interaction of a streamwise vortex with an infinite span helicopter blade was modeled experimentally in incompressible flow. Three-component velocity and turbulence measurements were made using a sub-miniature four sensor hot-wire probe. Vortex core parameters (radius, peak tangential velocity, circulation, and centerline axial velocity deficit) were determined as functions of blade-vortex separation, streamwise position, blade angle of attack, vortex strength, and vortex size. The downstream development of the flow shows that the interaction of the vortex with the blade wake is the primary cause of the changes in the core parameters. The blade sheds negative vorticity into its wake as a result of the induced angle of attack generated by the passing vortex. Instability in the vortex core due to its interaction with this negative vorticity region appears to be the catalyst for the magnification of the size and intensity of the turbulent flowfield downstream of the interaction. In general, the core radius increases while peak tangential velocity decreases with the effect being greater for smaller separations. These effects are largely independent of blade angle of attack; and if these parameters are normalized on their undisturbed values, then the effects of the vortex strength appear much weaker. Two theoretical models were developed to aid in extending the results to other flow conditions. An empirical model was developed for core parameter prediction which has some rudimentary physical basis, implying usefulness beyond a simple curve fit. An inviscid flow model was also created to estimate the vorticity shed by the interaction blade, and to predict the early stages of its incorporation into the interacting vortex.

Wittmer, Kenneth S.; Devenport, William J.

1996-01-01

39

Effects of trailing edge flap dynamic deployment on blade-vortex interactions  

E-print Network

of noise generation for a typical rotorcrall. . . . . Figure 2: Noise boundaries for dominant noise sources. Figure 3: Rotor wake structure showing interactions between blades and tip vortices. . . . . Figure 4: The two limiting cases ofblade... INTERACTION ROTOR-FUSELAGE INTERFERENCE TRANSONIC EFFECTS Figure I: Various sources of noise generation for a typical rotorcraft. This thesis follows the style of Journal of Aircraft. 1000 500 1 - SLAP BOUNDARY 2. CONTINUOUS SLAP IIEPULSIVE 3- MAXIMUM...

Nelson, Carter T.

2012-06-07

40

Blade-vortex noise on a helicopter main rotor. Study of the strong two dimensional incompressible interaction  

Microsoft Academic Search

A parametric study of the strong interactions in incompressible two dimensions is described. The study allows for the elaboration of an air vortex model compatible with the calculations of such interactions and allows the effects of various parameters of the interaction to be elucidated. Parameters such as the position of the air vortex, its intensity, the dimensions of its viscous

G. Rahier

1991-01-01

41

A reduced Blade-Vortex Interaction rotor  

E-print Network

that is the location of the microphone on the surface of the blade. It can be seen Irom the plot that the majority of the advancing side BVI events occur in the azimuthal range tlr = 0 to tlr = 60. As the advance ratio increases, the spacing between the BVI events... that is the location of the microphone on the surface of the blade. It can be seen Irom the plot that the majority of the advancing side BVI events occur in the azimuthal range tlr = 0 to tlr = 60. As the advance ratio increases, the spacing between the BVI events...

Mani, Somnath

2012-06-07

42

NOISE GENERATION OF BLADE–VORTEX RESONANCE  

Microsoft Academic Search

A numerical study of the aerodynamic noise generated when an airfoil\\/blade in a uniform flow is excited by an oncoming vortical flow is reported. The vortical flow is modelled by a series of flow convected discrete vortices representative of a Karman vortex street. Such noise generation problems due to fluid–blade interaction occur in helicopter rotor and turbomachinery blades. Interactions with

R. C. K. LEUNG; R. M. C. SO

2001-01-01

43

Noise Generation of Blade-Vortex Resonance  

Microsoft Academic Search

A numerical study of the aerodynamic noise generated when an airfoil\\/blade in a uniform flow is excited by an oncoming vortical flow is reported. The vortical flow is modelled by a series of flow convected discrete vortices representative of a Karman vortex street. Such noise generation problems due to fluid-blade interaction occur in helicopter rotor and turbomachinery blades. Interactions with

R. C. K. Leung; R. M. C. So

2001-01-01

44

Prediction and measurement of blade-vortex interaction loading  

NASA Technical Reports Server (NTRS)

An extensive quantity of airload measurements was obtained for a pressure-instrumented model of the BO-105 main rotor for a large number of higher-harmonic control (HHC) settings at Duits-Nederlandse Wind Tunnel (DNW). The wake geometry, vortex strength, and vortex core size were also measured through a laser light sheet technique and LDV. These results are used to verify the BVI airload prediction methodologies developed by AFDD, DLR, NASA Langley, and ONERA. The comparisons show that an accurate prediction of the blade motion and the wake geometry is the most important aspect of the BVI airload predictions.

Tung, Chee; Gallman, Judith M.; Kube, Roland; Brooks, Thomas F.; Rahier, Gilles

1995-01-01

45

Full-potential modeling of blade-vortex interactions  

NASA Technical Reports Server (NTRS)

A comparison is made of four different models for predicting the unsteady loading induced by a vortex passing close to an airfoil. (1) The first model approximates the vortex effect as a change in the airfoil angle of attack. (2) The second model is related to the first but, instead of imposing only a constant velocity on the airfoil, the distributed effect of the vortex is computed and used. This is analogous to a lifting surface method. (3) The third model is to specify a branch cut discontinuity in the potential field. The vortex is modeled as a jump in potential across the branch cut, the edge of which represents the center of the vortex. (4) The fourth method models the vortex expressing the potential as the sum of a known potential due to the vortex and an unknown perturbation due to the airfoil. The purpose of the current study is to investigate the four vortex models described above and to determine their relative merits and suitability for use in large three-dimensional codes.

Jones, H. E.; Caradonna, F. X.

1986-01-01

46

An Eulerian/Lagrangian method for computing blade/vortex impingement  

NASA Technical Reports Server (NTRS)

A combined Eulerian/Lagrangian approach to calculating helicopter rotor flows with concentrated vortices is described. The method computes a general evolving vorticity distribution without any significant numerical diffusion. Concentrated vortices can be accurately propagated over long distances on relatively coarse grids with cores only several grid cells wide. The method is demonstrated for a blade/vortex impingement case in 2D and 3D where a vortex is cut by a rotor blade, and the results are compared to previous 2D calculations involving a fifth-order Navier-Stokes solver on a finer grid.

Steinhoff, John; Senge, Heinrich; Yonghu, Wenren

1991-01-01

47

Numerical investigation of parallel airfoil-vortex interaction using large eddy simulation  

NASA Astrophysics Data System (ADS)

Helicopter Blade-Vortex Interaction (BVI) occurs under certain conditions of powered descent or during extreme maneuvering. The vibration and acoustic problems associated with the interaction of rotor tip vortices and the following blades are major aerodynamic concerns for the helicopter community. Researchers have performed numerous experimental and computational studies over the last two decades in order to gain a better understanding of the physical mechanisms involved in BVI. The most severe interaction, in terms of generated noise, happens when the vortex filament is parallel to the blade, thus affecting a great portion of it. The majority of the previous numerical studies of parallel BVI fall within a potential flow framework, therefore excluding all viscous phenomena. Some Navier-Stokes approaches using dissipative numerical methods in conjunction with RANS-type turbulence models have also been attempted, but with limited success. In this work, the situation is improved by increasing the fidelity of both the numerical method and the turbulence model. A kinetic-energy conserving finite-volume scheme using a collocated-mesh arrangement, specially designed for simulation of turbulence in complex geometries, was implemented. For the turbulence model, a cost-effective zonal hybrid RANS/LES technique is used. A BANS zone covers the boundary layers on the airfoil and the wake region behind, while the remainder of the flow field, including the region occupied by the vortex makes up the dynamic LES zone. The concentrated tip vortex is not attenuated as it is convected downstream and over a NACA 0012 airfoil. The lift, drag, moment and friction coefficients induced by the passage of the vortex are monitored in time and compared with experimental data.

Felten, Frederic N.

48

An adaptive mesh method for the simulation of Blade Vortex Interaction  

E-print Network

first consider a simple case with a convecting vortex in freestream. Finally, we apply tile techniques to examine the effectiveness of an active TEF on BVI in reducing the pressure perturbations at the airfoil leading edge. For the boundary motion due...

Kim, Kyu-Sup

2012-06-07

49

Parallel Vegetation Stripe Formation Through Hydrologic Interactions  

NASA Astrophysics Data System (ADS)

It has long been a challenge to theoretical ecologists to describe vegetation pattern formations such as the "tiger bush" stripes and "leopard bush" spots in Niger, and the regular maze patterns often observed in bogs in North America and Eurasia. To date, most of simulation models focus on reproducing the spot and labyrinthine patterns, and on the vegetation bands which form perpendicular to surface and groundwater flow directions. Various hypotheses have been invoked to explain the formation of vegetation patterns: selective grazing by herbivores, fire, and anisotropic environmental conditions such as slope. Recently, short distance facilitation and long distance competition between vegetation (a.k.a scale dependent feedback) has been proposed as a generic mechanism for vegetation pattern formation. In this paper, we test the generality of this mechanism by employing an existing, spatially explicit, advection-reaction-diffusion type model to describe the formation of regularly spaced vegetation bands, including those that are parallel to flow direction. Such vegetation patterns are, for example, characteristic of the ridge and slough habitat in the Florida Everglades and which are thought to have formed parallel to the prevailing surface water flow direction. To our knowledge, this is the first time that a simple model encompassing a nutrient accumulation mechanism along with biomass development and flow is used to demonstrate the formation of parallel stripes. We also explore the interactive effects of plant transpiration, slope and anisotropic hydraulic conductivity on the resulting vegetation pattern. Our results highlight the ability of the short distance facilitation and long distance competition mechanism to explain the formation of the different vegetation patterns beyond semi-arid regions. Therefore, we propose that the parallel stripes, like the other periodic patterns observed in both isotropic and anisotropic environments, are self-organized and form as a result of scale dependent feedback. Results from this study improve upon the current understanding on the formation of parallel stripes and provide a more general theoretical framework for future empirical and modeling efforts.

Cheng, Yiwei; Stieglitz, Marc; Turk, Greg; Engel, Victor

2010-05-01

50

Interactive scientific visualization and parallel display techniques  

Microsoft Academic Search

In this paper, we describe a new graphics environment for essentially real-time interactive visualization of computational fluid mechanics. Within this environment, the researcher may interactively examine fluid data on a framebuffer with animated flow visualization diagnostics which mimic those in the experimental laboratory. This provides an effective and interactive way to analyze the underlying physical mechanisms, and to compare results

James A. Sethian; J. B. Salem; A. F. Ghoniem

1988-01-01

51

Hydrogen and electricity: Parallels, interactions, and convergence  

Microsoft Academic Search

A future hydrogen economy would interact with and influence the electricity grid in numerous ways. This paper presents several concepts for understanding a hydrogen economy in the context of the co-evolution with the electricity sector and lays out some of the opportunities and challenges. H2 and electricity are complementary energy carriers that have distinct characteristics, which lead to more or

Christopher Yanga

52

Aeroacoustic interaction of a distributed vortex with a lifting Joukowski airfoil  

Microsoft Academic Search

A first principles computational aeroacoustics calculation of the flow and noise fields produced by the interaction of a distributed vortex with a lifting Joukowski airfoil is accomplished at the Reynolds number of 200. The case considered is that where the circulations of the vortex and the airfoil are of opposite sign, corresponding to blade vortex interaction on the retreating side

J. C. Hardin; S. L. Lamkin

1984-01-01

53

Nicotine and cannabinoids: parallels, contrasts and interactions.  

PubMed

After a brief outline of the nicotinic and cannabinoid systems, we review the interactions between the pharmacological effects of nicotine and cannabis, two of the most widely used drugs of dependence. These drugs are increasingly taken in combination, particularly among the adolescents and young adults. The review focuses on addiction-related processes, gateway and reverse gateway theories of addiction and therapeutic implications. It then reviews studies on the important period of adolescence, an area that is in urgent need of further investigation and in which the importance of sex differences is emerging. Three other areas of research, which might be particularly relevant to the onset and/or maintenance of dependence, are then reviewed. Firstly, the effects of the two drugs on anxiety-related behaviours are discussed and then their effects on food intake and cognition, two areas in which they have contrasting effects. Certain animal studies suggest that reinforcing effects are likely to be enhanced by joint consumption of nicotine and cannabis, as also may be anxiolytic effects. If this was the case in humans, the latter might be viewed as an advantage particularly by adolescent girls, although the increased weight gain associated with cannabis would be a disadvantage. The two drugs also have opposite effects on cognition and the possibility of long-lasting cognitive impairments resulting from adolescent consumption of cannabis is of particular concern. PMID:17049986

Viveros, Maria-Paz; Marco, Eva M; File, Sandra E

2006-01-01

54

An interactive parallel programming environment applied in atmospheric science  

NASA Technical Reports Server (NTRS)

This article introduces an interactive parallel programming environment (IPPE) that simplifies the generation and execution of parallel programs. One of the tasks of the environment is to generate message-passing parallel programs for homogeneous and heterogeneous computing platforms. The parallel programs are represented by using visual objects. This is accomplished with the help of a graphical programming editor that is implemented in Java and enables portability to a wide variety of computer platforms. In contrast to other graphical programming systems, reusable parts of the programs can be stored in a program library to support rapid prototyping. In addition, runtime performance data on different computing platforms is collected in a database. A selection process determines dynamically the software and the hardware platform to be used to solve the problem in minimal wall-clock time. The environment is currently being tested on a Grand Challenge problem, the NASA four-dimensional data assimilation system.

vonLaszewski, G.

1996-01-01

55

Parallel Graphics and Interactivity with the Scaleable Graphics Engine  

SciTech Connect

A parallel rendering environment is being developed to utilize the IBM Scaleable Graphics Engine (SGE), a hardware frame buffer for parallel computers. Goals of this software development effort include finding efficient ways of producing and displaying graphics generated on SP nodes and of assisting programmers in adapting or creating scientific simulation applications to use the SGE. Four software development phases are discussed utilize the SGE: tunneling, SMP Rendering, graphics API development using an OpenGL API implementation which utilizes the SGE in the parallel environment, and additions to the SGE-enabled OpenGL API implementation that uses threads. The SGE's ability to accept pixel data from multiple nodes simultaneously makes it a viable tool for use. With the performance observed in the test applications and performance optimizations gained programmers writing applications for IBM SPs and Linux clusters will be able to support high-speed output of graphics and be able to interact with data.

Perrine, Kenneth A.; Jones, Donald R.

2001-11-10

56

IPython: components for interactive and parallel computing across disciplines. (Invited)  

NASA Astrophysics Data System (ADS)

Scientific computing is an inherently exploratory activity that requires constantly cycling between code, data and results, each time adjusting the computations as new insights and questions arise. To support such a workflow, good interactive environments are critical. The IPython project (http://ipython.org) provides a rich architecture for interactive computing with: 1. Terminal-based and graphical interactive consoles. 2. A web-based Notebook system with support for code, text, mathematical expressions, inline plots and other rich media. 3. Easy to use, high performance tools for parallel computing. Despite its roots in Python, the IPython architecture is designed in a language-agnostic way to facilitate interactive computing in any language. This allows users to mix Python with Julia, R, Octave, Ruby, Perl, Bash and more, as well as to develop native clients in other languages that reuse the IPython clients. In this talk, I will show how IPython supports all stages in the lifecycle of a scientific idea: 1. Individual exploration. 2. Collaborative development. 3. Production runs with parallel resources. 4. Publication. 5. Education. In particular, the IPython Notebook provides an environment for "literate computing" with a tight integration of narrative and computation (including parallel computing). These Notebooks are stored in a JSON-based document format that provides an "executable paper": notebooks can be version controlled, exported to HTML or PDF for publication, and used for teaching.

Perez, F.; Bussonnier, M.; Frederic, J. D.; Froehle, B. M.; Granger, B. E.; Ivanov, P.; Kluyver, T.; Patterson, E.; Ragan-Kelley, B.; Sailer, Z.

2013-12-01

57

Interaction of unequal anti-parallel vortex tubes  

Microsoft Academic Search

A computational study is reported of the close interaction of nominally anti-parallel vortex tubes with unequal strengths, [Gamma]1 and [minus sign][Gamma]2, where [Gamma]2\\/[Gamma]1 [less-than-or-eq, slant] 1. The computations are performed using a spectral method, with periodic boundary conditions and vortex Reynolds number Re [identical with] [Gamma]1\\/v = 1500, and the vortices are perturbed by a wavelength for which the pair

J. S. Marshall; P. Brancher; A. Giovannini

2001-01-01

58

DSMC Investigation of Interacting Parallel Supersonic Free Jets  

NASA Astrophysics Data System (ADS)

Our interest in adjacent parallel jets is motivated by the relevance to the design of rocket propulsion systems. The direct simulation Monte Carlo (DSMC) method is the preferred method of analysis of rarefied compressible flows because of better accuracy compared to continuum prediction methods. In this paper, we apply the DSMC method to investigate the dynamics of three-dimensional flow of two interacting, parallel, supersonic free jets, including the resolution of the internal structure of the shock system. The jets come from two parallel orifices and exhaust into a low-pressure chamber. Bird's no-timing-counter scheme is used for the intermolecular collisions, while the variable-soft-sphere (VSS) molecular model is adopted for both monatomic and diatomic gases. Non-equilibrium effects are considered for the diatomic gases. The effects of the geometric arrangement of the orifices and the boundary pressure conditions are investigated and will be reported, as will the effects of the roughness of the cell network and the number of molecules in a cell.

Li, Wenhai; Ladeinde, Foluso

2004-11-01

59

Parallel Simulation of ElectronSolid Interactions Electron Microscopy Modeling  

E-print Network

* Parallel Computational Sciences Department, # Materials and Process Sciences Center Key Words: parallel the sample composition [Michael, et al. 1990]. A simpler, yet effective method for accomplishing composition data and to characterize electron microscope performance are briefly highlighted. #12; Page 2

Plimpton, Steve

60

Mutual interaction between parallel Gaussian electromagnetic beams in plasmas  

SciTech Connect

In this paper, the interaction between two Gaussian electromagnetic beams in a plasma has been investigated, when the axes of the two beams are initially (z=0) parallel along the z axis in the x-z plane; the beams are initially propagating in the z direction. For the three types of nonlinearities (viz., collisional, ponderomotive, and relativistic) the dielectric function has been expressed as a function of the irradiances of the two beams; this expression for the dielectric function has been substituted in the wave equation and a solution of the resulting nonlinear equation obtained in the paraxial approximation. The paraxial approximation is justified since the phenomena of interest occur when the beams are initially close ({radical}(2)x{sub 0}{<=}r{sub 0}). Further, the absorption of the beam in the plasma has been neglected, which is justified when the electron collision frequency is much less than the frequencies of the beams. Second-order coupled ordinary differential equations have been obtained for the distance between the centers of the beams and the beam widths in the x and y directions as a function of the distance of propagation along the z axis. The equations have been solved numerically for a range of parameters and a discussion of the results is presented.

Sodha, Mahendra Singh; Agarwal, Sujeet Kumar; Sharma, Ashutosh [Disha Academy of Research and Education, Disha Crown, Katchna Road, Shankar Nagar, Raipur-492007 (India); DST Project, Department of Education Building, Lucknow University, Lucknow-226007 (India)

2006-10-15

61

VisIt: Interactive Parallel Visualization and Graphical Analysis Tool  

NASA Astrophysics Data System (ADS)

VisIt is a free interactive parallel visualization and graphical analysis tool for viewing scientific data on Unix and PC platforms. Users can quickly generate visualizations from their data, animate them through time, manipulate them, and save the resulting images for presentations. VisIt contains a rich set of visualization features so that you can view your data in a variety of ways. It can be used to visualize scalar and vector fields defined on two- and three-dimensional (2D and 3D) structured and unstructured meshes. VisIt was designed to handle very large data set sizes in the terascale range and yet can also handle small data sets in the kilobyte range. See the table below for more details about the tool's features. VisIt was developed by the Department of Energy (DOE) Advanced Simulation and Computing Initiative (ASCI) to visualize and analyze the results of terascale simulations. It was developed as a framework for adding custom capabilities and rapidly deploying new visualization technologies. Although the primary driving force behind the development of VisIt was for visualizing terascale data, it is also well suited for visualizing data from typical simulations on desktop systems.

Department Of Energy (DOE) Advanced Simulation; Computing Initiative (ASCI)

2011-03-01

62

Parallel Graphics and Interactivity with the Scaleable Graphics Engine  

Microsoft Academic Search

A parallel rendering environment is being developed to utilize the IBM Scaleable Graphics Engine (SGE), a hardware frame buffer for parallel computers. Goals of this software development effort include finding efficient ways of producing and displaying graphics generated on IBM SP nodes and of assisting programmers in adapting or creating scientific simulation applications to use the SGE. Four software development

Kenneth A. Perrine; Donald R. Jones

2001-01-01

63

Parallel graphics and interactivity with the scaleable graphics engine  

Microsoft Academic Search

A parallel rendering environment is being developed to utilize the IBM Scaleable Graphics Engine (SGE), a hardware frame buffer for parallel computers. Goals of this software development effort include finding efficient ways of producing and displaying graphics generated on IBM SP nodes and of assisting programmers in adapting or creating scientific simulation applications to use the SGE. Four software development

Kenneth A. Perrine; Donald R. Jones

2001-01-01

64

STAR/MPI: Binding a Parallel Library to Interactive Symbolic Algebra Systems  

E-print Network

interactive languages besides GCL and GAP, from which comes the name STAR/MPI, or #3;/MPI. STAR/MPI includes/MPI can immediately take advantage of such parallel architectures. The name STAR/MPI (\\#3;/MPI") has beenSTAR/MPI: Binding a Parallel Library to Interactive Symbolic Algebra Systems Gene Cooperman 1 gene

Cooperman, Gene

65

DSMC Investigation of Interacting Parallel Supersonic Free Jets  

Microsoft Academic Search

Our interest in adjacent parallel jets is motivated by the relevance to the design of rocket propulsion systems. The direct simulation Monte Carlo (DSMC) method is the preferred method of analysis of rarefied compressible flows because of better accuracy compared to continuum prediction methods. In this paper, we apply the DSMC method to investigate the dynamics of three-dimensional flow of

Wenhai Li; Foluso Ladeinde

2004-01-01

66

STAR/MPI: Binding a Parallel Library to Interactive Symbolic Algebra Systems  

E-print Network

of MPI to interactivearchitectures. The name * *STAR/MPI ("*/MPI") has been languages. (MPI already has the name STAR/MPI, or */MPI.Because there is such a varie* *ty of parallel systems, it is STAR STAR/MPI: Binding a Parallel Library to Interactive

Cooperman, Gene

67

An Architecture for Web-Based Interaction and Steering of Adaptive Parallel\\/Distributed Applications  

Microsoft Academic Search

This paper presents an environment for Web-based interaction and steering of adaptive parallel\\/distributed scientific applications. The architecture is composed of detachable thin-clients at the front-end, a network of Java interaction servers i n the middle, and a control network of sensors, actuators, interaction agents, and an application interaction proxy, superimposed on the application data-network, at the back-end. There are three

Rajeev Muralidhar; Samian Kaur; Manish Parashar

2000-01-01

68

Experiences Using the ParaScope Editor: an Interactive Parallel Programming Tool  

Microsoft Academic Search

The ParaScope Editor is an interactive parallel pro- gramming tool that assists knowledgeable users in de- veloping scientific Fortran programs. It displays the re- sults of sophisticated program analyses, provides a set of powerful interactive transformations, and supports program editing. This paper summarizes experiences of scientific programmers and tool designers using the ParaScope Editor. We evaluate existing features and describe

Mary W. Hall; Timothy J. Harvey; Ken Kennedy; Nathaniel McIntosh; Kathryn S. McKinley; Jeffrey D. Oldham; Michael H. Paleczny; Gerald Roth

1993-01-01

69

An interactive parallel coordinates technique applied to a tropical cyclone climate analysis  

Microsoft Academic Search

A highly interactive visual analysis system is presented that is based on an enhanced variant of parallel coordinates — a multivariate information visualization technique. The system combines many variations of previously described visual interaction techniques such as dynamic axis scaling, conjunctive visual queries, statistical indicators, and aerial perspective shading. The system capabilities are demonstrated on a hurricane climate data set.

Chad A. Steed; Patrick J. Fitzpatrick; T. J. Jankun-Kelly; Amber N. Yancey; J. Edward Swan II

2009-01-01

70

An Interactive Object Infrastructure for Computational Steering of Parallel\\/Distributed Simulations  

Microsoft Academic Search

This paper presents the design, implementation and experimental eval-uation of DIOS (Distributed Interactive Object Substrate), an interactiveobject infrastructure to enable the runtime monitoring, interaction andcomputational steering of parallel and distributed applications. DIOS en-ables application objects (data structures, algorithm) to be enhanced withsensors and actuators so that they can be interrogated and controlled

Rajeev Muralidhar; Manish Parashar

2000-01-01

71

STAR/MPI: Binding a Parallel Library to Interactive Symbolic Algebra Systems  

E-print Network

interactive languages besides GCL and GAP, from which comes the name STAR/MPI, or \\Lambda/MPI. STAR. The name STAR/MPI (``\\Lambda/MPI'') has been chosen with the idea that ``\\Lambda'' can be replacedSTAR/MPI: Binding a Parallel Library to Interactive Symbolic Algebra Systems Gene Cooperman 1 gene

Cooperman, Gene

72

Parallel and Adaptive Methods for Fluid-Structure-Interactions  

Microsoft Academic Search

\\u000a The new flow solver Quadflow, developed within the SFB 401, has been designed for investigating flows around airfoils and\\u000a simulating the interaction of the structural dynamics and aerodynamics. This article addresses the following issues arising\\u000a in this context. After identifying proper coupling conditions and settling the well-posedness of the resulting coupled fluid-structure\\u000a problem, suitable strategies for successively applying flow and

Josef Ballmann; Marek Behr; Kolja Brix; Wolfgang Dahmen; Christoph Hohn; Ralf Massjung; Sorana Melian; Siegfried Müller; Gero Schieffer

73

A study on interaction control for seismic response of parallel structures  

Microsoft Academic Search

A structure response control approach which uses controlled interactions between two parallel structures (a primary structure and an auxiliary structure) to reduce the seismic response of the primary structure (P-structure) during earthquake excitation, is proposed. Three strategies of the control approach, including optimal passive control, semi-active control, and active control are examined. The optimum passive-coupling elements between two parallel structures

Hongping Zhu; Yinping Wen; Hirokazu Iemura

2001-01-01

74

A component-based parallel infrastructure for the simulation of fluid-structure interaction  

Microsoft Academic Search

The Uintah computational framework is a component-based infrastructure, designed for highly parallel simulations of complex\\u000a fluid–structure interaction problems. Uintah utilizes an abstract representation of parallel computation and communication\\u000a to express data dependencies between multiple physics components. These features allow parallelism to be integrated between\\u000a multiple components while maintaining overall scalability. Uintah provides mechanisms for load-balancing, data communication,\\u000a data I\\/O, and

Steven G. Parker; James Guilkey; Todd Harman

2006-01-01

75

SPECIFIC ABSORPTION RATE BENEFITS OF INCLUDING MEASURED ELECTRIC FIELD INTERACTIONS IN PARALLEL EXCITATION PULSE DESIGN  

PubMed Central

Specific absorption rate management and excitation fidelity are key aspects of radio frequency pulse design for parallel transmission at ultra high magnetic field strength. The design of radio frequency pulses for multiple channels is often based on the solution of regularized least squares optimization problems for which a regularization term is typically selected to control the integrated or peak pulse waveform amplitude. Unlike single channel transmission, the specific absorption rate of parallel transmission is significantly influenced by interferences between the electric fields associated with the individual transmission elements, which a conventional regularization term does not take into account. This work explores the effects upon specific absorption rate of incorporating experimentally measurable electric field interactions into parallel transmission pulse design. Results of numerical simulations and phantom experiments show that the global specific absorption rate during parallel transmission decreases when electric field interactions are incorporated into pulse design optimization. The results also show that knowledge of electric field interactions enables robust prediction of the net power delivered to the sample or subject by parallel radio frequency pulses before they are played out on a scanner. PMID:22135040

Deniz, Cem Murat; Alon, Leeor; Brown, Ryan; Sodickson, Daniel K.; Zhu, Yudong

2011-01-01

76

A parallel iterative partitioned coupling analysis system for large-scale acoustic fluid-structure interactions  

NASA Astrophysics Data System (ADS)

In many engineering fields, dynamic response in fluid-structure interaction (FSI) is important, and some of the FSI phenomena are treated as acoustic FSI (AFSI) problems. Dynamic interactions between fluids and structures may change dynamic characteristics of the structure and its response to external excitation parameters such as seismic loading. This paper describes a parallel coupling analysis system for large-scale AFSI problems using iterative partitioned coupling techniques. We employ an open source parallel finite element analysis system called ADVENTURE, which adopts an efficient preconditioned iterative linear algebraic solver. In addition, we have recently developed a parallel coupling tool called ADVENTURE_Coupler to efficiently handle interface variables in various parallel computing environments. We also employ the Broyden method for updating interface variables to attain robust and fast convergence of fixed-point iterations. This paper describes key features of the coupling analysis system developed, and we perform tests to validate its performance for several AFSI problems. The system runs efficiently in a parallel environment, and it is capable of analyzing three-dimensional-complex-shaped structures with more than 20 million degrees-of-freedom (DOFs). Its numerical results also show good agreement with experimental results.

Kataoka, Shunji; Minami, Satsuki; Kawai, Hiroshi; Yamada, Tomonori; Yoshimura, Shinobu

2014-06-01

77

Two-dimensional interaction of vortices with a blade  

NASA Technical Reports Server (NTRS)

The problem of blade-vortex interaction is studied experimentally and numerically. Vortices are generated in the laboratory by pitching an airfoil upstream of the model. LDV measurements are obtained in the neighborhood of the leading edge of the airfoil. Ensemble-averaged velocity vector fields and vorticity contours are thus constructed. A vortex is modeled numerically by a cloud of discrete ideal point vortices. The problem is solved via a Joukowski transformation. The interaction of distributed vorticity with the leading edge of the airfoil is examined.

Poling, David R.; Telionis, Demetri P.; Wilder, Michael C.

1988-01-01

78

Parallel and perpendicular diffusion coefficients of energetic particles interacting with shear Alfvén waves  

NASA Astrophysics Data System (ADS)

We investigate the interaction of energetic particles with parallel propagating shear Alfvén waves. We use analytical tools as well as test-particle simulations. The analytical derivation of the parallel diffusion coefficient is done by employing quasi-linear theory, a well-known tool in diffusion theory. The perpendicular diffusion coefficient, however, is derived by employing the unifield non-linear transport theory. This is the first time we derive a simple analytical form of the perpendicular mean free path based on the latter theory. We perform the simulations and we show that quasi-linear theory works well for parallel diffusion in Alfvénic slab turbulence as expected. We also show that the unified non-linear transport theory perfectly describes perpendicular diffusion for the turbulence model used here.

Hussein, M.; Shalchi, A.

2014-11-01

79

Interactive Parallel Data Analysis within Data-Centric Cluster Facilities using the IPython Notebook  

NASA Astrophysics Data System (ADS)

The data deluge is making traditional analysis workflows for many researchers obsolete. Support for parallelism within popular tools such as matlab, IDL and NCO is not well developed and rarely used. However parallelism is necessary for processing modern data volumes on a timescale conducive to curiosity-driven analysis. Furthermore, for peta-scale datasets such as the CMIP5 archive, it is no longer practical to bring an entire dataset to a researcher's workstation for analysis, or even to their institutional cluster. Therefore, there is an increasing need to develop new analysis platforms which both enable processing at the point of data storage and which provides parallelism. Such an environment should, where possible, maintain the convenience and familiarity of our current analysis environments to encourage curiosity-driven research. We describe how we are combining the interactive python shell (IPython) with our JASMIN data-cluster infrastructure. IPython has been specifically designed to bridge the gap between the HPC-style parallel workflows and the opportunistic curiosity-driven analysis usually carried out using domain specific languages and scriptable tools. IPython offers a web-based interactive environment, the IPython notebook, and a cluster engine for parallelism all underpinned by the well-respected Python/Scipy scientific programming stack. JASMIN is designed to support the data analysis requirements of the UK and European climate and earth system modeling community. JASMIN, with its sister facility CEMS focusing the earth observation community, has 4.5 PB of fast parallel disk storage alongside over 370 computing cores provide local computation. Through the IPython interface to JASMIN, users can make efficient use of JASMIN's multi-core virtual machines to perform interactive analysis on all cores simultaneously or can configure IPython clusters across multiple VMs. Larger-scale clusters can be provisioned through JASMIN's batch scheduling system. Outputs can be summarised and visualised using the full power of Python's many scientific tools, including Scipy, Matplotlib, Pandas and CDAT. This rich user experience is delivered through the user's web browser; maintaining the interactive feel of a workstation-based environment with the parallel power of a remote data-centric processing facility.

Pascoe, S.; Lansdowne, J.; Iwi, A.; Stephens, A.; Kershaw, P.

2012-12-01

80

Interferometer Development for Study of Interactions between Flames on Parallel Solid Surfaces  

NASA Technical Reports Server (NTRS)

The interactions between flames spreading over parallel solid sheets of paper are being studied in normal gravity and in microgravity. This geometry provides interesting opportunities to study the interaction of radiative and diffusive transport mechanisms on the spread process. These transport mechanisms are changed when the flame interacts with other flames. Most practical heterogeneous combustion processes involve interacting discrete burning fuel elements, consequently, the study of these interactions is of practical significance. Owing largely to this practical importance, flame interactions have been an area of active research, however microgravity research has been largely limited to droplets. Consideration of flame spread over parallel solid surfaces has been limited to 1-g studies. To study the conductive transport in these flames, an interferometer system has been developed for use in the drop tower. The system takes advantage of a single beam interferometer: Point Diffraction Interferometry (PDI) which uses a portion of the light through the test section to provide the reference beam. Like other interferometric and Schlieren systems, it is a line of sight measurement and is subject to the usual edge and concentration effects. The advantage over Schlieren and shearing interferometry systems is that the fringes are lines of constant index of refraction rather than of its gradient so the images are more readily interpreted. The disadvantage is that it is less able to accommodate a range of temperature gradients.

Goldmeer, J. S.; Urban, D. L.; Yuan, Z. G.

1999-01-01

81

Propeller tip vortex interactions  

NASA Technical Reports Server (NTRS)

Propeller wakes interacting with aircraft aerodynamic surfaces are a source of noise and vibration. For this reason, flow visualization work on the motion of the helical tip vortex over a wing and through the second stage of a counterrotation propeller (CRP) has been pursued. Initially, work was done on the motion of a propeller helix as it passes over the center of a 9.0 aspect ratio wing. The propeller tip vortex experiences significant spanwise displacements when passing across a lifting wing. A stationary propeller blade or stator was installed behind the rotating propeller to model the blade vortex interaction in a CRP. The resulting vortex interaction was found to depend on the relative vortex strengths and vortex sign.

Johnston, Robert T.; Sullivan, John P.

1990-01-01

82

3D Parallel Simulation Model of Continuous Beam Electron Cloud Interactions  

Microsoft Academic Search

Long-term beam-electron cloud interaction is modeled with a 3D parallel continuous model originally developed for plasma wakefield acceleration modeling. The simulation results are compared with the two macro-particle model for strong head-tail instability. The two macro- particle model qualitatively captures some of the instability features of the beam. The code is then used to model and make predictions for the

A. Z. Ghalam; T. Katsouleas; V. K. Decyk; C. K. Huang; W. B. Mori; G. Rumolo; E. Benedetto; F. Zimmermann

2005-01-01

83

COMPUTATIONAL MODELING OF NONLINEAR SOIL-STRUCTURE INTERACTION ON PARALLEL COMPUTERS  

Microsoft Academic Search

SUMMARY In order to satisfactorily reproduce the Soil-Structure Interaction (SSI) effects under earthquake loading, it is often necessary to model a large domain of the soil surrounding the structure of interest. High spatial\\/temporal resolution is another challenge in analyzing these models. A new parallel nonlinear finite element program, ParCYCLIC, is employed to study such high fidelity large-scale SSI models. ParCYCLIC

Jinchi LU; Zhaohui YANG; Liangcai HE; Jun PENG; Ahmed ELGAMAL; Kincho H. LAW

84

Parallel implementation of three-dimensional molecular dynamic simulation for laser-cluster interaction  

SciTech Connect

The objective of this article is to report the parallel implementation of the 3D molecular dynamic simulation code for laser-cluster interactions. The benchmarking of the code has been done by comparing the simulation results with some of the experiments reported in the literature. Scaling laws for the computational time is established by varying the number of processor cores and number of macroparticles used. The capabilities of the code are highlighted by implementing various diagnostic tools. To study the dynamics of the laser-cluster interactions, the executable version of the code is available from the author.

Holkundkar, Amol R. [Department of Physics, Birla Institute of Technology and Science, Pilani-333 031 (India)] [Department of Physics, Birla Institute of Technology and Science, Pilani-333 031 (India)

2013-11-15

85

Parallel processing  

SciTech Connect

This book provides a introduction to the fundamental principles and practice of parallel processing. After a general introduction to the many facets of parallelism, the first part of the book is devoted to the development of a coherent theoretical framework. Particular attention is paid to the modeling, semantics and complexity of interacting parallel processes. The second part of the book considers the more practical aspects such as parallel processor architecture, parallel and distributed programming, and concurrent transaction handling in databases.

Krishnamurthy, E.V. (Waikato Univ., Hamilton (New Zealand))

1989-01-01

86

Three-wave interactions of dispersive plasma waves propagating parallel to the magnetic field  

E-print Network

Three-wave interactions of plasma waves propagating parallel to the mean magnetic field at frequencies below the electron cyclotron frequency are considered. We consider Alfv\\'en--ion-cyclotron waves, fast-magnetosonic--whistler waves, and ion-sound waves. Especially the weakly turbulent low-beta plasmas like the solar corona are studied, using the cold-plasma dispersion relation for the transverse waves and the fluid-description of the warm plasma for the longitudinal waves. We analyse the resonance conditions for the wave frequencies $\\omega$ and wavenumbers $k$, and the interaction rates of the waves for all possible combinations of the three wave modes, and list those reactions that are not forbidden.

F. Spanier; R. Vainio

2008-10-28

87

Electromagnetic semitransparent $?$-function plate: Casimir interaction energy between parallel infinitesimally thin plates  

E-print Network

We derive boundary conditions for electromagnetic fields on a $\\delta$-function plate. The optical properties of such a plate are shown to necessarily be anisotropic in that they only depend on the transverse properties of the plate. We unambiguously obtain the boundary conditions for a perfectly conducting $\\delta$-function plate in the limit of infinite dielectric response. We show that a material does not "optically vanish" in the thin-plate limit. The thin-plate limit of a plasma slab of thickness $d$ with plasma frequency $\\omega_p^2=\\zeta_p/d$ reduces to a $\\delta$-function plate for frequencies ($\\omega=i\\zeta$) satisfying $\\zeta d \\ll \\sqrt{\\zeta_p d} \\ll 1$. We show that the Casimir interaction energy between two parallel perfectly conducting $\\delta$-function plates is the same as that for parallel perfectly conducting slabs. Similarly, we show that the interaction energy between an atom and a perfect electrically conducting $\\delta$-function plate is the usual Casimir-Polder energy, which is verified by considering the thin-plate limit of dielectric slabs. The "thick" and "thin" boundary conditions considered by Bordag are found to be identical in the sense that they lead to the same electromagnetic fields.

Prachi Parashar; Kimball A. Milton; K. V. Shajesh; M. Schaden

2012-06-01

88

Rotor-vortex interaction noise  

NASA Technical Reports Server (NTRS)

A theoretical and experimental study was conducted to develop a validated first principles analysis for predicting noise generated by helicopter main-rotor shed vortices interacting with the tail rotor. The generalized prediction procedure requires a knowledge of the incident vortex velocity field, rotor geometry, and rotor operating conditions. The analysis includes compressibility effects, chordwise and spanwise noncompactness, and treats oblique intersections with the blade planform. Assessment of the theory involved conducting a model rotor experiment which isolated the blade-vortex interaction noise from other rotor noise mechanisms. An isolated tip vortex, generated by an upstream semispan airfoil, was convected into the model tail rotor. Acoustic spectra, pressure signatures, and directivity were measured. Since assessment of the acoustic prediction required a knowledge of the vortex properties, blade-vortes intersection angle, intersection station, vortex stength, and vortex core radius were documented. Ingestion of the vortex by the rotor was experimentally observed to generate harmonic noise and impulsive waveforms.

Schlinker, R. H.; Amiet, R. K.

1983-01-01

89

Discovery of protein interactions using parallel analysis of translated ORFs (PLATO).  

PubMed

Parallel analysis of translated open reading frames (ORFs) (PLATO) can be used for the unbiased discovery of interactions between full-length proteins encoded by a library of 'prey' ORFs and surface-immobilized 'bait' antibodies, polypeptides or small-molecular-weight compounds. PLATO uses ribosome display (RD) to link ORF-derived mRNA molecules to the proteins they encode, and recovered mRNA from affinity enrichment is subjected to analysis using massively parallel DNA sequencing. Compared with alternative in vitro methods, PLATO provides several advantages including library size and cost. A unique advantage of PLATO is that an alternative reverse transcription-quantitative PCR (RT-qPCR) protocol can be used to test binding of specific, individual proteins. To illustrate a typical experimental workflow, we demonstrate PLATO for the identification of the immune target of serum antibodies from patients with inclusion body myositis (IBM). Beginning with an ORFeome library in an RD vector, the protocol can produce samples for deep sequencing or RT-qPCR within 4 d. PMID:24336473

Larman, H Benjamin; Liang, Anthony C; Elledge, Stephen J; Zhu, Jian

2014-01-01

90

Macroparticle simulation of collisionless parallel shocks generated by solar wind and planetary plasma interactions  

NASA Astrophysics Data System (ADS)

An implicit-particle simulation of the collisionless parallel shock created at the interface between an injected beam and a stationary plasma is performed in one-dimensional geometry. The solar wind plasma, which consists of ions and electrons, is injected into a stationary dense plasma that corresponds to the planetary ionosphere. Electromagnetic waves with right-hand circular polarization that propagate upstream (R- waves) are generated at the interface of the two plasmas, which decelerate the solar wind to form a shock. The shock transition region is not monotonic but consists of two distinct regions, a pedestal and a shock ramp. The transition region, which contains the ionopause, is a few thousand electron skin depths long. The parallel shock varies in time and periodically collapses and re-forms. The right-hand circularly polarized electromagnetic waves that propagate downstream (R+ waves) are excited at the shock ramp. Nonlinear wave-particle interaction between the solar wind and the R+ waves causes wave condensation and density modulation. These R+ waves may be sweeping away the downstream plasma to suppress its thermal diffusion across the shock. The electrons at the shock ramp exhibit a flat-topped velocity distribution along the magnetic field owing to the ion acoustic-like electrostatic waves.

Shimazu, H.; Machida, S.; Tanaka, M.

1996-04-01

91

Parallel-plate flow chamber for studies of 3D flow-endothelium interaction.  

PubMed

Flow induced shear stress influences vascular cellular biology and pathophysiology in numerous ways. Previous in vitro studies on interactions between flow and endothelial cells using parallel-plate flow chambers involve two-dimensional flows, whereas flows in larger vessels are commonly three-dimensional. We have constructed a parallel plate flow chamber with a backward facing step aligned oblique to the axis of the chamber. Flow visualisation by steady injection of ink through a hypodermic tube reveals swirling flow in the recirculation region downstream of the step. At given angles of the step, theta; (to the axis of the chamber), the pitch of the swirl and the width of the separation region, as measured in the direction perpendicular to the step, increase with the Reynolds number (Re). On the other hand, at given values of Re, reduction of theta; results in increases in the swirl pitch but decreases in the width of the separation zone. Furthermore, clearance time of ink from the separation region is shorter with an oblique step than a perpendicular one at given Re. Computer simulation confirms the 3D swirling flow created by the oblique step and provides detailed distribution of wall shear stresses in the flow chamber. PMID:12122250

Watkins, N V; Caro, C G; Wang, W

2002-01-01

92

Parallel computation of fluid-structural interactions using high resolution upwind schemes  

NASA Astrophysics Data System (ADS)

An efficient and accurate solver is developed to simulate the non-linear fluid-structural interactions in turbomachinery flutter flows. A new low diffusion E-CUSP scheme, Zha CUSP scheme, is developed to improve the efficiency and accuracy of the inviscid flux computation. The 3D unsteady Navier-Stokes equations with the Baldwin-Lomax turbulence model are solved using the finite volume method with the dual-time stepping scheme. The linearized equations are solved with Gauss-Seidel line iterations. The parallel computation is implemented using MPI protocol. The solver is validated with 2D cases for its turbulence modeling, parallel computation and unsteady calculation. The Zha CUSP scheme is validated with 2D cases, including a supersonic flat plate boundary layer, a transonic converging-diverging nozzle and a transonic inlet diffuser. The Zha CUSP2 scheme is tested with 3D cases, including a circular-to-rectangular nozzle, a subsonic compressor cascade and a transonic channel. The Zha CUSP schemes are proved to be accurate, robust and efficient in these tests. The steady and unsteady separation flows in a 3D stationary cascade under high incidence and three inlet Mach numbers are calculated to study the steady state separation flow patterns and their unsteady oscillation characteristics. The leading edge vortex shedding is the mechanism behind the unsteady characteristics of the high incidence separated flows. The separation flow characteristics is affected by the inlet Mach number. The blade aeroelasticity of a linear cascade with forced oscillating blades is studied using parallel computation. A simplified two-passage cascade with periodic boundary condition is first calculated under a medium frequency and a low incidence. The full scale cascade with 9 blades and two end walls is then studied more extensively under three oscillation frequencies and two incidence angles. The end wall influence and the blade stability are studied and compared under different frequencies and incidence angles. The Zha CUSP schemes are the first time to be applied in moving grid systems and 2D and 3D calculations. The implicit Gauss-Seidel iteration with dual time stepping is the first time to be used for moving grid systems. The NASA flutter cascade is the first time to be calculated in full scale.

Hu, Zongjun

93

Beowulf Analysis Symbolic INterface BASIN: Interactive Parallel Data Analysis for Everyone  

E-print Network

The advent of affordable parallel computers such as Beowulf PC clusters and, more recently, of multi-core PCs has been highly beneficial for a large number of scientists and smaller institutions that might not otherwise have access to substantial computing facilities. However, there has not been an analogous progress in the development and dissemination of parallel software: scientists need the expertise to develop parallel codes and have to invest a significant amount of time in the development of tools even for the most common data analysis tasks. We describe the Beowulf Analysis Symbolic INterface (BASIN) a multi-user parallel data analysis and visualization framework. BASIN is aimed at providing scientists with a suite of parallel libraries for astrophysical data analysis along with general tools for data distribution and parallel operations on distributed data to allow them to easily develop new parallel libraries for their specific tasks.

Vesperini, Enrico; McMillan, Stephen L W; Dura, James; Jones, Douglas

2008-01-01

94

Beowulf Analysis Symbolic INterface BASIN: Interactive Parallel Data Analysis for Everyone  

E-print Network

The advent of affordable parallel computers such as Beowulf PC clusters and, more recently, of multi-core PCs has been highly beneficial for a large number of scientists and smaller institutions that might not otherwise have access to substantial computing facilities. However, there has not been an analogous progress in the development and dissemination of parallel software: scientists need the expertise to develop parallel codes and have to invest a significant amount of time in the development of tools even for the most common data analysis tasks. We describe the Beowulf Analysis Symbolic INterface (BASIN) a multi-user parallel data analysis and visualization framework. BASIN is aimed at providing scientists with a suite of parallel libraries for astrophysical data analysis along with general tools for data distribution and parallel operations on distributed data to allow them to easily develop new parallel libraries for their specific tasks.

Enrico Vesperini; David M. Goldberg; Stephen L. W. McMillan; James Dura; Douglas Jones

2008-04-29

95

Experimental Studies of the Interaction Between a Parallel Shear Flow and a Directionally-Solidifying Front  

NASA Technical Reports Server (NTRS)

It has long been recognized that flow in the melt can have a profound influence on the dynamics of a solidifying interface and hence the quality of the solid material. In particular, flow affects the heat and mass transfer, and causes spatial and temporal variations in the flow and melt composition. This results in a crystal with nonuniform physical properties. Flow can be generated by buoyancy, expansion or contraction upon phase change, and thermo-soluto capillary effects. In general, these flows can not be avoided and can have an adverse effect on the stability of the crystal structures. This motivates crystal growth experiments in a microgravity environment, where buoyancy-driven convection is significantly suppressed. However, transient accelerations (g-jitter) caused by the acceleration of the spacecraft can affect the melt, while convection generated from the effects other than buoyancy remain important. Rather than bemoan the presence of convection as a source of interfacial instability, Hurle in the 1960s suggested that flow in the melt, either forced or natural convection, might be used to stabilize the interface. Delves considered the imposition of both a parabolic velocity profile and a Blasius boundary layer flow over the interface. He concluded that fast stirring could stabilize the interface to perturbations whose wave vector is in the direction of the fluid velocity. Forth and Wheeler considered the effect of the asymptotic suction boundary layer profile. They showed that the effect of the shear flow was to generate travelling waves parallel to the flow with a speed proportional to the Reynolds number. There have been few quantitative, experimental works reporting on the coupling effect of fluid flow and morphological instabilities. Huang studied plane Couette flow over cells and dendrites. It was found that this flow could greatly enhance the planar stability and even induce the cell-planar transition. A rotating impeller was buried inside the sample cell, driven by an outside rotating magnet, in order to generate the flow. However, it appears that this was not a well-controlled flow and may also have been unsteady. In the present experimental study, we want to study how a forced parallel shear flow in a Hele-Shaw cell interacts with the directionally solidifying crystal interface. The comparison of experimental data show that the parallel shear flow in a Hele-Shaw cell has a strong stabilizing effect on the planar interface by damping the existing initial perturbations. The flow also shows a stabilizing effect on the cellular interface by slightly reducing the exponential growth rate of cells. The left-right symmetry of cells is broken by the flow with cells tilting toward the incoming flow direction. The tilting angle increases with the velocity ratio. The experimental results are explained through the parallel flow effect on lateral solute transport. The phenomenon of cells tilting against the flow is consistent with the numerical result of Dantzig and Chao.

Zhang, Meng; Maxworthy, Tony

1999-01-01

96

Nucleic Acids Research, 1993, Vol. 21, No. 22 5085-5091 Structure and drug interactions of parallel-stranded DNA  

E-print Network

with the corresponding aps- DNAs. We studied the interaction of ps-DNA with three non- intercalating drugs (netropsin-stranded DNA studied by infrared spectroscopy and fluorescence Hartmut Fritzsche, Alain Akhebat1, Eliane 25-mer parallel- stranded DNAs (ps-DNA) have been studied. We have used ps-DNAs containing either

Rippe, Karsten

97

A Tool for On-line Visualization and Interactive Steering of Parallel HPC Applications  

Microsoft Academic Search

Tools for parallel systems today range from specification over debugging to performance analysis and more. Typ- ically, they help the programmers of parallel algorithms from the early development stages to a certain level of pro- gram optimization. However, in HPC ( High Performance Computing) today the end-user of massively parallel CFD (ComputationalFluid Dynamics)-programs has little or no support in his

Sabine Rathmayer; Michael Lenke

1997-01-01

98

An experimental investigation of the chopping of helicopter main rotor tip vortices by the tail rotor  

Microsoft Academic Search

The chopping of helicopter main rotor tip vortices by the tail rotor was experimentally investigated. This is a problem of blade vortex interaction (BVI) at normal incidence where the vortex is generally parallel to the rotor axis. The experiment used a model rotor and an isolated vortex and was designed to isolate BVI noise from other types of rotor noise.

A. R. Ahmadi

1984-01-01

99

Parallel History Matching and Associated Forecast at the Center for Interactive Smart Oilfield Technologies  

Microsoft Academic Search

We have developed a parallel and distributed computing framework to solve an inverse problem, which involves massive data sets and is of great impor- tance to petroleum industry. A Monte Carlo method, combined with proxies to avoid excessive data processing, is employed to identify reservoir simulation models that best match the oilfield production history. Subsequently, the selected models are used

Ken-ichi Nomura; Rajiv K. Kalia; Aiichiro Nakano; Priya Vashishta; Jorge L. Landa

2005-01-01

100

Kedama: A GUI-Based Interactive Massively Parallel Particle Programming System  

Microsoft Academic Search

Decentralized and complex systems can be powerful tools for modeling concepts in mathematics, science and engineering. Star Logo and NetLogo were the first systems to allow middle and high school children to build dynamic models from many thousands of programmable particles. This has inspired Kedama: an authoring system that simplifies the scripting and construction of massively parallel models to allow

Yoshiki Ohshima; Twin Sun

2005-01-01

101

Expression Profiles Reveal Parallel Evolution of Epistatic Interactions Involving the CRP Regulon in Escherichia coli  

Microsoft Academic Search

The extent and nature of epistatic interactions between mutations are issues of fundamental importance in evolutionary biology. However, they are difficult to study and their influence on adaptation remains poorly understood. Here, we use a systems-level approach to examine epistatic interactions that arose during the evolution of Escherichia coli in a defined environment. We used expression arrays to compare the

Tim F. Cooper; Susanna K. Remold; Richard E. Lenski; Dominique Schneider

2008-01-01

102

Model calculations of the interaction of two parallel antiaromatic 4n ?-electron systems  

PubMed Central

The nature of the interaction between decks of a pentalene dimer and an s-indacene dimer has been studied by semi-empirical MNDO/1 and MINDO/3 calculations for distances between decks of from 5 Å to 2 Å. In contradiction to qualitative predictions from a frontier orbital analysis, it is found that the 4n-4n ?-electron interaction between decks for such dimers is destabilizing for distances exceeding about 2.5 Å. PMID:16593458

Bohm, Michael C.; Bickert, Peter; Hafner, Klaus; Boekelheide, V.

1984-01-01

103

Scalar interactions between parallel jets measured using a two-channel PLIF technique  

NASA Astrophysics Data System (ADS)

A two-channel PLIF technique that simultaneously quantifies two scalar fields is presented. The technique consists of two independently operated single-color PLIF systems that synchronously image a common region. Two dyes (fluorescein sodium salt and oxazine 725) are excited by two lasers (argon-ion and krypton-ion), and the resulting fluorescence is imaged by a pair of cameras. The two-channel system is used to study mixing between two parallel jets, each transporting a different scalar species. Time-averaged and instantaneous mixing statistics are calculated and used to show the effects of turbulent structure on scalar mixing. In particular, the existence of positive spatial correlations between the two scalar fields is demonstrated in off-axis mixing regions.

Soltys, M. A.; Crimaldi, J. P.

2011-06-01

104

Plasma acceleration by the interaction of parallel propagating Alfv\\'en waves  

E-print Network

It is shown that two circularly polarised Alfv\\'en waves that propagate along the ambient magnetic field in an uniform plasma trigger non oscillating electromagnetic field components when they cross each other. The non-oscilliating field components can accelerate ions and electrons with great efficiency. This work is based on particle-in-cell (PIC) numerical simulations and on analytical non-linear computations. The analytical computations are done for two counter-propagating monochromatic waves. The simulations are done with monochromatic waves and with wave packets. The simulations show parallel electromagnetic fields consistent with the theory, and they show that the particle acceleration result in plasma cavities and, if the waves amplitudes are high enough, in ion beams. These acceleration processes could be relevant in space plasmas. For instance, they could be at work in the auroral zone and in the radiation belts of the Earth magnetosphere. In particular, they may explain the origin of the deep plasma...

Mottez, Fabrice

2014-01-01

105

Guided Analysis of Hurricane Trends Using Statistical Processes Integrated with Interactive Parallel Coordinates  

E-print Network

Guided Analysis of Hurricane Trends Using Statistical Processes Integrated with Interactive. The system's utility is demonstrated with an extensive hurricane climate study that was conducted by a hurricane expert. In the study, the expert used a new data set of environmental weather data, composed of 28

Swan II, J. Edward

106

Massively parallel measurements of molecular interaction kinetics on a microfluidic platform  

E-print Network

interactions with equilibrium dissociation constants ranging from 2 Ã? 10-6 M to 2 Ã? 10-9 M, and dissociation device. Overall, we obtained 2,388 association and dissociation curves of 223 unique molecular rate constants of approximately 6 s-1 to 8.5 Ã? 10-3 s-1. Association rate constants were uniform across

Halazonetis, Thanos

107

A parallel 3D computational method for uidstructure interactions in parachute systems  

E-print Network

canopy was represented as a structure with prescribed shape changes, and its dynamics was determined developing. Parachute systems present very complex dynamics arising from interactions between the canopy, sus- pension lines, payload, and the surrounding air. Parachutes can experience signi®cant canopy deformations

Tezduyar, Tayfun E.

108

DC Circuits: Parallel Resistances  

NSDL National Science Digital Library

In this interactive learning activity, students will learn about parallel circuits. They will measure and calculate the resistance of parallel circuits and answer several questions about the example circuit shown.

2013-07-30

109

DNS of hydrodynamically interacting droplets in turbulent clouds: Parallel implementation and scalability analysis using 2D domain decomposition  

NASA Astrophysics Data System (ADS)

The study of turbulent collision of cloud droplets requires simultaneous considerations of the transport by background air turbulence (i.e., geometric collision rate) and influence of droplet disturbance flows (i.e., collision efficiency). In recent years, this multiscale problem has been addressed through a hybrid direct numerical simulation (HDNS) approach (Ayala et al., 2007). This approach, while currently is the only viable tool to quantify the effects of air turbulence on collision statistics, is computationally expensive. In order to extend the HDNS approach to higher flow Reynolds numbers, here we developed a highly scalable implementation of the approach using 2D domain decomposition. The scalability of the parallel implementation was studied using several parallel computers, at 5123 and 10243 grid resolutions with O(106)-O(107) droplets. It was found that the execution time scaled with number of processors almost linearly until it saturates and deteriorates due to communication latency issues. To better understand the scalability, we developed a complexity analysis by partitioning the execution tasks into computation, communication, and data copy. Using this complexity analysis, we were able to predict the scalability performance of our parallel code. Furthermore, the theory was used to estimate the maximum number of processors below which the approximately linear scalability is sustained. We theoretically showed that we could efficiently solved problems of up to 81923 with O(100,000) processors. The complexity analysis revealed that the pseudo-spectral simulation of background turbulent flow for a dilute droplet suspension typical of cloud conditions typically takes about 80% of the total execution time, except when the droplets are small (less than 5 ?m in a flow with energy dissipation rate of 400 cm2/s3 and liquid water content of 1 g/m3), for which case the particle-particle hydrodynamic interactions become the bottleneck. The complexity analysis was also used to explore some alternative methods to handle FFT calculations within the flow simulation and to advance droplets less than 5 ?m in radius, for better computational efficiency. Finally, preliminary results are reported to shed light on the Reynolds number-dependence of collision kernel of non-interacting droplets.

Ayala, Orlando; Parishani, Hossein; Chen, Liu; Rosa, Bogdan; Wang, Lian-Ping

2014-12-01

110

Aeroacoustic interaction of a distributed vortex with a lifting Joukowski airfoil  

NASA Technical Reports Server (NTRS)

A first principles computational aeroacoustics calculation of the flow and noise fields produced by the interaction of a distributed vortex with a lifting Joukowski airfoil is accomplished at the Reynolds number of 200. The case considered is that where the circulations of the vortex and the airfoil are of opposite sign, corresponding to blade vortex interaction on the retreating side of a single helicopter rotor. The results show that the flow is unsteady, even in the absence of the incoming vortex, resulting in trailing edge noise generation. After the vortex is input, it initially experiences a quite rapid apparent diffusion rate produced by stretching in the airfoil velocity gradients. Consideration of the effects of finite vortex size and viscosity causes the noise radiation during the encounter to be much less impulsive than predicted by previous analyses.

Hardin, J. C.; Lamkin, S. L.

1984-01-01

111

Computation of interactional aerodynamics for noise prediction of heavy lift rotorcraft  

NASA Astrophysics Data System (ADS)

Many computational tools are used when developing a modern helicopter. As the design space is narrowed, more accurate and time-intensive tools are brought to bear. These tools are used to determine the effect of a design decision on the performance, handling, stability and efficiency of the aircraft. One notable parameter left out of this process is acoustics. This is due in part to the difficulty in making useful acoustics calculations that reveal the differences between various design configurations. This thesis presents a new approach designed to bridge the gap in prediction capability between fast but low-fidelity Lagrangian particle methods, and slow but high-fidelity Eulerian computational fluid dynamics simulations. A multi-pronged approach is presented. First, a simple flow solver using well-understood and tested flow solution methodologies is developed specifically to handle bodies in arbitrary motion. To this basic flow solver two new technologies are added. The first is an Immersed Boundary technique designed to be tolerant of geometric degeneracies and low-resolution grids. This new technique allows easy inclusion of complex fuselage geometries at minimal computational cost, improving the ability of a solver to capture the complex interactional aerodynamic effects expected in modern rotorcraft design. The second new technique is an extension of a concept from flow visualization where the motion of tip vortices are tracked through the solution using massless particles convecting with the local flow. In this extension of that concept, the particles maintain knowledge of the expected and actual vortex strength. As a post-processing step, when the acoustic calculations are made, these particles are used to augment the loading noise calculation and reproduce the highly-impulsive character of blade-vortex interaction noise. In combination these new techniques yield a significant improvement to the state of the art in rotorcraft blade-vortex interaction noise prediction.

Hennes, Christopher C.

112

Parallel Atomistic Simulations  

SciTech Connect

Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.

HEFFELFINGER,GRANT S.

2000-01-18

113

An experimental investigation of the chopping of helicopter main rotor tip vortices by the tail rotor  

NASA Technical Reports Server (NTRS)

The chopping of helicopter main rotor tip vortices by the tail rotor was experimentally investigated. This is a problem of blade vortex interaction (BVI) at normal incidence where the vortex is generally parallel to the rotor axis. The experiment used a model rotor and an isolated vortex and was designed to isolate BVI noise from other types of rotor noise. Tip Mach number, radical BVI station, and free stream velocity were varied. Fluctuating blade pressures, farfield sound pressure level and directivity, velocity field of the incident vortex, and blade vortex interaction angles were measured. Blade vortex interaction was found to produce impulsive noise which radiates primarily ahead of the blade. For interaction away from the blade tip, the results demonstrate the dipole character of BVI radiation. For BVI close to the tip, three dimensional relief effect reduces the intensity of the interaction, despite larger BVI angle and higher local Mach number. Furthermore, in this case, the radiation patern is more complex due to diffraction at and pressure communication around the tip.

Ahmadi, A. R.

1984-01-01

114

The structure of the carboxyl terminus of striated alpha-tropomyosin in solution reveals an unusual parallel arrangement of interacting alpha-helices.  

PubMed

Coiled coils are well-known as oligomerization domains, but they are also important sites of protein-protein interactions. We determined the NMR solution structure and backbone (15)N relaxation rates of a disulfide cross-linked, two-chain, 37-residue polypeptide containing the 34 C-terminal residues of striated muscle alpha-tropomyosin, TM9a(251-284). The peptide binds to the N-terminal region of TM and to the tropomyosin-binding domain of the regulatory protein, troponin T. Comparison of the NMR solution structure of TM9a(251-284) with the X-ray structure of a related peptide [Li, Y., Mui, S., Brown, J. H., Strand, J., Reshetnikova, L., Tobacman, L. S., and Cohen, C. (2002) Proc. Natl. Acad. Sci. U.S.A. 99, 7378-7383] reveals significant differences. In solution, residues 253-269 (like most of the tropomyosin molecule) form a canonical coiled coil. Residues 270-279, however, are parallel, linear helices, novel for tropomyosin. The packing between the parallel helices results from unusual interface residues that are atypical for coiled coils. Y267 has poor packing at the coiled-coil interface and a lower R(2) relaxation rate than neighboring residues, suggesting there is conformational flexibility around this residue. The last five residues are nonhelical and flexible. The exposed surface presented by the parallel helices, and the flexibility around Y267 and the ends, may facilitate binding to troponin T and formation of complexes with the N-terminus of tropomyosin and actin. We propose that unusual packing and flexibility are general features of coiled-coil domains in proteins that are involved in intermolecular interactions. PMID:12534273

Greenfield, Norma J; Swapna, G V T; Huang, Yuanpeng; Palm, Thomas; Graboski, Sarah; Montelione, Gaetano T; Hitchcock-DeGregori, Sarah E

2003-01-28

115

Nonlinear fluid–structure interaction problem. Part II: space discretization, implementation aspects, nested parallelization and application examples  

Microsoft Academic Search

The main focus of the present article is the development of a general solution framework for coupled and\\/or interaction multi-physics\\u000a problems based upon re-using existing codes into software products. In particular, we discuss how to build this software tool\\u000a for the case of fluid–structure interaction problem, from finite element code FEAP for structural and finite volume code OpenFOAM for fluid

Christophe Kassiotis; Adnan Ibrahimbegovic; Rainer Niekamp; Hermann G. Matthies

2011-01-01

116

Stochastic gyroresonant electron acceleration in a low-beta plasma. I - Interaction with parallel transverse cold plasma waves  

NASA Technical Reports Server (NTRS)

The gyroresonance of electrons with parallel transverse cold plasma waves is considered, and the Fokker-Planck equation describing the evolution of the electron distribution function in the presence of a spectrum of turbulence is derived. A new resonance which produces a divergence in the Fokker-Planck coefficients is identified; it results when the electron is in gyroresonance with a wave that has a group velocity equal to the velocity of the electron along the magnetic field. Under the assumption of a power-law spectral density, the Fokker-Planck coefficients are calculated numerically, and their complicated momentum and pitch-angle dependence, as well as the influence of various approximations to the dispersion relation, gyroresonance condition, and spectral density are discussed. It is found that there is no resonance gap at any pitch angle as long as the full gyroresonance condition is used and waves propagating on both directions are present.

Steinacker, Juergen; Miller, James A.

1992-01-01

117

Parallel Algorithms  

NSDL National Science Digital Library

Content prepared for the Supercomputing 2002 session on "Using Clustering Technologies in the Classroom". Contains a series of exercises for teaching parallel computing concepts through kinesthetic activities.

Gray, Paul

118

Parallel Optimisation  

NSDL National Science Digital Library

An introduction to optimisation techniques that may improve parallel performance and scaling on HECToR. It assumes that the reader has some experience of parallel programming including basic MPI and OpenMP. Scaling is a measurement of the ability for a parallel code to use increasing numbers of cores efficiently. A scalable application is one that, when the number of processors is increased, performs better by a factor which justifies the additional resource employed. Making a parallel application scale to many thousands of processes requires not only careful attention to the communication, data and work distribution but also to the choice of the algorithms to use. Since the choice of algorithm is too broad a subject and very particular to application domain to include in this brief guide we concentrate on general good practices towards parallel optimisation on HECToR.

119

Quantitative metabolite profiling utilizing parallel column analysis for simultaneous reversed-phase and hydrophilic interaction liquid chromatography separations combined with tandem mass spectrometry.  

PubMed

In this work, a fully automated parallel LC column method was established in order to perform orthogonal hydrophilic interaction chromatography (HILIC) and reversed-phase (RPLC) chromatography within one analytical run for targeted quantitative mass spectrometric determination of metabolites from central carbon metabolism. In this way, the analytical throughput could be significantly improved compared to previously established dual separation work flows involving two separate analytical runs. Two sample aliquots were simultaneously injected onto a dual column setup columns using a ten-port valve, and parallel separations were carried out. Sub 2 ?m particle size stationary phases were employed for both separation methods. HILIC and RPLC eluents were combined post column followed by ESI-MS/MS detection. The orthogonal separations were optimized, aiming at an overall separation with 2 retention time segments, while reversed-phase separation was accomplished within 5.5 min; metabolites on the HILIC phase were retained for a minimum time of 6 min. The overall run time was 15 min. The setup was applied to the quantification of 30 primary intercellular metabolites, including amino acids, organic acids, and nucleotides employing internal standardization by a fully (13)C-labeled yeast extract. The comparison with HILIC-MS/MS and RPLC-MS/MS in separate analytical runs revealed that an excellent analytical performance was achieved by the parallel LC column method. The experimental repeatability (N = 5) was on average <5% (only for 2 compounds >5%). Moreover, limits of detection for the new approach ranging from 0.002-15 ?M were in a good agreement with ones obtained in separate HILIC-MS/MS and RPLC-MS/MS runs (ranging from 0.01-44 ?M). PMID:24678888

Klavins, Kristaps; Drexler, Hedda; Hann, Stephan; Koellensperger, Gunda

2014-05-01

120

A non-periodic 2D semi-Lagrangian Vlasov code for laser–plasma interaction on parallel computer  

Microsoft Academic Search

For the first time, a 2D electromagnetic and relativistic semi-Lagrangian Vlasov model for a multi-computer environment was developed to study the laser–plasma interaction in an open system. Numerical simulations are presented for situations relevant to the penetration of an ultra-intense laser pulse inside a moderately overdense plasma and the relativistic filamentation instability in the case of an underdense plasma. The

A. Ghizzo; F. Huot; P. Bertrand

2003-01-01

121

Interactive Visualization of Large-Scale Hydrological Data using Emerging Technologies in Web Systems and Parallel Programming  

NASA Astrophysics Data System (ADS)

As geoscientists are confronted with increasingly massive datasets from environmental observations to simulations, one of the biggest challenges is having the right tools to gain scientific insight from the data and communicate the understanding to stakeholders. Recent developments in web technologies make it easy to manage, visualize and share large data sets with general public. Novel visualization techniques and dynamic user interfaces allow users to interact with data, and modify the parameters to create custom views of the data to gain insight from simulations and environmental observations. This requires developing new data models and intelligent knowledge discovery techniques to explore and extract information from complex computational simulations or large data repositories. Scientific visualization will be an increasingly important component to build comprehensive environmental information platforms. This presentation provides an overview of the trends and challenges in the field of scientific visualization, and demonstrates information visualization and communication tools developed within the light of these challenges.

Demir, I.; Krajewski, W. F.

2013-12-01

122

Parallel biocomputing  

PubMed Central

Background With the advent of high throughput genomics and high-resolution imaging techniques, there is a growing necessity in biology and medicine for parallel computing, and with the low cost of computing, it is now cost-effective for even small labs or individuals to build their own personal computation cluster. Methods Here we briefly describe how to use commodity hardware to build a low-cost, high-performance compute cluster, and provide an in-depth example and sample code for parallel execution of R jobs using MOSIX, a mature extension of the Linux kernel for parallel computing. A similar process can be used with other cluster platform software. Results As a statistical genetics example, we use our cluster to run a simulated eQTL experiment. Because eQTL is computationally intensive, and is conceptually easy to parallelize, like many statistics/genetics applications, parallel execution with MOSIX gives a linear speedup in analysis time with little additional effort. Conclusions We have used MOSIX to run a wide variety of software programs in parallel with good results. The limitations and benefits of using MOSIX are discussed and compared to other platforms. PMID:21418580

2011-01-01

123

DC Circuits: Series-Parallel Resistances  

NSDL National Science Digital Library

In this interactive learning activity, students will learn more about series-parallel circuits. They will measure and calculate the resistance of series-parallel circuits and answer several questions about the example circuit shown.

2013-07-29

124

Substituent-Modulated Affinities of Halobenzene Derivatives to the HIV-1 Integrase Recognition Site. Analyses of the Interaction Energies by Parallel Quantum Chemical and Polarizable Molecular Mechanics.  

PubMed

The C-X bond of halobenzenes (X = Cl, Br) has a dual character, its electron density being depleted in its prolongation and built-up on its sides. We have recently considered three protein or nucleic acid recognition sites of halobenzenes and quantified the energy gains that either electron-attracting substituents or electron-donating ones contribute due to such a character (El Hage et al., paper in revision). Nonadditivity was found to impact the total interaction energies. We focus here on one recognition site, that of the HIV-1 integrase, in which the halobenzene ring of the drug elvitegravir is sandwiched between a guanine and a cytosine base. We perform energy-decomposition analyses of the ab initio quantum-chemistry (QC) binding energies of the parent halobenzene ring and its derivatives with this G-C base pair. In these complexes, the nonadditivity of ?E could be traced back mostly to the polarization contribution Epol. In view of large-scale applications to the entirety of the complex formed between the integrase, the viral DNA, and the whole drug, the analyses were performed in parallel with a polarizable molecular mechanics method, SIBFA. This method could faithfully reproduce most features of the QC energies. This is due to its use of QC-derived distributed multipoles and polarizabilities, which enable us to account for both nonisotropy and nonadditivity. PMID:25230384

El Hage, Krystel; Piquemal, Jean-Philip; Hobaika, Zeina; Maroun, Richard G; Gresh, Nohad

2014-10-16

125

RecQL5 Promotes Genome Stabilization through Two Parallel Mechanisms—Interacting with RNA Polymerase II and Acting as a Helicase? †  

PubMed Central

The RecQL5 helicase is essential for maintaining genome stability and reducing cancer risk. To elucidate its mechanism of action, we purified a RecQL5-associated complex and identified its major component as RNA polymerase II (Pol II). Bioinformatics and structural modeling-guided mutagenesis revealed two conserved regions in RecQL5 as KIX and SRI domains, already known in transcriptional regulators for Pol II. The RecQL5-KIX domain binds both initiation (Pol IIa) and elongation (Pol IIo) forms of the polymerase, whereas the RecQL5-SRI domain interacts only with the elongation form. Fully functional RecQL5 requires both helicase activity and associations with the initiation polymerase, because mutants lacking either activity are partially defective in the suppression of sister chromatid exchange and resistance to camptothecin-induced DNA damage, and mutants lacking both activities are completely defective. We propose that RecQL5 promotes genome stabilization through two parallel mechanisms: by participation in homologous recombination-dependent DNA repair as a RecQ helicase and by regulating the initiation of Pol II to reduce transcription-associated replication impairment and recombination. PMID:20231364

Islam, M. Nurul; Fox, David; Guo, Rong; Enomoto, Takemi; Wang, Weidong

2010-01-01

126

Parallel MATLAB: Parallel For Loops  

E-print Network

.......... FSU: Florida State University AOE: Department of Aerospace and Ocean Engineering ARC: Advanced Research Computing ICAM: Interdisciplinary Center for Applied Mathematics 1 / 69 #12;MATLAB Parallel are completely independent; there are also some restrictions on array-data access. OpenMP implements a directive

Crawford, T. Daniel

127

Research investigation of helicopter main rotor/tail rotor interaction noise  

NASA Technical Reports Server (NTRS)

Acoustic measurements were obtained in a Langley 14 x 22 foot Subsonic Wind Tunnel to study the aeroacoustic interaction of 1/5th scale main rotor, tail rotor, and fuselage models. An extensive aeroacoustic data base was acquired for main rotor, tail rotor, fuselage aerodynamic interaction for moderate forward speed flight conditions. The details of the rotor models, experimental design and procedure, aerodynamic and acoustic data acquisition and reduction are presented. The model was initially operated in trim for selected fuselage angle of attack, main rotor tip-path-plane angle, and main rotor thrust combinations. The effects of repositioning the tail rotor in the main rotor wake and the corresponding tail rotor countertorque requirements were determined. Each rotor was subsequently tested in isolation at the thrust and angle of attack combinations for trim. The acoustic data indicated that the noise was primarily dominated by the main rotor, especially for moderate speed main rotor blade-vortex interaction conditions. The tail rotor noise increased when the main rotor was removed indicating that tail rotor inflow was improved with the main rotor present.

Fitzgerald, J.; Kohlhepp, F.

1988-01-01

128

Development of a prototype PET scanner with depth-of-interaction measurement using solid-state photomultiplier arrays and parallel readout electronics  

NASA Astrophysics Data System (ADS)

In this study, we developed a prototype animal PET by applying several novel technologies to use solid-state photomultiplier (SSPM) arrays to measure the depth of interaction (DOI) and improve imaging performance. Each PET detector has an 8 × 8 array of about 1.9 × 1.9 × 30.0 mm3 lutetium-yttrium-oxyorthosilicate scintillators, with each end optically connected to an SSPM array (16 channels in a 4 × 4 matrix) through a light guide to enable continuous DOI measurement. Each SSPM has an active area of about 3 × 3 mm2, and its output is read by a custom-developed application-specific integrated circuit to directly convert analogue signals to digital timing pulses that encode the interaction information. These pulses are transferred to and are decoded by a field-programmable gate array-based time-to-digital convertor for coincident event selection and data acquisition. The independent readout of each SSPM and the parallel signal process can significantly improve the signal-to-noise ratio and enable the use of flexible algorithms for different data processes. The prototype PET consists of two rotating detector panels on a portable gantry with four detectors in each panel to provide 16 mm axial and variable transaxial field-of-view (FOV) sizes. List-mode ordered subset expectation maximization image reconstruction was implemented. The measured mean energy, coincidence timing and DOI resolution for a crystal were about 17.6%, 2.8 ns and 5.6 mm, respectively. The measured transaxial resolutions at the center of the FOV were 2.0 mm and 2.3 mm for images reconstructed with and without DOI, respectively. In addition, the resolutions across the FOV with DOI were substantially better than those without DOI. The quality of PET images of both a hot-rod phantom and mouse acquired with DOI was much higher than that of images obtained without DOI. This study demonstrates that SSPM arrays and advanced readout/processing electronics can be used to develop a practical DOI-measureable PET scanner.

Shao, Yiping; Sun, Xishan; Lan, Kejian A.; Bircher, Chad; Lou, Kai; Deng, Zhi

2014-03-01

129

Parallel Computing Explained  

NSDL National Science Digital Library

Several tutorials on parallel computing. Overview of parallel computing. Porting and code parallelization. Scalar, cache, and parallel code tuning. Timing, profiling and performance analysis. Overview of IBM Regatta P690.

Ncsa

130

Scaling properties of geometric parallelization  

NASA Astrophysics Data System (ADS)

We present a universal scaling law for all geometrically parallelized computer simulation algorithms. For algorithms with local interaction laws we calculate the scaling exponents for zero and infinite lattice size. The scaling is tested on local (cellular automata, Metropolis Ising) as well as cluster (Swendsen-Wang) algorithms. The practical aspects of the scaling properties lead to a simple recipe for finding the optimum number of processors to be used for the parallel simulation of a particular system.

Jakobs, A.; Gerling, R. W.

1992-01-01

131

Serial Order: A Parallel Distributed Processing Approach.  

ERIC Educational Resources Information Center

Human behavior shows a variety of serially ordered action sequences. This paper presents a theory of serial order which describes how sequences of actions might be learned and performed. In this theory, parallel interactions across time (coarticulation) and parallel interactions across space (dual-task interference) are viewed as two aspects of a…

Jordan, Michael I.

132

Aerodynamic Requirements for BVI Noise Control  

NASA Technical Reports Server (NTRS)

As a rotor blade moves through the air, it sheds vortices. These vortices shed along the length of the blade over time form the wake. The strongest vortices of the wake are those trailing from the tip of the blade. When a rotating blade system moves under certain operating conditions, each blade will impinge on the tip vortices shed by itself or other blades. This impingement is called a blade-vortex interaction, or BVI. Although the blade and trailing tip vortices interact with many different orientations, one of the two extremes, either parallel or perpendicular interaction, is usually modelled. In a perpendicular interaction, the portion of the blade that is actually interacting with the travelling vortex at any given time is very small. A parallel interaction, however, has the largest concurrent interaction with the blade, as a result this case is given the most attention. One of the most commonly studied occurrences of blade-vortex interactions is associated with low-speed descending rotorcraft flight. BVI occur when the tip vortices shed by the blades intersect the plane of the rotor. BVI cause local pressure changes over the blades which are responsible, in part, for the acoustic signature of the rotorcraft. The local pressure changes also cause vibrations which lead to fatigue of both the blades and the mechanical components driving the blades.

Wells, Valana L.

1996-01-01

133

Speculative parallelization of partially parallel loops  

E-print Network

with even one cross- processor flow dependence because we have to re-execute sequentially. Moreover, the existing, partial parallelism of loops is not exploited. We demonstrate a generalization of the speculative doall parallelization tech- nique, called...

Dang, Francis Hoai Dinh

2009-05-15

134

Special parallel processing workshop  

SciTech Connect

This report contains viewgraphs from the Special Parallel Processing Workshop. These viewgraphs deal with topics such as parallel processing performance, message passing, queue structure, and other basic concept detailing with parallel processing.

NONE

1994-12-01

135

Coherent parallel C  

Microsoft Academic Search

Coherent Parallel C (CPC) is an extension of C for parallelism. The extensions are not simply parallel for loops; instead, a data parallel programming model is adopted. This means that one has an entire process for each data object. An example of an “object” is one mesh point in a finite element solver. How the processes are actually distributed on

Edward W. Felten; Steve W. Otto

1988-01-01

136

Computer-Aided Parallelizer and Optimizer  

NASA Technical Reports Server (NTRS)

The Computer-Aided Parallelizer and Optimizer (CAPO) automates the insertion of compiler directives (see figure) to facilitate parallel processing on Shared Memory Parallel (SMP) machines. While CAPO currently is integrated seamlessly into CAPTools (developed at the University of Greenwich, now marketed as ParaWise), CAPO was independently developed at Ames Research Center as one of the components for the Legacy Code Modernization (LCM) project. The current version takes serial FORTRAN programs, performs interprocedural data dependence analysis, and generates OpenMP directives. Due to the widely supported OpenMP standard, the generated OpenMP codes have the potential to run on a wide range of SMP machines. CAPO relies on accurate interprocedural data dependence information currently provided by CAPTools. Compiler directives are generated through identification of parallel loops in the outermost level, construction of parallel regions around parallel loops and optimization of parallel regions, and insertion of directives with automatic identification of private, reduction, induction, and shared variables. Attempts also have been made to identify potential pipeline parallelism (implemented with point-to-point synchronization). Although directives are generated automatically, user interaction with the tool is still important for producing good parallel codes. A comprehensive graphical user interface is included for users to interact with the parallelization process.

Jin, Haoqiang

2011-01-01

137

Parallel Mandelbrot Set Model  

NSDL National Science Digital Library

The Parallel Mandelbrot Set Model is a parallelization of the sequential MandelbrotSet model, which does all the computations on a single processor core. This parallelization is able to use a computer with more than one cores (or processors) to carry out the same computation, thus speeding up the process. The parallelization is done using the model elements in the Parallel Java group. These model elements allow easy use of the Parallel Java library created by Alan Kaminsky. In particular, the parallelization used for this model is based on code in Chapters 11 and 12 of Kaminsky's book Building Parallel Java. The Parallel Mandelbrot Set Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double click the ejs_chaos_ParallelMandelbrotSet.jar file to run the program if Java is installed.

Franciscouembre

2011-11-24

138

Virtual Reality and Parallel Systems Performance Analysis  

Microsoft Academic Search

Recording and analyzing the dynamics of application program, system software, and hardware interactions are the keys to understanding and tuning the performance of massively parallel systems. Because massively parallel systems contain hundreds or thousands of processors, each potentially with many dynamic performance metrics, the performance data occupy a sparsely populated, high-dimensional space. These dynamic performance metrics for each processor define

Daniel A. Reed; Keith A. Shields; Will H. Scullin; Luis F. Tawera; Christopher L. Elford

1995-01-01

139

Applied Parallel Metadata Indexing  

SciTech Connect

The GPFS Archive is parallel archive is a parallel archive used by hundreds of users in the Turquoise collaboration network. It houses 4+ petabytes of data in more than 170 million files. Currently, users must navigate the file system to retrieve their data, requiring them to remember file paths and names. A better solution might allow users to tag data with meaningful labels and searach the archive using standard and user-defined metadata, while maintaining security. last summer, I developed the backend to a tool that adheres to these design goals. The backend works by importing GPFS metadata into a MongoDB cluster, which is then indexed on each attribute. This summer, the author implemented security and developed the user interfae for the search tool. To meet security requirements, each database table is associated with a single user, which only stores records that the user may read, and requires a set of credentials to access. The interface to the search tool is implemented using FUSE (Filesystem in USErspace). FUSE is an intermediate layer that intercepts file system calls and allows the developer to redefine how those calls behave. In the case of this tool, FUSE interfaces with MongoDB to issue queries and populate output. A FUSE implementation is desirable because it allows users to interact with the search tool using commands they are already familiar with. These security and interface additions are essential for a usable product.

Jacobi, Michael R [Los Alamos National Laboratory

2012-08-01

140

TOPC: Mature Parallel Computing Gene Cooperman  

E-print Network

on Symbolic and Algebraic Computation (ISSAC '96), ACM Press, 155--160. #12; Life Cycle of A Task MASTER SLAVE. [6] G. Cooperman, ``STAR/MPI: Binding a Parallel Library to Interactive Symbolic Algebra Systems

Cooperman, Gene

141

Parallel computations and control of adaptive structures  

NASA Technical Reports Server (NTRS)

The equations of motion for structures with adaptive elements for vibration control are presented for parallel computations to be used as a software package for real-time control of flexible space structures. A brief introduction of the state-of-the-art parallel computational capability is also presented. Time marching strategies are developed for an effective use of massive parallel mapping, partitioning, and the necessary arithmetic operations. An example is offered for the simulation of control-structure interaction on a parallel computer and the impact of the approach presented for applications in other disciplines than aerospace industry is assessed.

Park, K. C.; Alvin, Kenneth F.; Belvin, W. Keith; Chong, K. P. (editor); Liu, S. C. (editor); Li, J. C. (editor)

1991-01-01

142

Compiling for NUMA Parallel Machines  

E-print Network

Compiling for NUMA Parallel Machines Abstract A common feature of many scalable parallel machines is non-uniform memory access (NUMA). A parallelizing compiler for NUMA parallel ma- chines must exploit both parallelism and data locality

Zanibbi, Richard

143

A Fast Parallel Simulation Code for Interaction between Proto-Planetary Disk and Embedded Proto-Planets: Implementation for 3D Code  

Microsoft Academic Search

We develop a 3D simulation code for interaction between the proto-planetary disk and embedded proto-planets. The protoplanetary disk is treated as a three-dimensional (3D), self-gravitating gas whose motion is described by the locally isothermal Navier-Stokes equations in a spherical coordinate centered on the star. The differential equations for the disk are similar to those given in Kley et al. (2009)

Shengtai Li; Hui Li

2012-01-01

144

Interaction  

NSDL National Science Digital Library

Set values for the initial position, velocity, and mass of the two particles, and click on the button "Initialize Animation" to play the animation using your specified values. Note, if m or v are too large, the particles may actually pass through one another which will seem a little strange. Note: the interaction between the particles is a "non-contact" interaction, much like the electrostatic force on two charges. Mathematically, it is actually a Hooke's law interaction.

Christian, Wolfgang; Belloni, Mario

2008-02-19

145

Parallel text search methods  

Microsoft Academic Search

A comparison of recently proposed parallel text search methods to alternative available search strategies that use serial processing machines suggests parallel methods do not provide large-scale gains in either retrieval effectiveness or efficiency.

Gerard Salton; Chris Buckley

1988-01-01

146

Parallel flow diffusion battery  

DOEpatents

A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

Yeh, Hsu-Chi (Albuquerque, NM); Cheng, Yung-Sung (Albuquerque, NM)

1984-08-07

147

Parallel flow diffusion battery  

DOEpatents

A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

Yeh, H.C.; Cheng, Y.S.

1984-01-01

148

The ParaScope parallel programming environment  

NASA Technical Reports Server (NTRS)

The ParaScope parallel programming environment, developed to support scientific programming of shared-memory multiprocessors, includes a collection of tools that use global program analysis to help users develop and debug parallel programs. This paper focuses on ParaScope's compilation system, its parallel program editor, and its parallel debugging system. The compilation system extends the traditional single-procedure compiler by providing a mechanism for managing the compilation of complete programs. Thus, ParaScope can support both traditional single-procedure optimization and optimization across procedure boundaries. The ParaScope editor brings both compiler analysis and user expertise to bear on program parallelization. It assists the knowledgeable user by displaying and managing analysis and by providing a variety of interactive program transformations that are effective in exposing parallelism. The debugging system detects and reports timing-dependent errors, called data races, in execution of parallel programs. The system combines static analysis, program instrumentation, and run-time reporting to provide a mechanical system for isolating errors in parallel program executions. Finally, we describe a new project to extend ParaScope to support programming in FORTRAN D, a machine-independent parallel programming language intended for use with both distributed-memory and shared-memory parallel computers.

Cooper, Keith D.; Hall, Mary W.; Hood, Robert T.; Kennedy, Ken; Mckinley, Kathryn S.; Mellor-Crummey, John M.; Torczon, Linda; Warren, Scott K.

1993-01-01

149

Verbal and Visual Parallelism  

ERIC Educational Resources Information Center

This study investigates the practice of presenting multiple supporting examples in parallel form. The elements of parallelism and its use in argument were first illustrated by Aristotle. Although real texts may depart from the ideal form for presenting multiple examples, rhetorical theory offers a rationale for minimal, parallel presentation. The…

Fahnestock, Jeanne

2003-01-01

150

Parallel simulation today  

NASA Technical Reports Server (NTRS)

This paper surveys topics that presently define the state of the art in parallel simulation. Included in the tutorial are discussions on new protocols, mathematical performance analysis, time parallelism, hardware support for parallel simulation, load balancing algorithms, and dynamic memory management for optimistic synchronization.

Nicol, David; Fujimoto, Richard

1992-01-01

151

Special issue on parallelism  

Microsoft Academic Search

The articles presented in our Special Issue on parallel processing on the supercomputing scale reflect, to some extent, splits in the community developing these machines. There are several schools of thought on how best to implement parallel processing at both the hard- and software levels. Controversy exists over the wisdom of aiming for general- or special-purpose parallel machines, and what

Karen A. Frenkel

1986-01-01

152

DYNAMIC LANGUAGE PARALLELIZATION  

E-print Network

DYNAMIC LANGUAGE PARALLELIZATION By Lorenz F. Huelsbergen A thesis submitted in partial fulfillment { MADISON 1993 #12;c Copyright 1993 by Lorenz F. Huelsbergen ii #12;DYNAMIC LANGUAGE PARALLELIZATION Lorenz F. Huelsbergen, Ph.D. University of Wisconsin{Madison 1993 Dynamic language parallelization is a new

Huelsbergen, Lorenz

153

Decomposing the Potentially Parallel  

NSDL National Science Digital Library

This course provides an introduction to the issues involved in decomposing problems onto parallel machines, and to the types of architectures and programming styles commonly found in parallel computers. The list of topics discussed includes types of decomposition, task farming, regular domain decomposition, unbalanced grids, and parallel molecular dynamics.

Elspeth Minty, Robert Davey, Alan Simpson, David Henty

154

Parallel algorithm development  

SciTech Connect

Rapid changes in parallel computing technology are causing significant changes in the strategies being used for parallel algorithm development. One approach is simply to write computer code in a standard language like FORTRAN 77 or with the expectation that the compiler will produce executable code that will run in parallel. The alternatives are: (1) to build explicit message passing directly into the source code; or (2) to write source code without explicit reference to message passing or parallelism, but use a general communications library to provide efficient parallel execution. Application of these strategies is illustrated with examples of codes currently under development.

Adams, T.F.

1996-06-01

155

Parallel digital forensics infrastructure.  

SciTech Connect

This report documents the architecture and implementation of a Parallel Digital Forensics infrastructure. This infrastructure is necessary for supporting the design, implementation, and testing of new classes of parallel digital forensics tools. Digital Forensics has become extremely difficult with data sets of one terabyte and larger. The only way to overcome the processing time of these large sets is to identify and develop new parallel algorithms for performing the analysis. To support algorithm research, a flexible base infrastructure is required. A candidate architecture for this base infrastructure was designed, instantiated, and tested by this project, in collaboration with New Mexico Tech. Previous infrastructures were not designed and built specifically for the development and testing of parallel algorithms. With the size of forensics data sets only expected to increase significantly, this type of infrastructure support is necessary for continued research in parallel digital forensics. This report documents the implementation of the parallel digital forensics (PDF) infrastructure architecture and implementation.

Liebrock, Lorie M. (New Mexico Tech, Socorro, NM); Duggan, David Patrick

2009-10-01

156

Languages for parallel architectures  

SciTech Connect

This book presents mathematical methods for modelling parallel computer architectures, based on the results of ESPRIT's project 415 on computer languages for parallel architectures. Presented are investigations incorporating a wide variety of programming styles, including functional,logic, and object-oriented paradigms. Topics cover include Philips's parallel object-oriented language POOL, lazy-functional languages, the languages IDEAL, K-LEAF, FP2, and Petri-net semantics for the AADL language.

Bakker, J.W.

1989-01-01

157

Optimistic parallelism requires abstractions  

Microsoft Academic Search

The problem of writing software for multicore processors is greatly simplified if we could automatically parallelize sequential programs. Although auto-parallelization has been studied for many decades, it has succeeded only in a few application areas such as dense matrix computations. In particular, auto-parallelization of irregular programs, which are organized around large, pointer-based data struc- tures like graphs, has seemed intractable.

Milind Kulkarni; Keshav Pingali; Bruce Walter; Ganesh Ramanarayanan; Kavita Bala; L. Paul Chew

2007-01-01

158

Complexity of parallel algorithms  

SciTech Connect

This thesis addresses a number of theoretical issues in parallel computation. There are many open questions relating to what can be done with parallel computers and what are the most effective techniques to use to develop parallel algorithms. The author examines various problems in hope of gaining insight to the general questions. One topic investigated is the relationship between sequential and parallel algorithms. Introduced is the concept of a P-complete algorithm to capture what it means for an algorithm to be inherently sequential . It is shown that a number of sequential greedy algorithms are P-complete, including the greedy algorithm for finding a path in a graph. However, a problem is not necessarily difficult if an algorithm to solve it is P-complete. In some cases, the natural sequential algorithm is P-complete but a different technique gives a fast parallel algorithm. This shows that it is necessary to use different techniques for parallel computation than are used for sequential computation. Fast parallel algorithms for a number of simple graph theory problems are given. The algorithms illustrate a number of different techniques that are useful for parallel algorithms. The final topic that we address is parallel approximation of P-complete problems.

Anderson

1985-11-01

159

Complexity of parallel algorithms  

SciTech Connect

This thesis addresses a number of theoretical issues in parallel computation. There are many open questions relating to what can be done with parallel computers and what are the most effective techniques to use to develop parallel algorithms. Various problems are examined in hope of gaining insight to the general questions. One topic investigated is the relationship between sequential and parallel algorithms. The concept of a P-complete algorithm is introduced to capture what it means for an algorithm to be inherently sequential. It is shown that a number of sequential greedy algorithms are P-complete, including the greedy algorithm for finding a path in a graph. However, an algorithm being P-complete does not necessarily mean that the problem is difficult. In some cases, the natural sequential algorithm is P-complete but a different technique gives a fast parallel algorithm. This shows that it is necessary to use different techniques for parallel computation than are used for sequential computation. Fast parallel algorithms are given for a number of simple graph theory problems. The algorithms illustrate a number of different techniques that are useful for parallel algorithms. A number of results on approximating P-complete problems with parallel algorithms are given that are similar to results on approximating NP-complete problems with sequential algorithms.

Anderson, R.J.

1986-01-01

160

Parallel MATLAB at VT: Parallel For Loops  

E-print Network

.......... FSU: Florida State University AOE: Department of Aerospace and Ocean Engineering ARC: Advanced Research Computing ICAM: Interdisciplinary Center for Applied Mathematics 1 / 56 #12;Matlab Parallel on the order of execution. There are also restrictions on array-data access. OpenMP implements a directive

Crawford, T. Daniel

161

Parallel MATLAB at VT: Parallel For Loops  

E-print Network

.......... FSU: Florida State University AOE: Department of Aerospace and Ocean Engineering ARC: Advanced Research Computing ICAM: Interdisciplinary Center for Applied Mathematics 1 / 71 #12;MATLAB Parallel are completely independent; there are also some restrictions on array-data access. OpenMP implements a directive

Crawford, T. Daniel

162

Parallel MATLAB at VT: Parallel For Loops  

E-print Network

.......... FSU: Florida State University AOE: Department of Aerospace and Ocean Engineering ARC: Advanced Research Computing ICAM: Interdisciplinary Center for Applied Mathematics 1 / 72 #12;MATLAB Parallel independent; there are also some restrictions on array-data access. OpenMP implements a directive

Crawford, T. Daniel

163

Parallelizing and De-parallelizing Elimination Orders.  

National Technical Information Service (NTIS)

The order in which the variables of a linear system are processed determines the total amounts of fill and work to perform LU decomposition on the system. We identify a trade off between the amounts of fill and work for a given order and the parallelism i...

C. F. Bornstein

1998-01-01

164

The triad in the region of the lowest-frequency parallel fundamental band (v5=1?0) of CH3SiH3: Fermi-type interactions and giant torsional splittings  

NASA Astrophysics Data System (ADS)

The lowest frequency parallel fundamental band ?5 of CH3SiH3 near 700 cm-1 has been measured at a resolution of 0.004 cm-1 with Fourier transform spectroscopy to investigate vibration-torsion-rotation interactions in symmetric tops. The torsional splittings in the spectrum are increased from ˜0.005 cm-1 to ˜1 cm-1 by Fermi-type vibration-torsion interactions between the torsional stack (v6=0,1,2,…) in the ground vibrational state and the corresponding stack for v5=1. Resonant interactions were observed between the states (v5=1,v6=0) and (v5=0,v6=5) for the rotational series with (k=±1,?=?1), where ? labels the torsional sublevels. In this resonance, the two unperturbed states are near opposite limits for torsional motion: (v5=0,v6=5) involves nearly free rotation, while (v5=1,v6=0) involves small amplitude torsional oscillation. For the (k=±1,?=?1) rotational series, perturbation-allowed transitions in the high overtone (v6=5?0) were observed. Over 750 frequencies measured here have been analyzed together with more than 2500 measurements involved in the recent analysis of the lowest-lying degenerate fundamental band ?12 given by Moazzen-Ahmadi et al. [J. Mol. Spectrosc. 175, 54 (1996)]. A fit to within experimental error was achieved using 41 parameters, an increase of only 4 when the new band is added. The analysis shows that the inclusion of the Fermi-type interactions leads to a considerable simplification of the Hamiltonian for the ground vibrational state. For example, both the second and third terms (V0,6,V0,9) in the Fourier expansion of the hindering potential as well as the torsional flexing term (F0,m) vanish in the ground state. The changes in the leading terms in the torsional Hamiltonian have been quantitatively explained by a contact transformation. The large perturbations produced by the interaction matrix elements off-diagonal by 5 units in v6 have serious implications for vibrational relaxation in molecules undergoing internal rotation.

Schroderus, J.; Moazzen-Ahmadi, N.; Ozier, I.

2001-07-01

165

Mirror versus parallel bimanual reaching  

PubMed Central

Background In spite of their importance to everyday function, tasks that require both hands to work together such as lifting and carrying large objects have not been well studied and the full potential of how new technology might facilitate recovery remains unknown. Methods To help identify the best modes for self-teleoperated bimanual training, we used an advanced haptic/graphic environment to compare several modes of practice. In a 2-by-2 study, we compared mirror vs. parallel reaching movements, and also compared veridical display to one that transforms the right hand’s cursor to the opposite side, reducing the area that the visual system has to monitor. Twenty healthy, right-handed subjects (5 in each group) practiced 200 movements. We hypothesized that parallel reaching movements would be the best performing, and attending to one visual area would reduce the task difficulty. Results The two-way comparison revealed that mirror movement times took an average 1.24 s longer to complete than parallel. Surprisingly, subjects’ movement times moving to one target (attending to one visual area) also took an average of 1.66 s longer than subjects moving to two targets. For both hands, there was also a significant interaction effect, revealing the lowest errors for parallel movements moving to two targets (p?parallel movements with a veridical display (moving to two separate targets). These results point to the expected levels of challenge for these bimanual training modes, which could be used to advise therapy choices in self-neurorehabilitation. PMID:23837908

2013-01-01

166

Optimistic parallelism requires abstractions  

Microsoft Academic Search

Irregular applications, which manipulate large, pointer-based data structures like graphs, are difficult to parallelize manually. Automatic tools and techniques such as restructuring compilers and run-time speculative execution have failed to uncover much parallelism in these applications, in spite of a lot of effort by the research community. These difficulties have even led some researchers to wonder if there is any

Milind Kulkarni; Keshav Pingali; Bruce Walter; Ganesh Ramanarayanan; Kavita Bala; L. Paul Chew

2007-01-01

167

Parallelization of thermochemical nanolithography.  

PubMed

One of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. Here, we demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of conjugated polymer nanostructures and graphene-based nanoribbons. PMID:24337109

Carroll, Keith M; Lu, Xi; Kim, Suenne; Gao, Yang; Kim, Hoe-Joon; Somnath, Suhas; Polloni, Laura; Sordan, Roman; King, William P; Curtis, Jennifer E; Riedo, Elisa

2014-01-01

168

Parallel Programming Workshop  

NSDL National Science Digital Library

This is an online course for parallel programming. Topics include MPI basics, point-to-point communication, derived datatypes, virtual topologies, collective communication, parallel I/O, and performance analysis and profiling. Other languages will be discussed such as OpenMP and High Performance Fortran (HPF). A Computational Fluid Dynamics section includes flux functions, Riemann solver, Euler equations, and Navier-Stokes equations.

169

Parallel discrete event simulation  

Microsoft Academic Search

Parallel discrete event simulation (PDES), sometimes called distributed simulation, refers to the execution of a single discrete event simulation program on a parallel computer. PDES has attracted a considerable amount of interest in recent years. From a pragmatic standpoint, this interest arises from the fact that large simulations in engineering, computer science, economics, and military applications, to mention a few,

Richard M. Fujimoto

1990-01-01

170

Conscious Parallelism Revisited  

Microsoft Academic Search

Conscious parallelism, sometimes called tacit collusion, occurs where firms adopt their business practices based on what other firms are doing, rather than competing for customers. The most obvious manifestation occurs where prices across companies in an industry not only become suspiciously similar, but also change rapidly in strikingly parallel ways. Suggested examples are legion and varied: airline tickets, gasoline, cellular

Reza Dibadj

2010-01-01

171

Unique features of the anti-parallel, heterodimeric coiled-coil interaction between methyl-cytosine binding domain 2 (MBD2) homologues and GATA zinc finger domain containing 2A (GATAD2A/p66?).  

PubMed

The methyl-cytosine binding domain 2 (MBD2)-nucleosome remodeling and deacetylase (NuRD) complex recognizes methylated DNA and silences expression of associated genes through histone deacetylase and nucleosome remodeling functions. Our previous structural work demonstrated that a coiled-coil interaction between MBD2 and GATA zinc finger domain containing 2A (GATAD2A/p66?) proteins recruits the chromodomain helicase DNA-binding protein (CHD4/Mi2?) to the NuRD complex and is necessary for MBD2-mediated DNA methylation-dependent gene silencing in vivo (Gnanapragasam, M. N., Scarsdale, J. N., Amaya, M. L., Webb, H. D., Desai, M. A., Walavalkar, N. M., Wang, S. Z., Zu Zhu, S., Ginder, G. D., and Williams, D. C., Jr. (2011) p66?-MBD2 coiled-coil interaction and recruitment of Mi-2 are critical for globin gene silencing by the MBD2-NuRD complex. Proc. Natl. Acad. Sci. U.S.A. 108, 7487-7492). The p66?-MBD2 interaction differs from most coiled-coils studied to date by forming an anti-parallel heterodimeric complex between two peptides that are largely monomeric in isolation. To further characterize unique features of this complex that drive heterodimeric specificity and high affinity binding, we carried out biophysical analyses of MBD2 and the related homologues MBD3, MBD3-like protein 1 (MBD3L1), and MBD3-like protein 2 (MBD3L2) as well as specific mutations that modify charge-charge interactions and helical propensity of the coiled-coil domains. Analytical ultracentrifugation analyses show that the individual peptides remain monomeric in isolation even at 300 ?M in concentration for MBD2. Circular dichroism analyses demonstrate a direct correlation between helical content of the coiled-coil domains in isolation and binding affinity for p66?. Furthermore, complementary electrostatic surface potentials and inherent helical content of each peptide are necessary to maintain high-affinity association. These factors lead to a binding affinity hierarchy of p66? for the different MBD2 homologues (MBD2 ? MBD3 > MBD3L1 ? MBD3L2) and suggest a hierarchical regulatory model in tissue and life cycle stage-specific silencing by NuRD complexes. PMID:23239876

Walavalkar, Ninad M; Gordon, Nathaniel; Williams, David C

2013-02-01

172

A dual-site simultaneous binding mode in the interaction between parallel-stranded G-quadruplex [d(TGGGGT)]4 and cyanine dye 2,2?-diethyl-9-methyl-selenacarbocyanine bromide  

PubMed Central

G-quadruplexes have attracted growing attention as a potential cancer-associated target for both treatment and detection in recent years. For detection purpose, high specificity is one of the most important factors to be considered in G-quadruplex probe design. It is well known that end stacking and groove binding are two dominated quadruplex-ligand binding modes, and currently most reported G-quadruplex probes are designed based on the former, which has been proven to show good selectivity between quadruplexes and non-quadruplexes. Because groove of G-quadruplex also has some unique chemical properties, it could be inferred that probes that can interact with both the groove and G-tetrad site of certain G-quadruplexes simultaneously might possess higher specificity in aspects of discriminating different quadruplexes. In this article, we report a cyanine dye as a potential novel probe scaffold that could occupy both the 5?-end external G-tetrad and the corresponding groove of the G-quadruplex simultaneously. By using various spectrum and nuclear magnetic resonance techniques, we give a detailed binding characterization for this dual-site simultaneous binding mode. A preliminary result suggests that this mode might provide highly specific recognition to a parallel-stranded G-quadruplex. These findings and the structural elucidation might give some clues in aspects of developing highly specific G-quadruplex probes. PMID:23275573

Gai, Wei; Yang, Qianfan; Xiang, Junfeng; Jiang, Wei; Li, Qian; Sun, Hongxia; Guan, Aijiao; Shang, Qian; Zhang, Hong; Tang, Yalin

2013-01-01

173

Parallel Adaptive Mesh Refinement  

SciTech Connect

As large-scale, parallel computers have become more widely available and numerical models and algorithms have advanced, the range of physical phenomena that can be simulated has expanded dramatically. Many important science and engineering problems exhibit solutions with localized behavior where highly-detailed salient features or large gradients appear in certain regions which are separated by much larger regions where the solution is smooth. Examples include chemically-reacting flows with radiative heat transfer, high Reynolds number flows interacting with solid objects, and combustion problems where the flame front is essentially a two-dimensional sheet occupying a small part of a three-dimensional domain. Modeling such problems numerically requires approximating the governing partial differential equations on a discrete domain, or grid. Grid spacing is an important factor in determining the accuracy and cost of a computation. A fine grid may be needed to resolve key local features while a much coarser grid may suffice elsewhere. Employing a fine grid everywhere may be inefficient at best and, at worst, may make an adequately resolved simulation impractical. Moreover, the location and resolution of fine grid required for an accurate solution is a dynamic property of a problem's transient features and may not be known a priori. Adaptive mesh refinement (AMR) is a technique that can be used with both structured and unstructured meshes to adjust local grid spacing dynamically to capture solution features with an appropriate degree of resolution. Thus, computational resources can be focused where and when they are needed most to efficiently achieve an accurate solution without incurring the cost of a globally-fine grid. Figure 1.1 shows two example computations using AMR; on the left is a structured mesh calculation of a impulsively-sheared contact surface and on the right is the fuselage and volume discretization of an RAH-66 Comanche helicopter [35]. Note the ability of both meshing methods to resolve simulation details by varying the local grid spacing.

Diachin, L; Hornung, R; Plassmann, P; WIssink, A

2005-03-04

174

Parallel interacting edge cracks under pure bending  

E-print Network

of the singularity 1//r is, therefore, also demonstrated. Photoelastic means are used to achieve a video image of the distribution of shear stresses around the crack tip through a fringe pattern. The stress intensity factors, K, and K?, describe the stresses... at any point of the fringe pattern. The non-singular term c in the elastic equations assumes the value 0 in the case of pure bending. The results are compared to those achieved by other methods such as the boundary collocation or the fourth power...

Moran, Ivan

2012-06-07

175

Bilingual parallel programming  

SciTech Connect

Numerous experiments have demonstrated that computationally intensive algorithms support adequate parallelism to exploit the potential of large parallel machines. Yet successful parallel implementations of serious applications are rare. The limiting factor is clearly programming technology. None of the approaches to parallel programming that have been proposed to date -- whether parallelizing compilers, language extensions, or new concurrent languages -- seem to adequately address the central problems of portability, expressiveness, efficiency, and compatibility with existing software. In this paper, we advocate an alternative approach to parallel programming based on what we call bilingual programming. We present evidence that this approach provides and effective solution to parallel programming problems. The key idea in bilingual programming is to construct the upper levels of applications in a high-level language while coding selected low-level components in low-level languages. This approach permits the advantages of a high-level notation (expressiveness, elegance, conciseness) to be obtained without the cost in performance normally associated with high-level approaches. In addition, it provides a natural framework for reusing existing code.

Foster, I.; Overbeek, R.

1990-01-01

176

Code Parallelization with CAPO: A User Manual  

NASA Technical Reports Server (NTRS)

A software tool has been developed to assist the parallelization of scientific codes. This tool, CAPO, extends an existing parallelization toolkit, CAPTools developed at the University of Greenwich, to generate OpenMP parallel codes for shared memory architectures. This is an interactive toolkit to transform a serial Fortran application code to an equivalent parallel version of the software - in a small fraction of the time normally required for a manual parallelization. We first discuss the way in which loop types are categorized and how efficient OpenMP directives can be defined and inserted into the existing code using the in-depth interprocedural analysis. The use of the toolkit on a number of application codes ranging from benchmark to real-world application codes is presented. This will demonstrate the great potential of using the toolkit to quickly parallelize serial programs as well as the good performance achievable on a large number of toolkit to quickly parallelize serial programs as well as the good performance achievable on a large number of processors. The second part of the document gives references to the parameters and the graphic user interface implemented in the toolkit. Finally a set of tutorials is included for hands-on experiences with this toolkit.

Jin, Hao-Qiang; Frumkin, Michael; Yan, Jerry; Biegel, Bryan (Technical Monitor)

2001-01-01

177

Series/Parallel Batteries  

NSDL National Science Digital Library

It is important for students to understand how resistors, capacitors, and batteries combine in series and parallel. The combination of batteries has a lot of practical applications in science competitions. This lab also reinforces how to use a voltmeter t

Horton, Michael

2009-05-30

178

Parallel Plate Antenna.  

National Technical Information Service (NTIS)

The invention as disclosed is a parallel plate antenna having a number of stacked horizontal plates and two vertical plates. Alternating ones of the horizontal plates are electrically coupled to one vertical plate such that the horizontal plates coupled t...

D. F. Rivera

2009-01-01

179

Parallels with nature  

NASA Astrophysics Data System (ADS)

Adam Nelson and Stuart Warriner, from the University of Leeds, talk with Nature Chemistry about their work to develop viable synthetic strategies for preparing new chemical structures in parallel with the identification of desirable biological activity.

2014-10-01

180

Calculational parallel programming: parallel programming with homomorphism and mapreduce  

Microsoft Academic Search

Parallel skeletons are designed to encourage programmers to build parallel programs from ready-made components for which efficient implementations are known to exist, making both parallel programming and parallelization process simpler. Homomorphism and mapReduce are two known parallel skeletons. Homomorphism, widely studied in the program calculation community for more than twenty years, ideally suits the divide-and-conquer parallel computation paradigm over lists,

Zhenjiang Hu; K. Emoto; Z. Hu; K. Kakehi; K. Matsuzaki; M. Takeichi

2010-01-01

181

Scalable parallel communications  

NASA Technical Reports Server (NTRS)

Coarse-grain parallelism in networking (that is, the use of multiple protocol processors running replicated software sending over several physical channels) can be used to provide gigabit communications for a single application. Since parallel network performance is highly dependent on real issues such as hardware properties (e.g., memory speeds and cache hit rates), operating system overhead (e.g., interrupt handling), and protocol performance (e.g., effect of timeouts), we have performed detailed simulations studies of both a bus-based multiprocessor workstation node (based on the Sun Galaxy MP multiprocessor) and a distributed-memory parallel computer node (based on the Touchstone DELTA) to evaluate the behavior of coarse-grain parallelism. Our results indicate: (1) coarse-grain parallelism can deliver multiple 100 Mbps with currently available hardware platforms and existing networking protocols (such as Transmission Control Protocol/Internet Protocol (TCP/IP) and parallel Fiber Distributed Data Interface (FDDI) rings); (2) scale-up is near linear in n, the number of protocol processors, and channels (for small n and up to a few hundred Mbps); and (3) since these results are based on existing hardware without specialized devices (except perhaps for some simple modifications of the FDDI boards), this is a low cost solution to providing multiple 100 Mbps on current machines. In addition, from both the performance analysis and the properties of these architectures, we conclude: (1) multiple processors providing identical services and the use of space division multiplexing for the physical channels can provide better reliability than monolithic approaches (it also provides graceful degradation and low-cost load balancing); (2) coarse-grain parallelism supports running several transport protocols in parallel to provide different types of service (for example, one TCP handles small messages for many users, other TCP's running in parallel provide high bandwidth service to a single application); and (3) coarse grain parallelism will be able to incorporate many future improvements from related work (e.g., reduced data movement, fast TCP, fine-grain parallelism) also with near linear speed-ups.

Maly, K.; Khanna, S.; Overstreet, C. M.; Mukkamala, R.; Zubair, M.; Sekhar, Y. S.; Foudriat, E. C.

1992-01-01

182

Parallel image compression  

NASA Technical Reports Server (NTRS)

A parallel compression algorithm for the 16,384 processor MPP machine was developed. The serial version of the algorithm can be viewed as a combination of on-line dynamic lossless test compression techniques (which employ simple learning strategies) and vector quantization. These concepts are described. How these concepts are combined to form a new strategy for performing dynamic on-line lossy compression is discussed. Finally, the implementation of this algorithm in a massively parallel fashion on the MPP is discussed.

Reif, John H.

1987-01-01

183

Parallelization for geophysical waveform analysis  

E-print Network

&M University to aid the parallel programmer by providing standard implementations of common parallel programming tasks. Our research involves using STAPL to apply parallel methods to a problem that has already been solved sequentially: Seismic ray tracing...

Kurth, Derek Edward

2013-02-22

184

Aerodynamic, aeroacoustic, and aeroelastic investigations of airfoil-vortex interaction using large-eddy simulation  

NASA Astrophysics Data System (ADS)

In helicopters, vortices (generated at the tip of the rotor blades) interact with the next advancing blades during certain flight and manoeuvring conditions, generating undesirable levels of acoustic noise and vibration. These Blade-Vortex Interactions (BVIs), which may cause the most disturbing acoustic noise, normally occur in descent or high-speed forward flight. Acoustic noise characterization (and potential reduction) is one the areas generating intensive research interest to the rotorcraft industry. Since experimental investigations of BVI are extremely costly, some insights into the BVI or AVI (2-D Airfoil-Vortex Interaction) can be gained using Computational Fluid Dynamics (CFD) numerical simulations. Numerical simulation of BVI or AVI has been of interest to CFD for many years. There are still difficulties concerning an accurate numerical prediction of BVI. One of the main issues is the inherent dissipation of CFD turbulence models, which severely affects the preservation of the vortex characteristics. Moreover this is not an issue only for aerodynamic and aeroacoustic analysis but also for aeroelastic investigations as well, especially when the strong (two-way) aeroelastic coupling is of interest. The present investigation concentrates mainly on AVI simulations. The simulations are performed for Mach number, Ma = 0.3, resulting in a Reynolds number, Re = 1.3 x 106, which is based on the chord, c, of the airfoil (NACA0012). Extensive literature search has indicated that the present work represents the first comprehensive investigation of AVI using the LES numerical approach, in the rotorcraft research community. The major factor affecting the aerodynamic coefficients and aeroacoustic field as a result of airfoil-vortex interaction is observed to be the unsteady pressure generated at the location of the interaction. The present numerical results show that the aerodynamic coefficients (lift, moment, and drag) and aeroacoustic field are strongly dependent on the airfoil-vortex vertical miss-distance, airfoil angle of attack, vortex characteristics, and aeroelastic response of airfoil to airfoil-vortex interaction. A decay of airfoil-vortex interactions with the increase of vertical miss-distance and angle of attack was observed. Also, a decay of airfoil-vortex interactions is observed for the case of a flexible structure when compared with the case of a rigid structure. The decay of vortex core size produces a decrease in the aerodynamic coefficients.

Ilie, Marcel

185

Sublattice parallel replica dynamics.  

PubMed

Exascale computing presents a challenge for the scientific community as new algorithms must be developed to take full advantage of the new computing paradigm. Atomistic simulation methods that offer full fidelity to the underlying potential, i.e., molecular dynamics (MD) and parallel replica dynamics, fail to use the whole machine speedup, leaving a region in time and sample size space that is unattainable with current algorithms. In this paper, we present an extension of the parallel replica dynamics algorithm [A. F. Voter, Phys. Rev. B 57, R13985 (1998)] by combining it with the synchronous sublattice approach of Shim and Amar [ and , Phys. Rev. B 71, 125432 (2005)], thereby exploiting event locality to improve the algorithm scalability. This algorithm is based on a domain decomposition in which events happen independently in different regions in the sample. We develop an analytical expression for the speedup given by this sublattice parallel replica dynamics algorithm and compare it with parallel MD and traditional parallel replica dynamics. We demonstrate how this algorithm, which introduces a slight additional approximation of event locality, enables the study of physical systems unreachable with traditional methodologies and promises to better utilize the resources of current high performance and future exascale computers. PMID:25019913

Martínez, Enrique; Uberuaga, Blas P; Voter, Arthur F

2014-06-01

186

Sublattice parallel replica dynamics  

NASA Astrophysics Data System (ADS)

Exascale computing presents a challenge for the scientific community as new algorithms must be developed to take full advantage of the new computing paradigm. Atomistic simulation methods that offer full fidelity to the underlying potential, i.e., molecular dynamics (MD) and parallel replica dynamics, fail to use the whole machine speedup, leaving a region in time and sample size space that is unattainable with current algorithms. In this paper, we present an extension of the parallel replica dynamics algorithm [A. F. Voter, Phys. Rev. B 57, R13985 (1998), 10.1103/PhysRevB.57.R13985] by combining it with the synchronous sublattice approach of Shim and Amar [Y. Shim and J. G. Amar, Phys. Rev. B 71, 125432 (2005), 10.1103/PhysRevB.71.125432], thereby exploiting event locality to improve the algorithm scalability. This algorithm is based on a domain decomposition in which events happen independently in different regions in the sample. We develop an analytical expression for the speedup given by this sublattice parallel replica dynamics algorithm and compare it with parallel MD and traditional parallel replica dynamics. We demonstrate how this algorithm, which introduces a slight additional approximation of event locality, enables the study of physical systems unreachable with traditional methodologies and promises to better utilize the resources of current high performance and future exascale computers.

Martínez, Enrique; Uberuaga, Blas P.; Voter, Arthur F.

2014-06-01

187

Method of moment solutions to scattering problems in a parallel processing environment  

NASA Technical Reports Server (NTRS)

This paper describes the implementation of a parallelized method of moments (MOM) code into an interactive workstation environment. The workstation allows interactive solid body modeling and mesh generation, MOM analysis, and the graphical display of results. After describing the parallel computing environment, the implementation and results of parallelizing a general MOM code are presented in detail.

Cwik, Tom; Partee, Jonathan; Patterson, Jean

1991-01-01

188

Parallel FFT & Isoefficiency 1 The Fast Fourier Transform in Parallel  

E-print Network

Parallel FFT & Isoefficiency 1 The Fast Fourier Transform in Parallel the Fastest Fourier Transform / 25 #12;Parallel FFT & Isoefficiency 1 The Fast Fourier Transform in Parallel the Fastest Fourier & Isoefficiency L-14 14 February 2014 2 / 25 #12;the Discrete Fourier Transform (DFT) A periodic function f(t) can

Verschelde, Jan

189

Parallel simulated annealing algorithms for cell placement on hypercube multiprocessors  

NASA Technical Reports Server (NTRS)

Two parallel algorithms for standard cell placement using simulated annealing are developed to run on distributed-memory message-passing hypercube multiprocessors. The cells can be mapped in a two-dimensional area of a chip onto processors in an n-dimensional hypercube in two ways, such that both small and large cell exchange and displacement moves can be applied. The computation of the cost function in parallel among all the processors in the hypercube is described, along with a distributed data structure that needs to be stored in the hypercube to support the parallel cost evaluation. A novel tree broadcasting strategy is used extensively for updating cell locations in the parallel environment. A dynamic parallel annealing schedule estimates the errors due to interacting parallel moves and adapts the rate of synchronization automatically. Two novel approaches in controlling error in parallel algorithms are described: heuristic cell coloring and adaptive sequence control.

Banerjee, Prithviraj; Jones, Mark Howard; Sargent, Jeff S.

1990-01-01

190

New Computational Methods for the Prediction and Analysis of Helicopter Noise  

NASA Technical Reports Server (NTRS)

This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise.

Strawn, Roger C.; Oliker, Leonid; Biswas, Rupak

1996-01-01

191

Massively parallel processor  

NASA Technical Reports Server (NTRS)

A brief description is given of the Massively Parallel Processor (MPP). Major applications of the MPP are in the area of image processing (where the operands are often very small integers) from very high spatial resolution passive image sensors, signal processing of radar data, and numerical modeling simulations of climate. The system can be programmed in assembly language or a high level language. Information on background, status, architecture, programming, hardware reliability, applications, and the MPP's development as a national resource for parallel algorithm research are presented in outline form.

1985-01-01

192

Scalable Parallel Crash Simulations  

SciTech Connect

We are pleased to submit our efforts in parallelizing the PRONTO application suite for con- sideration in the SuParCup 99 competition. PRONTO is a finite element transient dynamics simulator which includes a smoothed particle hydrodynamics (SPH) capability; it is similar in scope to the well-known DYNA, PamCrash, and ABAQUS codes. Our efforts over the last few years have produced a fully parallel version of the entire PRONTO code which (1) runs fast and scalably on thousands of processors, (2) has performed the largest finite-element transient dynamics simulations we are aware of, and (3) includes several new parallel algorithmic ideas that have solved some difficult problems associated with contact detection and SPH scalability. We motivate this work, describe the novel algorithmic advances, give performance numbers for PRONTO running on Sandia's Intel Teraflop machine, and highlight two prototypical large-scale computations we have performed with the parallel code. We have successfully parallelized a large-scale production transient dynamics code with a novel algorithmic approach that utilizes multiple decompositions for different key segments of the computations. To be able to simulate a more than ten million element model in a few tenths of second per timestep is unprecedented for solid dynamics simulations, especially when full global contact searches are required. The key reason is our new algorithmic ideas for efficiently parallelizing the contact detection stage. To our knowledge scalability of this computation had never before been demonstrated on more than 64 processors. This has enabled parallel PRONTO to become the only solid dynamics code we are aware of that can run effectively on 1000s of processors. More importantly, our parallel performance compares very favorably to the original serial PRONTO code which is optimized for vector supercomputers. On the container crush problem, a Teraflop node is as fast as a single processor of the Cray Jedi. This means that on the Teraflop machine we can now run simulations with tens of millions of elements thousands of times faster than we could on the Jedi! This is enabling transient dynamics simulations of unprecedented scale and fidelity. Not only can previous applications be run with vastly improved resolution and speed, but qualitatively new and different analyses have been made possible.

Attaway, Stephen; Barragy, Ted; Brown, Kevin; Gardner, David; Gruda, Jeff; Heinstein, Martin; Hendrickson, Bruce; Metzinger, Kurt; Neilsen, Mike; Plimpton, Steve; Pott, John; Swegle, Jeff; Vaughan, Courtenay

1999-06-01

193

Declarative Parallel Programming for GPUs  

E-print Network

, Arun CHAUHAN,Andrew LUMSDAINE Indiana University, Bloomington, USA ParCo 2011 September 1, 2011 #12;Arun Chauhan, Declarative parallel programming for GPUs, ParCo 2011 Parallelism Mainstream Parallelism nets Focus of today's Parallel Programming Models Courtesy:Vivek Sarkar, Rice University #12;Arun

Chauhan, Arun

194

Parallel Seismic Ray Tracing  

E-print Network

of the method while others are intended to be representative of basic geological features such as salt domes. We also present a theoretical model to understand the performance of the pWFC algorithm. We evaluate the performance of the proposed parallel...

Jain, Tarun K

2013-12-09

195

Parallel programming with PCN  

SciTech Connect

PCN is a system for developing and executing parallel programs. It comprises a high-level programming language, tools for developing and debugging programs in this language, and interfaces to Fortran and Cthat allow the reuse of existing code in multilingual parallel programs. Programs developed using PCN are portable across many different workstations, networks, and parallel computers. This document provides all the information required to develop parallel programs with the PCN programming system. It includes both tutorial and reference material. It also presents the basic concepts that underlie PCN, particularly where these are likely to be unfamiliar to the reader, and provides pointers to other documentation on the PCN language, programming techniques, and tools. PCN is in the public domain. The latest version of both the software and this manual can be obtained by anonymous ftp from Argonne National Laboratory in the directory pub/pcn at info.mcs. ani.gov (cf. Appendix A). This version of this document describes PCN version 2.0, a major revision of the PCN programming system. It supersedes earlier versions of this report.

Foster, I.; Tuecke, S.

1993-01-01

196

High performance parallel architectures  

SciTech Connect

In this paper the author describes current high performance parallel computer architectures. A taxonomy is presented to show computer architecture from the user programmer's point-of-view. The effects of the taxonomy upon the programming model are described. Some current architectures are described with respect to the taxonomy. Finally, some predictions about future systems are presented. 5 refs., 1 fig.

Anderson, R.E. (Lawrence Livermore National Lab., CA (USA))

1989-09-01

197

Parallel Circuits Lab  

NSDL National Science Digital Library

This in-class lab exercise will give students a familiarity with basic series and parallel circuits as well as measuring voltage, current and resistance. The worksheet provided leads students through the experiment step by step. Spaces for student measurements and conclusions are provided on the sheet. This document may be downloaded in PDF file format.

2012-05-04

198

Optimizing parallel reduction operations  

SciTech Connect

A parallel program consists of sets of concurrent and sequential tasks. Often, a reduction (such as array sum) sequentially combines values produced by a parallel computation. Because reductions occur so frequently in otherwise parallel programs, they are good candidates for optimization. Since reductions may introduce dependencies, most languages separate computation and reduction. The Sisal functional language is unique in that reduction is a natural consequence of loop expressions; the parallelism is implicit in the language. Unfortunately, the original language supports only seven reduction operations. To generalize these expressions, the Sisal 90 definition adds user-defined reductions at the language level. Applicable optimizations depend upon the mathematical properties of the reduction. Compilation and execution speed, synchronization overhead, memory use and maximum size influence the final implementation. This paper (1) Defines reduction syntax and compares with traditional concurrent methods; (2) Defines classes of reduction operations; (3) Develops analysis of classes for optimized concurrency; (4) Incorporates reductions into Sisal 1.2 and Sisal 90; (5) Evaluates performance and size of the implementations.

Denton, S.M.

1995-06-01

199

Parallelizing MATLAB Arun Chauhan  

E-print Network

Parallelizing MATLAB Arun Chauhan Indiana University ParaM Supercomputing, OSC booth, 2004-11-10 #12;The Performance Gap ParaM, Arun Chauhan, Indiana University Supercomputing, OSC booth, 2004-11-10 #12;MATLAB Example function mcc demo x = 1; y = x / 10; z = x * 20; r = y + z; ParaM, Arun Chauhan

Chauhan, Arun

200

Parallel Consensual Neural Networks  

Microsoft Academic Search

Optimized combination, regularization, and pruning is proposed for the Parallel Consensual Neural Networks (PC- NNs) which is a neural network architecture based on the consensus of a collection of stage neural networks trained on the same input data with dieren t representations. Here, a regularization scheme is presented for the PCNN and in training a regularized cost function is minimized.

J. A. Benediktsson; J. Larsen; J. R. Sveinsson; L. K. Hansen

201

Massively parallel processor computer  

NASA Technical Reports Server (NTRS)

An apparatus for processing multidimensional data with strong spatial characteristics, such as raw image data, characterized by a large number of parallel data streams in an ordered array is described. It comprises a large number (e.g., 16,384 in a 128 x 128 array) of parallel processing elements operating simultaneously and independently on single bit slices of a corresponding array of incoming data streams under control of a single set of instructions. Each of the processing elements comprises a bidirectional data bus in communication with a register for storing single bit slices together with a random access memory unit and associated circuitry, including a binary counter/shift register device, for performing logical and arithmetical computations on the bit slices, and an I/O unit for interfacing the bidirectional data bus with the data stream source. The massively parallel processor architecture enables very high speed processing of large amounts of ordered parallel data, including spatial translation by shifting or sliding of bits vertically or horizontally to neighboring processing elements.

Fung, L. W. (inventor)

1983-01-01

202

Parallel hierarchical global illumination  

SciTech Connect

Solving the global illumination problem is equivalent to determining the intensity of every wavelength of light in all directions at every point in a given scene. The complexity of the problem has led researchers to use approximation methods for solving the problem on serial computers. Rather than using an approximation method, such as backward ray tracing or radiosity, the authors have chosen to solve the Rendering Equation by direct simulation of light transport from the light sources. This paper presents an algorithm that solves the Rendering Equation to any desired accuracy, and can be run in parallel on distributed memory or shared memory computer systems with excellent scaling properties. It appears superior in both speed and physical correctness to recent published methods involving bidirectional ray tracing or hybrid treatments of diffuse and specular surfaces. Like progressive radiosity methods, it dynamically refines the geometry decomposition where required, but does so without the excessive storage requirements for ray histories. The algorithm, called Photon, produces a scene which converges to the global illumination solution. This amounts to a huge task for a 1997-vintage serial computer, but using the power of a parallel supercomputer significantly reduces the time required to generate a solution. Currently, Photon can be run on most parallel environments from a shared memory multiprocessor to a parallel supercomputer, as well as on clusters of heterogeneous workstations.

Snell, Q.O.

1997-10-08

203

Parallel Traveling Salesman Problem  

NSDL National Science Digital Library

The traveling salesman problem is a classic optimization problem in which one seeks to minimize the path taken by a salesman in traveling between N cities, where the salesman stops at each city one and only one time, never retracing his/her route. This implementation is designed to run on UNIX systems with X-Windows, and includes parallelization using MPI.

Joiner, David; Hassinger, Jonathan

204

Parallelism and evolutionary algorithms  

Microsoft Academic Search

This paper contains a modern vision of the paral- lelization techniques used for evolutionary algorithms (EAs). The work is motivated by two fundamental facts: first, the different families of EAs have naturally converged in the last decade while parallel EAs (PEAs) seem still to lack unified studies, and second, there is a large number of improvements in these algorithms and

Enrique Alba; Marco Tomassini

2002-01-01

205

Massively Parallel Ionization of Extended Atomic Systems  

NASA Astrophysics Data System (ADS)

Massively parallel ionization of many atoms in a cluster or biomolecule is identified as a new phenomenon of light-matter interaction which becomes feasible through short and intense FEL pulses. Almost simultaneously emitted from the illuminated target the photo-electrons can have such a high density that they interact substantially even after photoionization. This interaction results in a characteristic electron spectrum which can be interpreted as a convolution of a mean-field electron dynamics and binary electron-electron collisions. We demonstrate that this universal spectrum can be obtained analytically by summing synthetic two-body Coulomb collision events. Moreover, we propose an experiment with hydrogen clusters to observe massively parallel ionization.

Gnodtke, Christian; Saalmann, Ulf; Rost, Jan-Michael

2012-04-01

206

Scalable Parallel Volume Raycasting for Nonrectilinear Computational Grids  

E-print Network

tools in the future, ultimately leading to the ability to interactively steer scientific computationsScalable Parallel Volume Raycasting for Nonrectilinear Computational Grids Judy Challinger Computer Engineering & Information Sciences University of California, Santa Cruz Santa Cruz, CA 95064 USA judy

Challinger, Judy

207

Parallel dichotomy algorithm for solving tridiagonal SLAEs  

E-print Network

A parallel algorithm for solving a series of matrix equations with a constant tridiagonal matrix and different right-hand sides is proposed and studied. The process of solving the problem is represented in two steps. The first preliminary step is fixing some rows of the inverse matrix of SLAEs. The second step consists in calculating solutions for all right-hand sides. For reducing the communication interactions, based on the formulated and proved main parallel sweep theorem, we propose an original algorithm for calculating share components of the solution vector. Theoretical estimates validating the efficiency of the approach for both the common- and distributed-memory supercomputers are obtained. Direct and iterative methods of solving a 2D Poisson equation, which include procedures of tridiagonal matrix inversion, are realized using the mpi technology. Results of computational experiments on a multicomputer demonstrate a high efficiency and scalability of the parallel sweep algorithm.

Terekhov, Andrew

2009-01-01

208

Parallel dichotomy algorithm for solving tridiagonal SLAEs  

E-print Network

A parallel algorithm for solving a series of matrix equations with a constant tridiagonal matrix and different right-hand sides is proposed and studied. The process of solving the problem is represented in two steps. The first preliminary step is fixing some rows of the inverse matrix of SLAEs. The second step consists in calculating solutions for all right-hand sides. For reducing the communication interactions, based on the formulated and proved main parallel sweep theorem, we propose an original algorithm for calculating share components of the solution vector. Theoretical estimates validating the efficiency of the approach for both the common- and distributed-memory supercomputers are obtained. Direct and iterative methods of solving a 2D Poisson equation, which include procedures of tridiagonal matrix inversion, are realized using the mpi technology. Results of computational experiments on a multicomputer demonstrate a high efficiency and scalability of the parallel sweep algorithm.

Andrew Terekhov

2009-01-19

209

Comprehensive Study on Tip Vortex with Lateral Jet Flow  

NASA Astrophysics Data System (ADS)

Comprehensive numerical and experimental investigations of tip vortical characteristics were conducted for lateral tip jet flow over a fixed wing as a step to reduce blade vortex interaction noise. The tip vortex of a NACA0012 blade was measured and visualized for the fundamental study of tip vortical flow, and the results were compared with numerical data as a validation of numerical solvers. Three-dimensional compressible Euler/Navier-Stokes codes were used to calculate the effect of jet flow from the tip of an OLS (modified BHT 540) fixed blade at various freestream velocities and jet conditions. The results show that the jet flowing from the wing tip can diffuse the tip vortex enlarging the core size of tip vortex and weakening its strength. When applied to the blade vortex interaction phenomena, this enlarged and weak vortex can produce a lower pressure gradient on the blade surface, which means that the jet flow can effectively reduce blade vortex interaction noise.

Yang, Choongmo; Baek, Jehyun; Saito, Shigeru; Aoyama, Takashi

210

Parallel Anisotropic Tetrahedral Adaptation  

NASA Technical Reports Server (NTRS)

An adaptive method that robustly produces high aspect ratio tetrahedra to a general 3D metric specification without introducing hybrid semi-structured regions is presented. The elemental operators and higher-level logic is described with their respective domain-decomposed parallelizations. An anisotropic tetrahedral grid adaptation scheme is demonstrated for 1000-1 stretching for a simple cube geometry. This form of adaptation is applicable to more complex domain boundaries via a cut-cell approach as demonstrated by a parallel 3D supersonic simulation of a complex fighter aircraft. To avoid the assumptions and approximations required to form a metric to specify adaptation, an approach is introduced that directly evaluates interpolation error. The grid is adapted to reduce and equidistribute this interpolation error calculation without the use of an intervening anisotropic metric. Direct interpolation error adaptation is illustrated for 1D and 3D domains.

Park, Michael A.; Darmofal, David L.

2008-01-01

211

Parallel Consensual Neural Networks  

NASA Technical Reports Server (NTRS)

A new neural network architecture is proposed and applied in classification of remote sensing/geographic data from multiple sources. The new architecture is called the parallel consensual neural network and its relation to hierarchical and ensemble neural networks is discussed. The parallel consensual neural network architecture is based on statistical consensus theory. The input data are transformed several times and the different transformed data are applied as if they were independent inputs and are classified using stage neural networks. Finally, the outputs from the stage networks are then weighted and combined to make a decision. Experimental results based on remote sensing data and geographic data are given. The performance of the consensual neural network architecture is compared to that of a two-layer (one hidden layer) conjugate-gradient backpropagation neural network. The results with the proposed neural network architecture compare favorably in terms of classification accuracy to the backpropagation method.

Benediktsson, J. A.; Sveinsson, J. R.; Ersoy, O. K.; Swain, P. H.

1993-01-01

212

Parallel Transports in Webs  

E-print Network

For connected reductive linear algebraic structure groups it is proven that every web is holonomically isolated. The possible tuples of parallel transports in a web form a Lie subgroup of the corresponding power of the structure group. This Lie subgroup is explicitly calculated and turns out to be independent of the chosen local trivializations. Moreover, explicit necessary and sufficient criteria for the holonomical independence of webs are derived. The results above can even be sharpened: Given an arbitrary neighbourhood of the base points of a web, then this neighbourhood contains some segments of the web whose parameter intervals coincide, but do not include 0 (that corresponds to the base points of the web), and whose parallel transports already form the same Lie subgroup as those of the full web do.

Christian Fleischhack

2003-03-31

213

Parallel multilevel preconditioners  

SciTech Connect

In this paper, we shall report on some techniques for the development of preconditioners for the discrete systems which arise in the approximation of solutions to elliptic boundary value problems. Here we shall only state the resulting theorems. It has been demonstrated that preconditioned iteration techniques often lead to the most computationally effective algorithms for the solution of the large algebraic systems corresponding to boundary value problems in two and three dimensional Euclidean space. The use of preconditioned iteration will become even more important on computers with parallel architecture. This paper discusses an approach for developing completely parallel multilevel preconditioners. In order to illustrate the resulting algorithms, we shall describe the simplest application of the technique to a model elliptic problem.

Bramble, J.H.; Pasciak, J.E.; Xu, Jinchao.

1989-01-01

214

Parallelization: Infectious Disease  

NSDL National Science Digital Library

Epidemiology is the study of infectious disease. Infectious diseases are said to be "contagious" among people if they are transmittable from one person to another. Epidemiologists can use models to assist them in predicting the behavior of infectious diseases. This module will develop a simple agent-based infectious disease model, develop a parallel algorithm based on the model, provide a coded implementation for the algorithm, and explore the scaling of the coded implementation on high performance cluster resources.

Weeden, Aaron

215

Visual rays are parallel.  

PubMed

We show that human observers using monocular viewing treat the pencil of 'visual rays' that diverges from the vantage point as experientally parallel. This oddity becomes very noticeable in the case of wide-angle presentations, where the angle subtended by a pair of visual rays may be as large as the angular size of the display. In our presentations such angles subtended over 100 deg. There are various ways to demonstrate the effect; in this study we measure the attitudes of pictorial objects that appear to be situated in mutually parallel attitudes in pictorial space. Our finding is that such objects appear parallel if they are similarly oriented with respect to the local visual rays. This leads to 'errors' in the judgment of mutual orientations of up to 100 deg. Although this appears to be the first quantitative study of the effect, we trace it to qualitative reports by Helmholtz (late 19th century) and Kepler (early 17th century) as well as speculation by early authors (AD 500). The effect has apparently been noticed by visual artists from the late middle ages to the present day. PMID:21125944

Koenderink, Jan; van Doorn, Andrea; de Ridder, Huib; Oomes, Stijn

2010-01-01

216

Darwinian Evolution in Parallel Universes: A Parallel Genetic Algorithm for  

E-print Network

Darwinian Evolution in Parallel Universes: A Parallel Genetic Algorithm for Variable Selection Mu outcome of interest commonly arises in various industrial engineering applications. The genetic algorithm modification. Our idea is to run a number of GAs in parallel without allowing each GA to fully converge

Zhu, Mu

217

The STAPL Parallel Container Framework  

E-print Network

, and thread safety. This dissertation presents the STAPL Parallel Container Framework (PCF), which is designed to facilitate the development of generic parallel containers. We introduce a set of concepts and a methodology for assembling a pContainer from...

Tanase, Ilie Gabriel

2012-02-14

218

The Galley Parallel File System  

NASA Technical Reports Server (NTRS)

As the I/O needs of parallel scientific applications increase, file systems for multiprocessors are being designed to provide applications with parallel access to multiple disks. Many parallel file systems present applications with a conventional Unix-like interface that allows the application to access multiple disks transparently. The interface conceals the parallelism within the file system, which increases the ease of programmability, but makes it difficult or impossible for sophisticated programmers and libraries to use knowledge about their I/O needs to exploit that parallelism. Furthermore, most current parallel file systems are optimized for a different workload than they are being asked to support. We introduce Galley, a new parallel file system that is intended to efficiently support realistic parallel workloads. We discuss Galley's file structure and application interface, as well as an application that has been implemented using that interface.

Nieuwejaar, Nils; Kotz, David

1996-01-01

219

On parallel machine scheduling 1  

E-print Network

On parallel machine scheduling 1 machines with setup times. The setup has to be performed by a single server. The objective is to minimize even for the case of two identical parallel machines. This paper presents a pseudopolynomial

Magdeburg, Universität

220

Time sharing massively parallel machines. Draft  

SciTech Connect

As part of the Massively Parallel Computing Initiative (MPCI) at the Lawrence Livermore National Laboratory, the authors have developed a simple, effective and portable time sharing mechanism by scheduling gangs of processes on tightly coupled parallel machines. By time-sharing the resources, the system interleaves production and interactive jobs. Immediate priority is given to interactive use, maintaining good response time. Production jobs are scheduled during idle periods, making use of the otherwise unused resources. In this paper the authors discuss their experience with gang scheduling over the 3 year life-time of the project. In section 2, they motivate the project and discuss some of its details. Section 3.0 describes the general scheduling problem and how gang scheduling addresses it. In section 4.0, they describe the implementation. Section 8.0 presents results culled over the lifetime of the project. They conclude this paper with some observations and possible future directions.

Gorda, B.; Wolski, R.

1995-03-01

221

Parallel Pascal - An extended Pascal for parallel computers  

NASA Technical Reports Server (NTRS)

Parallel Pascal is an extended version of the conventional serial Pascal programming language which includes a convenient syntax for specifying array operations. It is upward compatible with standard Pascal and involves only a small number of carefully chosen new features. Parallel Pascal was developed to reduce the semantic gap between standard Pascal and a large range of highly parallel computers. Two important design goals of Parallel Pascal were efficiency and portability. Portability is particularly difficult to achieve since different parallel computers frequently have very different capabilities.

Reeves, A. P.

1984-01-01

222

CSM parallel structural methods research  

NASA Technical Reports Server (NTRS)

Parallel structural methods, research team activities, advanced architecture computers for parallel computational structural mechanics (CSM) research, the FLEX/32 multicomputer, a parallel structural analyses testbed, blade-stiffened aluminum panel with a circular cutout and the dynamic characteristics of a 60 meter, 54-bay, 3-longeron deployable truss beam are among the topics discussed.

Storaasli, Olaf O.

1989-01-01

223

Roo: A parallel theorem prover  

SciTech Connect

We describe a parallel theorem prover based on the Argonne theorem-proving system OTTER. The parallel system, called Roo, runs on shared-memory multiprocessors such as the Sequent Symmetry. We explain the parallel algorithm used and give performance results that demonstrate near-linear speedups on large problems.

Lusk, E.L.; McCune, W.W.; Slaney, J.K.

1991-11-01

224

Parallel Kinematic Machines (PKM)  

SciTech Connect

The purpose of this 3-year cooperative research project was to develop a parallel kinematic machining (PKM) capability for complex parts that normally require expensive multiple setups on conventional orthogonal machine tools. This non-conventional, non-orthogonal machining approach is based on a 6-axis positioning system commonly referred to as a hexapod. Sandia National Laboratories/New Mexico (SNL/NM) was the lead site responsible for a multitude of projects that defined the machining parameters and detailed the metrology of the hexapod. The role of the Kansas City Plant (KCP) in this project was limited to evaluating the application of this unique technology to production applications.

Henry, R.S.

2000-03-17

225

Parallel Processing System  

NASA Technical Reports Server (NTRS)

In order to process very high resolution image data from spacecraft sensors, Goddard Space Flight Center commissioned the development of a Massively Parallel Processor (MPP) based upon simultaneous processing of image picture elements (pixels) rather than serial processing. It resulted in a considerable increase in computational speed. MasPar Computer Corporation's MasPar MP-1 incorporates this technology, allowing users to attack a variety of computationally-intensive problems. The MP-1 is no longer manufactured but has been replaced by the MP-2, a more advanced model.

1991-01-01

226

Parallel Eclipse Project Checkout  

NASA Technical Reports Server (NTRS)

Parallel Eclipse Project Checkout (PEPC) is a program written to leverage parallelism and to automate the checkout process of plug-ins created in Eclipse RCP (Rich Client Platform). Eclipse plug-ins can be aggregated in a feature project. This innovation digests a feature description (xml file) and automatically checks out all of the plug-ins listed in the feature. This resolves the issue of manually checking out each plug-in required to work on the project. To minimize the amount of time necessary to checkout the plug-ins, this program makes the plug-in checkouts parallel. After parsing the feature, a request to checkout for each plug-in in the feature has been inserted. These requests are handled by a thread pool with a configurable number of threads. By checking out the plug-ins in parallel, the checkout process is streamlined before getting started on the project. For instance, projects that took 30 minutes to checkout now take less than 5 minutes. The effect is especially clear on a Mac, which has a network monitor displaying the bandwidth use. When running the client from a developer s home, the checkout process now saturates the bandwidth in order to get all the plug-ins checked out as fast as possible. For comparison, a checkout process that ranged from 8-200 Kbps from a developer s home is now able to saturate a pipe of 1.3 Mbps, resulting in significantly faster checkouts. Eclipse IDE (integrated development environment) tries to build a project as soon as it is downloaded. As part of another optimization, this innovation programmatically tells Eclipse to stop building while checkouts are happening, which dramatically reduces lock contention and enables plug-ins to continue downloading until all of them finish. Furthermore, the software re-enables automatic building, and forces Eclipse to do a clean build once it finishes checking out all of the plug-ins. This software is fully generic and does not contain any NASA-specific code. It can be applied to any Eclipse-based repository with a similar structure. It also can apply build parameters and preferences automatically at the end of the checkout.

Crockett, Thomas M.; Joswig, Joseph C.; Shams, Khawaja S.; Powell, Mark W.; Bachmann, Andrew G.

2011-01-01

227

Tolerant (parallel) Programming  

NASA Technical Reports Server (NTRS)

In order to be truly portable, a program must be tolerant of a wide range of development and execution environments, and a parallel program is just one which must be tolerant of a very wide range. This paper first defines the term "tolerant programming", then describes many layers of tools to accomplish it. The primary focus is on F-Nets, a formal model for expressing computation as a folded partial-ordering of operations, thereby providing an architecture-independent expression of tolerant parallel algorithms. For implementing F-Nets, Cooperative Data Sharing (CDS) is a subroutine package for implementing communication efficiently in a large number of environments (e.g. shared memory and message passing). Software Cabling (SC), a very-high-level graphical programming language for building large F-Nets, possesses many of the features normally expected from today's computer languages (e.g. data abstraction, array operations). Finally, L2(sup 3) is a CASE tool which facilitates the construction, compilation, execution, and debugging of SC programs.

DiNucci, David C.; Bailey, David H. (Technical Monitor)

1997-01-01

228

Parallel Computing in SCALE  

SciTech Connect

The SCALE computational architecture has remained basically the same since its inception 30 years ago, although constituent modules and capabilities have changed significantly. This SCALE concept was intended to provide a framework whereby independent codes can be linked to provide a more comprehensive capability than possible with the individual programs - allowing flexibility to address a wide variety of applications. However, the current system was designed originally for mainframe computers with a single CPU and with significantly less memory than today's personal computers. It has been recognized that the present SCALE computation system could be restructured to take advantage of modern hardware and software capabilities, while retaining many of the modular features of the present system. Preliminary work is being done to define specifications and capabilities for a more advanced computational architecture. This paper describes the state of current SCALE development activities and plans for future development. With the release of SCALE 6.1 in 2010, a new phase of evolutionary development will be available to SCALE users within the TRITON and NEWT modules. The SCALE (Standardized Computer Analyses for Licensing Evaluation) code system developed by Oak Ridge National Laboratory (ORNL) provides a comprehensive and integrated package of codes and nuclear data for a wide range of applications in criticality safety, reactor physics, shielding, isotopic depletion and decay, and sensitivity/uncertainty (S/U) analysis. Over the last three years, since the release of version 5.1 in 2006, several important new codes have been introduced within SCALE, and significant advances applied to existing codes. Many of these new features became available with the release of SCALE 6.0 in early 2009. However, beginning with SCALE 6.1, a first generation of parallel computing is being introduced. In addition to near-term improvements, a plan for longer term SCALE enhancement activities has been developed to provide an integrated framework for future methods development. Some of the major components of the SCALE parallel computing development plan are parallelization and multithreading of computationally intensive modules and redesign of the fundamental SCALE computational architecture.

DeHart, Mark D [ORNL] [ORNL; Williams, Mark L [ORNL] [ORNL; Bowman, Stephen M [ORNL] [ORNL

2010-01-01

229

Toward Parallel Document Clustering  

SciTech Connect

A key challenge to automated clustering of documents in large text corpora is the high cost of comparing documents in a multimillion dimensional document space. The Anchors Hierarchy is a fast data structure and algorithm for localizing data based on a triangle inequality obeying distance metric, the algorithm strives to minimize the number of distance calculations needed to cluster the documents into “anchors” around reference documents called “pivots”. We extend the original algorithm to increase the amount of available parallelism and consider two implementations: a complex data structure which affords efficient searching, and a simple data structure which requires repeated sorting. The sorting implementation is integrated with a text corpora “Bag of Words” program and initial performance results of end-to-end a document processing workflow are reported.

Mogill, Jace A.; Haglin, David J.

2011-09-01

230

Run-time methods for parallelizing partially parallel loops  

Microsoft Academic Search

In this paper we give a new run-time technique for finding an optimal parallel execution schedule for a partially parallel loop, i.e., a loop whose parallelization requires synchronization to ensure that the iterations are executed in the correct order. Given the original loop, the compiler generates inspector code that performs run-time preprocessing of the loop's access pattern, and scheduler code

Lawrence Rauchwergert; Nancy M. Amato; David A. Paduat

1995-01-01

231

Parallel TreeSPH  

NASA Astrophysics Data System (ADS)

We describe PTreeSPH, a gravity treecode combined with an SPH hydrodynamics code designed for parallel supercomputers having distributed memory. Our computational algorithm is based on the popular TreeSPH code of Hernquist & Katz (1989)[ApJS, 70, 419]. PTreeSPH utilizes a domain decomposition procedure and a synchronous hypercube communication paradigm to build self-contained subvolumes of the simulation on each processor at every timestep. Computations then proceed in a manner analogous to a serial code. We use the Message Passing Interface (MPI) communications package, making our code easily portable to a variety of parallel systems. PTreeSPH uses individual smoothing lengths and timesteps, with a communication algorithm designed to minimize exchange of information while still providing all information required to accurately perform SPH computations. We have incorporated periodic boundary conditions with forces calculated using a quadrupole Ewald summation method, and comoving integration under a variety of cosmologies. Following algorithms presented in Katz et al. (1996)[ApJS, 105, 19], we have also included radiative cooling, heating from a parameterized ionizing background, and star formation. A cosmological simulation from z = 49 to z = 2 with 64 3 gas particles and 64 3 dark matter particles requires ˜ 1800 node-hours on a Cray T3D, with a communications overhead of ˜ 8%, load balanced to ? 95% level. When used on the new Cray T3E, this code will be capable of performing cosmological hydrodynamical simulations down to z = 0 with ˜ 2 × 10 6 particles, or to z = 2 with ˜ 10 7 particles, in a reasonable amount of time. Even larger simulations will be practical in situations where the matter is not highly clustered or when periodic boundaries are not required.

Davé, Romeel; Dubinski, John; Hernquist, Lars

1997-08-01

232

Falcon: On-line Monitoring and Steering of Parallel Programs  

Microsoft Academic Search

Advances in high performance computing, communications, and user interfaces are enabling developers to construct increasingly interactive high performance applications. The Falcon system presented in this paper supports such interactivity by providing runtime libraries, tools, and user interfaces that jointly permit the on-line monitoring and steering of large-scale parallel codes. The principal aspects of Falcon described in this paper are its

Weiming Gu; Greg Eisenhauer; Karsten Schwan; Jeffrey Vetter

1995-01-01

233

Using Motivational Interviewing Techniques to Address Parallel Process in Supervision  

ERIC Educational Resources Information Center

Supervision offers a distinct opportunity to experience the interconnection of counselor-client and counselor-supervisor interactions. One product of this network of interactions is parallel process, a phenomenon by which counselors unconsciously identify with their clients and subsequently present to their supervisors in a similar fashion…

Giordano, Amanda; Clarke, Philip; Borders, L. DiAnne

2013-01-01

234

"Serial" effects in parallel models of reading  

PubMed Central

There is now considerable evidence showing that the time to read a word out loud is influenced by an interaction between orthographic length and lexicality. Given that length effects are interpreted by advocates of dual-route models as evidence of serial processing this would seem to pose a serious challenge to models of single word reading which postulate a common parallel processing mechanism for reading both words and nonwords (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001; Rastle, Havelka, Wydell, Coltheart, & Besner, 2009). However, an alternative explanation of these data is that visual processes outside the scope of existing parallel models are responsible for generating the word-length related phenomena (Seidenberg & Plaut, 1998). Here we demonstrate that a parallel model of single word reading can account for the differential word-length effects found in the naming latencies of words and nonwords, provided that it includes a mapping from visual to orthographic representations, and that the nature of those orthographic representations are not preconstrained. The model can also simulate other supposedly “serial” effects. The overall findings were consistent with the view that visual processing contributes substantially to the word-length effects in normal reading and provided evidence to support the single-route theory which assumes words and nonwords are processed in parallel by a common mechanism. PMID:22343366

Chang, Ya-Ning; Furber, Steve; Welbourne, Stephen

2012-01-01

235

Parallel structural optimization with different parallel analysis interfaces  

NASA Technical Reports Server (NTRS)

The real benefit of structural optimization techniques is in the application of these techniques to large structures such as full vehicles or full aircraft. For these structures, however, the sequential computer's time and memory requirements prohibit the solutions. With the rapid development of parallel computers, parallel processing of large scale structural optimization problems is achievable. In this paper we discuss the parallel processing of structural optimization problems with parallel structural analysis. Two different types of interface between the optimization and analysis routines are developed and tested.

El-Sayed, Mohamed E. M.; Hsiung, Ching-Kuo

1990-01-01

236

Exploiting Parallelism to Accelerate Keyword Search on Deep-Web Sources  

Microsoft Academic Search

Increasingly, biological data is being shared over the deep web. Many biological queries can only be answered by successively search- ing a number of distinct web-sites. This paper introduces a system that exploits parallelization for accelerating search over multiple deep web data sources. An interactive, two-stage multi-threading system is devel- oped to achieve task parallelization, thread parallelization, and pipelined parallelization.

Tantan Liu; Fan Wang; Gagan Agrawal

2009-01-01

237

PARALLEL DATABASE MACHINES Kjell Bratbergsengen  

E-print Network

PARALLEL DATABASE MACHINES Kjell Bratbergsengen Department of Computer Systems and Telematics in the Database Technology Group at The Department of Computer Systems and Telematics, NTH has been supported

238

Parallel processing and expert systems  

NASA Technical Reports Server (NTRS)

Whether it be monitoring the thermal subsystem of Space Station Freedom, or controlling the navigation of the autonomous rover on Mars, NASA missions in the 90's cannot enjoy an increased level of autonomy without the efficient use of expert systems. Merely increasing the computational speed of uniprocessors may not be able to guarantee that real time demands are met for large expert systems. Speed-up via parallel processing must be pursued alongside the optimization of sequential implementations. Prototypes of parallel expert systems have been built at universities and industrial labs in the U.S. and Japan. The state-of-the-art research in progress related to parallel execution of expert systems was surveyed. The survey is divided into three major sections: (1) multiprocessors for parallel expert systems; (2) parallel languages for symbolic computations; and (3) measurements of parallelism of expert system. Results to date indicate that the parallelism achieved for these systems is small. In order to obtain greater speed-ups, data parallelism and application parallelism must be exploited.

Yan, Jerry C.; Lau, Sonie

1991-01-01

239

Parallel computation with the force  

NASA Technical Reports Server (NTRS)

A methodology, called the force, supports the construction of programs to be executed in parallel by a force of processes. The number of processes in the force is unspecified, but potentially very large. The force idea is embodied in a set of macros which produce multiproceossor FORTRAN code and has been studied on two shared memory multiprocessors of fairly different character. The method has simplified the writing of highly parallel programs within a limited class of parallel algorithms and is being extended to cover a broader class. The individual parallel constructs which comprise the force methodology are discussed. Of central concern are their semantics, implementation on different architectures and performance implications.

Jordan, H. F.

1985-01-01

240

Parallel Bifold: Large-Scale Parallel Pattern Mining with Constraints  

E-print Network

Parallel Bifold: Large-Scale Parallel Pattern Mining with Constraints Mohammad El-Hajj, Osmar R. Za¨iane Department of Computing Science, UofA, Edmonton, AB, Canada {mohammad, zaiane}@cs.ualberta.ca University Of Alberta Abstract. When computationally feasible, mining huge databases pro- duces tremendously large

Zaiane, Osmar R.

241

Parallel Programming in the Age of Ubiquitous Parallelism  

NASA Astrophysics Data System (ADS)

Multicore and manycore processors are now ubiquitous, but parallel programming remains as difficult as it was 30-40 years ago. During this time, our community has explored many promising approaches including functional and dataflow languages, logic programming, and automatic parallelization using program analysis and restructuring, but none of these approaches has succeeded except in a few niche application areas. In this talk, I will argue that these problems arise largely from the computation-centric foundations and abstractions that we currently use to think about parallelism. In their place, I will propose a novel data-centric foundation for parallel programming called the operator formulation in which algorithms are described in terms of actions on data. The operator formulation shows that a generalized form of data-parallelism called amorphous data-parallelism is ubiquitous even in complex, irregular graph applications such as mesh generation/refinement/partitioning and SAT solvers. Regular algorithms emerge as a special case of irregular ones, and many application-specific optimization techniques can be generalized to a broader context. The operator formulation also leads to a structural analysis of algorithms called TAO-analysis that provides implementation guidelines for exploiting parallelism efficiently. Finally, I will describe a system called Galois based on these ideas for exploiting amorphous data-parallelism on multicores and GPUs

Pingali, Keshav

2014-04-01

242

Parallelization of irregularly coupled regular meshes  

NASA Technical Reports Server (NTRS)

Regular meshes are frequently used for modeling physical phenomena on both serial and parallel computers. One advantage of regular meshes is that efficient discretization schemes can be implemented in a straight forward manner. However, geometrically-complex objects, such as aircraft, cannot be easily described using a single regular mesh. Multiple interacting regular meshes are frequently used to describe complex geometries. Each mesh models a subregion of the physical domain. The meshes, or subdomains, can be processed in parallel, with periodic updates carried out to move information between the coupled meshes. In many cases, there are a relatively small number (one to a few dozen) subdomains, so that each subdomain may also be partitioned among several processors. We outline a composite run-time/compile-time approach for supporting these problems efficiently on distributed-memory machines. These methods are described in the context of a multiblock fluid dynamics problem developed at LaRC.

Chase, Craig; Crowley, Kay; Saltz, Joel; Reeves, Anthony

1992-01-01

243

Tile-based Level of Detail for the Parallel Age  

SciTech Connect

Today's PCs incorporate multiple CPUs and GPUs and are easily arranged in clusters for high-performance, interactive graphics. We present an approach based on hierarchical, screen-space tiles to parallelizing rendering with level of detail. Adapt tiles, render tiles, and machine tiles are associated with CPUs, GPUs, and PCs, respectively, to efficiently parallelize the workload with good resource utilization. Adaptive tile sizes provide load balancing while our level of detail system allows total and independent management of the load on CPUs and GPUs. We demonstrate our approach on parallel configurations consisting of both single PCs and a cluster of PCs.

Niski, K; Cohen, J D

2007-08-15

244

A Parallel Program Analysis Framework for the ACTS Toolkit  

SciTech Connect

OAK 270 - The final report summarizes the technical progress achieved during the project. A Parallel Program Analysis Framework for the acts toolkit, referred to as the TAU project. Described are the results in four work areas: (1) creation of a performance system for integrated instrumentation, measurement, analysis and visualization. (2) development of a performance measurement system for parallel profiling and tracing (3) development of an advanced program analysis system to enable creation of source-based performance and programing tools (4) development of parallel program interaction technology for accessing, performance information and application data during execution.

Allen D. Malony

2002-06-21

245

High Performance Parallel Architectures  

NASA Technical Reports Server (NTRS)

Traditional remote sensing instruments are multispectral, where observations are collected at a few different spectral bands. Recently, many hyperspectral instruments, that can collect observations at hundreds of bands, have been operational. Furthermore, there have been ongoing research efforts on ultraspectral instruments that can produce observations at thousands of spectral bands. While these remote sensing technology developments hold great promise for new findings in the area of Earth and space science, they present many challenges. These include the need for faster processing of such increased data volumes, and methods for data reduction. Dimension Reduction is a spectral transformation, aimed at concentrating the vital information and discarding redundant data. One such transformation, which is widely used in remote sensing, is the Principal Components Analysis (PCA). This report summarizes our progress on the development of a parallel PCA and its implementation on two Beowulf cluster configuration; one with fast Ethernet switch and the other with a Myrinet interconnection. Details of the implementation and performance results, for typical sets of multispectral and hyperspectral NASA remote sensing data, are presented and analyzed based on the algorithm requirements and the underlying machine configuration. It will be shown that the PCA application is quite challenging and hard to scale on Ethernet-based clusters. However, the measurements also show that a high- performance interconnection network, such as Myrinet, better matches the high communication demand of PCA and can lead to a more efficient PCA execution.

El-Ghazawi, Tarek; Kaewpijit, Sinthop

1998-01-01

246

Study Of Helicopter-Tail-Rotor Noise  

NASA Technical Reports Server (NTRS)

Report describes findings of experiment in generation of impulsive noise and fluctuating blade loads by helicopter tail rotor interacting with vortexes from main rotor. Experiment used model rotor and isolated vortex and designed to isolate blade/vortex interaction noise from other types of rotor noise.

Ahmadi, Ali R.; Beranek, Bolt

1988-01-01

247

Symbolic analysis for parallelizing compilers  

Microsoft Academic Search

The notion of dependence captures that most important properties of a program for efficient execution on parallel computers. The dependence structure of a program defines that necessary constraints of the order of execution of the program components and provides sufficient information for the exploitation of the available parallelism. Static discovery and management of the dependence structure of programs save a

Mohammad R. Haghighat; Constantine D. Polychronopoulos

1996-01-01

248

Parallelism in random access machines  

Microsoft Academic Search

A model of computation based on random access machines operating in parallel and sharing a common memory is presented. The computational power of this model is related to that of traditional models. In particular, deterministic parallel RAM's can accept in polynomial time exactly the sets accepted by polynomial tape bounded Turing machines; nondeterministic RAM's can accept in polynomial time exactly

Steven Fortune; James Wyllie

1978-01-01

249

Fast data parallel polygon rendering  

Microsoft Academic Search

This paper describes a data parallel method for polygon rendering on a massively parallel machine. This method, based on a simple shading model, is targeted for applications which require very fast rendering for extremely large sets of polygons. Such sets are found in many scientific visualization applications. The renderer can handle arbitrarily complex polygons which need not be meshed. Issues

Frank A. Ortega; Charles D. Hansen; James P. Ahrens

1993-01-01

250

Parallelizing Monte Carlo with PMC  

SciTech Connect

PMC (Parallel Monte Carlo) is a system of generic interface routines that allows easy porting of Monte Carlo packages of large-scale physics simulation codes to Massively Parallel Processor (MPP) computers. By loading various versions of PMC, simulation code developers can configure their codes to run in several modes: serial, Monte Carlo runs on the same processor as the rest of the code; parallel, Monte Carlo runs in parallel across many processors of the MPP with the rest of the code running on other MPP processor(s); distributed, Monte Carlo runs in parallel across many processors of the MPP with the rest of the code running on a different machine. This multi-mode approach allows maintenance of a single simulation code source regardless of the target machine. PMC handles passing of messages between nodes on the MPP, passing of messages between a different machine and the MPP, distributing work between nodes, and providing independent, reproducible sequences of random numbers. Several production codes have been parallelized under the PMC system. Excellent parallel efficiency in both the distributed and parallel modes results if sufficient workload is available per processor. Experiences with a Monte Carlo photonics demonstration code and a Monte Carlo neutronics package are described.

Rathkopf, J.A.; Jones, T.R.; Nessett, D.M.; Stanberry, L.C.

1994-11-01

251

Loading databases using dataflow parallelism  

Microsoft Academic Search

This paper describes a parallel database load prototype for Digital's Rdb database product. The prototype takes a dataflow approach to database parallelism. It includes an explorer that discovers and records the cluster configuration in a database, a client CUI interface that gathers the load job description from the user and from the Rdb catalogs, and an optimizer that picks the

Tom Barclay; Robert Barnes; Jim Gray; Prakash Sundaresan

1994-01-01

252

The Galley Parallel File System  

NASA Technical Reports Server (NTRS)

Most current multiprocessor file systems are designed to use multiple disks in parallel, using the high aggregate bandwidth to meet the growing I/0 requirements of parallel scientific applications. Many multiprocessor file systems provide applications with a conventional Unix-like interface, allowing the application to access multiple disks transparently. This interface conceals the parallelism within the file system, increasing the ease of programmability, but making it difficult or impossible for sophisticated programmers and libraries to use knowledge about their I/O needs to exploit that parallelism. In addition to providing an insufficient interface, most current multiprocessor file systems are optimized for a different workload than they are being asked to support. We introduce Galley, a new parallel file system that is intended to efficiently support realistic scientific multiprocessor workloads. We discuss Galley's file structure and application interface, as well as the performance advantages offered by that interface.

Nieuwejaar, Nils; Kotz, David

1996-01-01

253

Parallel contingency statistics with Titan.  

SciTech Connect

This report summarizes existing statistical engines in VTK/Titan and presents the recently parallelized contingency statistics engine. It is a sequel to [PT08] and [BPRT09] which studied the parallel descriptive, correlative, multi-correlative, and principal component analysis engines. The ease of use of this new parallel engines is illustrated by the means of C++ code snippets. Furthermore, this report justifies the design of these engines with parallel scalability in mind; however, the very nature of contingency tables prevent this new engine from exhibiting optimal parallel speed-up as the aforementioned engines do. This report therefore discusses the design trade-offs we made and study performance with up to 200 processors.

Thompson, David C.; Pebay, Philippe Pierre

2009-09-01

254

Parallel processing for control applications  

SciTech Connect

Parallel processing has been a topic of discussion in computer science circles for decades. Using more than one single computer to control a process has many advantages that compensate for the additional cost. Initially multiple computers were used to attain higher speeds. A single cpu could not perform all of the operations necessary for real time operation. As technology progressed and cpu's became faster, the speed issue became less significant. The additional processing capabilities however continue to make high speeds an attractive element of parallel processing. Another reason for multiple processors is reliability. For the purpose of this discussion, reliability and robustness will be the focal paint. Most contemporary conceptions of parallel processing include visions of hundreds of single computers networked to provide 'computing power'. Indeed our own teraflop machines are built from large numbers of computers configured in a network (and thus limited by the network). There are many approaches to parallel configfirations and this presentation offers something slightly different from the contemporary networked model. In the world of embedded computers, which is a pervasive force in contemporary computer controls, there are many single chip computers available. If one backs away from the PC based parallel computing model and considers the possibilities of a parallel control device based on multiple single chip computers, a new area of possibilities becomes apparent. This study will look at the use of multiple single chip computers in a parallel configuration with emphasis placed on maximum reliability.

Telford, J. W. (John W.)

2001-01-01

255

Is Monte Carlo embarrassingly parallel?  

SciTech Connect

Monte Carlo is often stated as being embarrassingly parallel. However, running a Monte Carlo calculation, especially a reactor criticality calculation, in parallel using tens of processors shows a serious limitation in speedup and the execution time may even increase beyond a certain number of processors. In this paper the main causes of the loss of efficiency when using many processors are analyzed using a simple Monte Carlo program for criticality. The basic mechanism for parallel execution is MPI. One of the bottlenecks turn out to be the rendez-vous points in the parallel calculation used for synchronization and exchange of data between processors. This happens at least at the end of each cycle for fission source generation in order to collect the full fission source distribution for the next cycle and to estimate the effective multiplication factor, which is not only part of the requested results, but also input to the next cycle for population control. Basic improvements to overcome this limitation are suggested and tested. Also other time losses in the parallel calculation are identified. Moreover, the threading mechanism, which allows the parallel execution of tasks based on shared memory using OpenMP, is analyzed in detail. Recommendations are given to get the maximum efficiency out of a parallel Monte Carlo calculation. (authors)

Hoogenboom, J. E. [Delft Univ. of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Delft Nuclear Consultancy, IJsselzoom 2, 2902 LB Capelle aan den IJssel (Netherlands)

2012-07-01

256

THE PARALLEL JAVA 2 LIBRARY Parallel Programming in 100% Java  

E-print Network

, and reducers Parallel Java 2 cluster middleware Future work: · GPU support--GPU kernels written in C/CUDA, CPU Set main program. public void main (String[] args) throws Exception { // Validate command line

Kaminsky, Alan

257

EFFICIENT SCHEDULING OF PARALLEL JOBS ON MASSIVELY PARALLEL SYSTEMS  

SciTech Connect

We present buffered coscheduling, a new methodology to multitask parallel jobs in a message-passing environment and to develop parallel programs that can pave the way to the efficient implementation of a distributed operating system. Buffered coscheduling is based on three innovative techniques: communication buffering, strobing, and non-blocking communication. By leveraging these techniques, we can perform effective optimizations based on the global status of the parallel machine rather than on the limited knowledge available locally to each processor. The advantages of buffered coscheduling include higher resource utilization, reduced communication overhead, efficient implementation of low-control strategies and fault-tolerant protocols, accurate performance modeling, and a simplified yet still expressive parallel programming model. Preliminary experimental results show that buffered coscheduling is very effective in increasing the overall performance in the presence of load imbalance and communication-intensive workloads.

F. PETRINI; W. FENG

1999-09-01

258

Template based parallel checkpointing in a massively parallel computer system  

SciTech Connect

A method and apparatus for a template based parallel checkpoint save for a massively parallel super computer system using a parallel variation of the rsync protocol, and network broadcast. In preferred embodiments, the checkpoint data for each node is compared to a template checkpoint file that resides in the storage and that was previously produced. Embodiments herein greatly decrease the amount of data that must be transmitted and stored for faster checkpointing and increased efficiency of the computer system. Embodiments are directed to a parallel computer system with nodes arranged in a cluster with a high speed interconnect that can perform broadcast communication. The checkpoint contains a set of actual small data blocks with their corresponding checksums from all nodes in the system. The data blocks may be compressed using conventional non-lossy data compression algorithms to further reduce the overall checkpoint size.

Archer, Charles Jens (Rochester, MN); Inglett, Todd Alan (Rochester, MN)

2009-01-13

259

Parallel node placement method by bubble simulation  

NASA Astrophysics Data System (ADS)

An efficient Parallel Node Placement method by Bubble Simulation (PNPBS), employing METIS-based domain decomposition (DD) for an arbitrary number of processors is introduced. In accordance with the desired nodal density and Newton’s Second Law of Motion, automatic generation of node sets by bubble simulation has been demonstrated in previous work. Since the interaction force between nodes is short-range, for two distant nodes, their positions and velocities can be updated simultaneously and independently during dynamic simulation, which indicates the inherent property of parallelism, it is quite suitable for parallel computing. In this PNPBS method, the METIS-based DD scheme has been investigated for uniform and non-uniform node sets, and dynamic load balancing is obtained by evenly distributing work among the processors. For the nodes near the common interface of two neighboring subdomains, there is no need for special treatment after dynamic simulation. These nodes have good geometrical properties and a smooth density distribution which is desirable in the numerical solution of partial differential equations (PDEs). The results of numerical examples show that quasi linear speedup in the number of processors and high efficiency are achieved.

Nie, Yufeng; Zhang, Weiwei; Qi, Nan; Li, Yiqiang

2014-03-01

260

Parallel Strategies for Crash and Impact Simulations  

SciTech Connect

We describe a general strategy we have found effective for parallelizing solid mechanics simula- tions. Such simulations often have several computationally intensive parts, including finite element integration, detection of material contacts, and particle interaction if smoothed particle hydrody- namics is used to model highly deforming materials. The need to balance all of these computations simultaneously is a difficult challenge that has kept many commercial and government codes from being used effectively on parallel supercomputers with hundreds or thousands of processors. Our strategy is to load-balance each of the significant computations independently with whatever bal- ancing technique is most appropriate. The chief benefit is that each computation can be scalably paraIlelized. The drawback is the data exchange between processors and extra coding that must be written to maintain multiple decompositions in a single code. We discuss these trade-offs and give performance results showing this strategy has led to a parallel implementation of a widely-used solid mechanics code that can now be run efficiently on thousands of processors of the Pentium-based Sandia/Intel TFLOPS machine. We illustrate with several examples the kinds of high-resolution, million-element models that can now be simulated routinely. We also look to the future and dis- cuss what possibilities this new capabUity promises, as well as the new set of challenges it poses in material models, computational techniques, and computing infrastructure.

Attaway, S.; Brown, K.; Hendrickson, B.; Plimpton, S.

1998-12-07

261

Parallel inverse iteration with reorthogonalization  

SciTech Connect

A parallel method for finding orthogonal eigenvectors of real symmetric tridiagonal is described. The method uses inverse iteration with repeated Modified Gram-Schmidt (MGS) reorthogonalization of the unconverged iterates for clustered eigenvalues. This approach is more parallelizable than reorthogonalizing against fully converged eigenvectors, as is done by LAPACK`s current DSTEIN routine. The new method is found to provide accuracy and speed comparable to DSTEIN`s and to have good parallel scalability even for matrices with large clusters of eigenvalues. We present al results for residual and orthogonality tests, plus timings on IBM RS/6000 (sequential) and Intel Touchstone DELTA (parallel) computers.

Fann, G.I.; Littlefield, R.J.

1993-03-01

262

Parallel inverse iteration with reorthogonalization  

SciTech Connect

A parallel method for finding orthogonal eigenvectors of real symmetric tridiagonal is described. The method uses inverse iteration with repeated Modified Gram-Schmidt (MGS) reorthogonalization of the unconverged iterates for clustered eigenvalues. This approach is more parallelizable than reorthogonalizing against fully converged eigenvectors, as is done by LAPACK's current DSTEIN routine. The new method is found to provide accuracy and speed comparable to DSTEIN's and to have good parallel scalability even for matrices with large clusters of eigenvalues. We present al results for residual and orthogonality tests, plus timings on IBM RS/6000 (sequential) and Intel Touchstone DELTA (parallel) computers.

Fann, G.I.; Littlefield, R.J.

1993-03-01

263

Appendix E: Parallel Pascal development system  

NASA Technical Reports Server (NTRS)

The Parallel Pascal Development System enables Parallel Pascal programs to be developed and tested on a conventional computer. It consists of several system programs, including a Parallel Pascal to standard Pascal translator, and a library of Parallel Pascal subprograms. The library includes subprograms for using Parallel Pascal on a parallel system with a fixed degree of parallelism, such as the Massively Parallel Processor, to conveniently manipulate arrays which have dimensions than the hardware. Programs can be conveninetly tested with small sized arrays on the conventional computer before attempting to run on a parallel system.

1985-01-01

264

System Support for Implicitly Parallel Programming  

Microsoft Academic Search

Implicit parallelization involves developing parallel al- gorithms and applications in environments that pro- vide sequential semantics,e.g., the C programming lan- guage. System tools convert the parallel algorithms into a set of threads partitioned appropriately for a particular parallel machine organization. The result- ing parallel programs are easier and faster to develop, debug and maintain, because the programmer can re- quest

Matthew I. Frank

265

Parallel transport of long mean-free-path plasma along open magnetic field lines: Parallel heat flux  

SciTech Connect

In a long mean-free-path plasma where temperature anisotropy can be sustained, the parallel heat flux has two components with one associated with the parallel thermal energy and the other the perpendicular thermal energy. Due to the large deviation of the distribution function from local Maxwellian in an open field line plasma with low collisionality, the conventional perturbative calculation of the parallel heat flux closure in its local or non-local form is no longer applicable. Here, a non-perturbative calculation is presented for a collisionless plasma in a two-dimensional flux expander bounded by absorbing walls. Specifically, closures of previously unfamiliar form are obtained for ions and electrons, which relate two distinct components of the species parallel heat flux to the lower order fluid moments such as density, parallel flow, parallel and perpendicular temperatures, and the field quantities such as the magnetic field strength and the electrostatic potential. The plasma source and boundary condition at the absorbing wall enter explicitly in the closure calculation. Although the closure calculation does not take into account wave-particle interactions, the results based on passing orbits from steady-state collisionless drift-kinetic equation show remarkable agreement with fully kinetic-Maxwell simulations. As an example of the physical implications of the theory, the parallel heat flux closures are found to predict a surprising observation in the kinetic-Maxwell simulation of the 2D magnetic flux expander problem, where the parallel heat flux of the parallel thermal energy flows from low to high parallel temperature region.

Guo Zehua; Tang Xianzhu [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-06-15

266

Parallel fuzzy connected image segmentation on GPU  

PubMed Central

Purpose: Image segmentation techniques using fuzzy connectedness (FC) principles have shown their effectiveness in segmenting a variety of objects in several large applications. However, one challenge in these algorithms has been their excessive computational requirements when processing large image datasets. Nowadays, commodity graphics hardware provides a highly parallel computing environment. In this paper, the authors present a parallel fuzzy connected image segmentation algorithm implementation on NVIDIA’s compute unified device Architecture (cuda) platform for segmenting medical image data sets. Methods: In the FC algorithm, there are two major computational tasks: (i) computing the fuzzy affinity relations and (ii) computing the fuzzy connectedness relations. These two tasks are implemented as cuda kernels and executed on GPU. A dramatic improvement in speed for both tasks is achieved as a result. Results: Our experiments based on three data sets of small, medium, and large data size demonstrate the efficiency of the parallel algorithm, which achieves a speed-up factor of 24.4x, 18.1x, and 10.3x, correspondingly, for the three data sets on the NVIDIA Tesla C1060 over the implementation of the algorithm on CPU, and takes 0.25, 0.72, and 15.04 s, correspondingly, for the three data sets. Conclusions: The authors developed a parallel algorithm of the widely used fuzzy connected image segmentation method on the NVIDIA GPUs, which are far more cost- and speed-effective than both cluster of workstations and multiprocessing systems. A near-interactive speed of segmentation has been achieved, even for the large data set. PMID:21859037

Zhuge, Ying; Cao, Yong; Udupa, Jayaram K.; Miller, Robert W.

2011-01-01

267

Parallel Inversion of Sparse Matrices  

Microsoft Academic Search

This paper presents a parallel algorithm for obtaining the inverse of a large, nonsingular symmetric matrix A of dimension nxn. The inversion method proposed is based on the triangular factors of A. The task of obtaining the \\

Ramon Betancourt; Fernando L. Alvarado

1986-01-01

268

Software Logging under Speculative Parallelization  

E-print Network

Mar a Llaber az, V ctor Vi~nals, Lawrence Rauchwergerx, and Josep Torrellasy Universidad de Zaragoza://iacoma.cs.uiuc.edu x Texas A&M University rwerger@cs.tamu.edu Summary. Speculative parallelization aggressively runs

Garzarán, María Jesús

269

Parallelization of Stellar Atmosphere Codes  

NASA Astrophysics Data System (ADS)

Parallel computing has turned out as a enabling technology to solve complex physical systems. However, the transition from shared memory, vector computers to massively parallel, distributed memory systems and, recently, to hybrid systems poses new challenges to the scientist. We want to present a cook-book (with a very strong, personal bias) based on our experience with parallization of our code. Some of the general tools and communication libraries are discussed. Our approach includes a mixture of algorithm based, grid based and physical module based parallelization. The advantages, scalability and limitations of each are discussed at example calculations for supernovae. We hope to show that effective parallelization becomes easier with increasing complexity of the physical problem making stellar atmosphere beyond the classical assumptions very suitable.

Höflich, P.

2003-01-01

270

Debugging Serial and Parallel Codes  

NSDL National Science Digital Library

Introduction to debugger software. Serial debugging of array indexing, arguments mismatch, infinite loops, pointer misuse, and memory allocation. Parallel debugging of process count, shared memory, MPI I/O, collective communications, and OpenMP scope.

Ncsa

271

Designing and Building Parallel Programs  

NSDL National Science Digital Library

Designing and Building Parallel Programs [Online] is an innovative traditional print and online resource publishing project. It incorporates the content of a textbook published by Addison-Wesley into an evolving online resource.

272

Parallel Computing on Semidefinite Programs  

E-print Network

Apr 22, 2003 ... Mathematics and Computer Science Division ... Three criteria that influence the parallel scalability of the solver are ... these methods lack polynomial convergence in theory and sometimes exhibit slow convergence in practice.

2003-04-22

273

Spiral parallel magnetic resonance imaging.  

PubMed

Spiral k-space scanning is a rapid magnetic resonance imaging (MRI) technique that can provide an order of magnitude reduction in scan time compared to conventional spin warp techniques. Parallel imaging is another method for reducing scan time that exploits spatially varying radiofrequency (RF) coil sensitivities to reduce the amount of data required to reconstruct an image. Combining spiral scanning with parallel imaging provide a scan time reduction factor that is the product of the reduction factors for each of the techniques and thus can permit very rapid imaging. Image reconstruction for spiral parallel MRI is more involved than for spin warp parallel MRI and is an area of active research. Two techniques for performing this image reconstruction are PILS, a simple image-domain method that relies on localized coil sensitivities, and BOSCO, a method that is based on successive convolution operations in k-space. PMID:17946823

Meyer, Craig H; Hu, Peng

2006-01-01

274

Demonstrating Forces between Parallel Wires.  

ERIC Educational Resources Information Center

Describes a physics demonstration that dramatically illustrates the mutual repulsion (attraction) between parallel conductors using insulated copper wire, wooden dowels, a high direct current power supply, electrical tape, and an overhead projector. (WRM)

Baker, Blane

2000-01-01

275

Turbomachinery CFD on parallel computers  

NASA Technical Reports Server (NTRS)

The role of multistage turbomachinery simulation in the development of propulsion system models is discussed. Particularly, the need for simulations with higher fidelity and faster turnaround time is highlighted. It is shown how such fast simulations can be used in engineering-oriented environments. The use of parallel processing to achieve the required turnaround times is discussed. Current work by several researchers in this area is summarized. Parallel turbomachinery CFD research at the NASA Lewis Research Center is then highlighted. These efforts are focused on implementing the average-passage turbomachinery model on MIMD, distributed memory parallel computers. Performance results are given for inviscid, single blade row and viscous, multistage applications on several parallel computers, including networked workstations.

Blech, Richard A.; Milner, Edward J.; Quealy, Angela; Townsend, Scott E.

1992-01-01

276

Shifting the Parallel Programming Paradigm  

Microsoft Academic Search

Multicore computer architectures are now the standard for desktop computers, high-end servers and personal laptops. Due to the multicore shift in computer architecture, soft- ware engineers must write multithreaded programs to har- ness the resources of these parallel machines. Unfortunately, today's parallel programming techniques are difficult to rea- son about, highly error-prone and challenging to maintain for large-scale software. This

Justin E. Gottschlich; Dwight Y. Winkler; Mark W. Holmes; Jeremy G. Siek; Raytheon Compan

277

MCNPX RUNNING PARALLEL UNDER PVM  

Microsoft Academic Search

SUMMARY Gaps in the MCNPX code release 2.1.5 and release 2.2.3 were closed to enable running the code in multitasking mode on distributed memory parallel machines via the Parallel Virtual Machine (PVM) software. Performance tests were performed to check the runtime behavior of the code. These test show that the code scales well on small sized cluster machines, and provides

Franz X. Gallmeier; Phillip D. Ferguson

2008-01-01

278

Parallel stochastic systems biology in the cloud.  

PubMed

The stochastic modelling of biological systems, coupled with Monte Carlo simulation of models, is an increasingly popular technique in bioinformatics. The simulation-analysis workflow may result computationally expensive reducing the interactivity required in the model tuning. In this work, we advocate the high-level software design as a vehicle for building efficient and portable parallel simulators for the cloud. In particular, the Calculus of Wrapped Components (CWC) simulator for systems biology, which is designed according to the FastFlow pattern-based approach, is presented and discussed. Thanks to the FastFlow framework, the CWC simulator is designed as a high-level workflow that can simulate CWC models, merge simulation results and statistically analyse them in a single parallel workflow in the cloud. To improve interactivity, successive phases are pipelined in such a way that the workflow begins to output a stream of analysis results immediately after simulation is started. Performance and effectiveness of the CWC simulator are validated on the Amazon Elastic Compute Cloud. PMID:23780997

Aldinucci, Marco; Torquati, Massimo; Spampinato, Concetto; Drocco, Maurizio; Misale, Claudia; Calcagno, Cristina; Coppo, Mario

2014-09-01

279

AIAA 98-0692 MEASUREMENTS OF THE NEAR WAKE OF A ROTOR IN FORWARD FLIGHT  

E-print Network

describes initial measurements of the near wake of a 2-bladed teetering, untwisted, square- tipped rotor-wake of a helicopter rotor. Blade Vortex Interaction (BVI) noise is one of the biggest obstacles in community1 AIAA 98-0692 MEASUREMENTS OF THE NEAR WAKE OF A ROTOR IN FORWARD FLIGHT Raghav Mahalingam

280

VORTEX RING STATE PROTECTION FLIGHT CONTROL LAW Binh Dang-Vu  

E-print Network

main rotor noise is Blade-Vortex Interaction (BVI) noise [1]. BVI noise occurs mostly during low by the behaviour of the main rotor aerodynamics. The settling with power also referred to as Vortex Ring State (VRS/moderate speed descent flight, and sometimes in turning or manoeuvring flight, when the rotating blades pass

281

596 IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, VOL. 7, NO. 5, SEPTEMBER 1999 Feedback Attenuation and Adaptive Cancellation of  

E-print Network

frequency range, the main sources being the aerodynamic states of the main and tail rotors. Of these blade slap or bang. The main cause of this noise has been identified as blade vortex interaction (BVI to be achieved without appreciably altering the thrust produced by the main rotor, the other restriction being

Krstic, Miroslav

282

Issues with Multithreaded Parallelism on Multicore Architectures  

E-print Network

Issues with Multithreaded Parallelism on Multicore Architectures Marc Moreno Maza University of Western Ontario, London, Ontario (Canada) CS3101 (Moreno Maza) Issues with Multithreaded Parallelism on Multicore Architectures CS3101 1 / 35 #12;Plan (Moreno Maza) Issues with Multithreaded Parallelism

Moreno Maza, Marc

283

Parallel Implicit Algorithms for CFD  

NASA Technical Reports Server (NTRS)

The main goal of this project was efficient distributed parallel and workstation cluster implementations of Newton-Krylov-Schwarz (NKS) solvers for implicit Computational Fluid Dynamics (CFD.) "Newton" refers to a quadratically convergent nonlinear iteration using gradient information based on the true residual, "Krylov" to an inner linear iteration that accesses the Jacobian matrix only through highly parallelizable sparse matrix-vector products, and "Schwarz" to a domain decomposition form of preconditioning the inner Krylov iterations with primarily neighbor-only exchange of data between the processors. Prior experience has established that Newton-Krylov methods are competitive solvers in the CFD context and that Krylov-Schwarz methods port well to distributed memory computers. The combination of the techniques into Newton-Krylov-Schwarz was implemented on 2D and 3D unstructured Euler codes on the parallel testbeds that used to be at LaRC and on several other parallel computers operated by other agencies or made available by the vendors. Early implementations were made directly in Massively Parallel Integration (MPI) with parallel solvers we adapted from legacy NASA codes and enhanced for full NKS functionality. Later implementations were made in the framework of the PETSC library from Argonne National Laboratory, which now includes pseudo-transient continuation Newton-Krylov-Schwarz solver capability (as a result of demands we made upon PETSC during our early porting experiences). A secondary project pursued with funding from this contract was parallel implicit solvers in acoustics, specifically in the Helmholtz formulation. A 2D acoustic inverse problem has been solved in parallel within the PETSC framework.

Keyes, David E.

1998-01-01

284

Molecular dynamics in arbitrary geometries: Parallel evaluation of pair forces  

Microsoft Academic Search

A new algorithm for calculating intermolecular pair forces in molecular dynamics (MD) simulations on a distributed parallel computer is presented. The arbitrary interacting cells algorithm (AICA) is designed to operate on geometrical domains defined by an unstructured, arbitrary polyhedral mesh that has been spatially decomposed into irregular portions for parallelisation. It is intended for nano scale fluid mechanics simulation by

Graham B. Macpherson; Jason M. Reese

2008-01-01

285

Parallel plasma fluid turbulence calculations  

SciTech Connect

The study of plasma turbulence and transport is a complex problem of critical importance for fusion-relevant plasmas. To this day, the fluid treatment of plasma dynamics is the best approach to realistic physics at the high resolution required for certain experimentally relevant calculations. Core and edge turbulence in a magnetic fusion device have been modeled using state-of-the-art, nonlinear, three-dimensional, initial-value fluid and gyrofluid codes. Parallel implementation of these models on diverse platforms--vector parallel (National Energy Research Supercomputer Center`s CRAY Y-MP C90), massively parallel (Intel Paragon XP/S 35), and serial parallel (clusters of high-performance workstations using the Parallel Virtual Machine protocol)--offers a variety of paths to high resolution and significant improvements in real-time efficiency, each with its own advantages. The largest and most efficient calculations have been performed at the 200 Mword memory limit on the C90 in dedicated mode, where an overlap of 12 to 13 out of a maximum of 16 processors has been achieved with a gyrofluid model of core fluctuations. The richness of the physics captured by these calculations is commensurate with the increased resolution and efficiency and is limited only by the ingenuity brought to the analysis of the massive amounts of data generated.

Leboeuf, J.N.; Carreras, B.A.; Charlton, L.A.; Drake, J.B.; Lynch, V.E.; Newman, D.E.; Sidikman, K.L.; Spong, D.A.

1994-12-31

286

Parallelizing Timed Petri Net simulations  

NASA Technical Reports Server (NTRS)

The possibility of using parallel processing to accelerate the simulation of Timed Petri Nets (TPN's) was studied. It was recognized that complex system development tools often transform system descriptions into TPN's or TPN-like models, which are then simulated to obtain information about system behavior. Viewed this way, it was important that the parallelization of TPN's be as automatic as possible, to admit the possibility of the parallelization being embedded in the system design tool. Later years of the grant were devoted to examining the problem of joint performance and reliability analysis, to explore whether both types of analysis could be accomplished within a single framework. In this final report, the results of our studies are summarized. We believe that the problem of parallelizing TPN's automatically for MIMD architectures has been almost completely solved for a large and important class of problems. Our initial investigations into joint performance/reliability analysis are two-fold; it was shown that Monte Carlo simulation, with importance sampling, offers promise of joint analysis in the context of a single tool, and methods for the parallel simulation of general Continuous Time Markov Chains, a model framework within which joint performance/reliability models can be cast, were developed. However, very much more work is needed to determine the scope and generality of these approaches. The results obtained in our two studies, future directions for this type of work, and a list of publications are included.

Nicol, David M.

1993-01-01

287

Parallel integrated frame synchronizer chip  

NASA Technical Reports Server (NTRS)

A parallel integrated frame synchronizer which implements a sequential pipeline process wherein serial data in the form of telemetry data or weather satellite data enters the synchronizer by means of a front-end subsystem and passes to a parallel correlator subsystem or a weather satellite data processing subsystem. When in a CCSDS mode, data from the parallel correlator subsystem passes through a window subsystem, then to a data alignment subsystem and then to a bit transition density (BTD)/cyclical redundancy check (CRC) decoding subsystem. Data from the BTD/CRC decoding subsystem or data from the weather satellite data processing subsystem is then fed to an output subsystem where it is output from a data output port.

Ghuman, Parminder Singh (Inventor); Solomon, Jeffrey Michael (Inventor); Bennett, Toby Dennis (Inventor)

2000-01-01

288

Massively Parallel MRI Detector Arrays  

PubMed Central

Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called “ultimate” SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. PMID:23453758

Keil, Boris; Wald, Lawrence L

2013-01-01

289

Visualizing Parallel Computer System Performance  

NASA Technical Reports Server (NTRS)

Parallel computer systems are among the most complex of man's creations, making satisfactory performance characterization difficult. Despite this complexity, there are strong, indeed, almost irresistible, incentives to quantify parallel system performance using a single metric. The fallacy lies in succumbing to such temptations. A complete performance characterization requires not only an analysis of the system's constituent levels, it also requires both static and dynamic characterizations. Static or average behavior analysis may mask transients that dramatically alter system performance. Although the human visual system is remarkedly adept at interpreting and identifying anomalies in false color data, the importance of dynamic, visual scientific data presentation has only recently been recognized Large, complex parallel system pose equally vexing performance interpretation problems. Data from hardware and software performance monitors must be presented in ways that emphasize important events while eluding irrelevant details. Design approaches and tools for performance visualization are the subject of this paper.

Malony, Allen D.; Reed, Daniel A.

1988-01-01

290

Rochester checkers player: Multi-model parallel programming for animate vision. Technical report  

SciTech Connect

Animate vision systems couple computer vision and robotics to achieve robust and accurate vision, as well as other complex behavior. These systems combine low-level sensory processing and effector output with high-level cognitive planning - all computationally intensive tasks that can benefit from parallel processing. No single model of parallel programming is likely to serve for all tasks, however. Early vision algorithms are intensely data parallel, often utilizing fine-grain parallel computations that share an image, while cognition algorithms decompose naturally by function, often consisting of loosely-coupled, coarse-grain parallel units. A typical animate vision application will likely consist of many tasks, each of which may require a different parallel programming model, and all of which must cooperate to achieve the desired behavior. These multi-model programs require an underlying software system that not only supports several different models of parallel computation simultaneously, but which also allows tasks implemented in different models to interact.

Marsh, B.D.; Brown, C.M.; LeBlanc, T.J.; Scott, M.L.; Becker, T.G.

1991-06-01

291

Hybrid parallel programming with MPI and Unified Parallel C.  

SciTech Connect

The Message Passing Interface (MPI) is one of the most widely used programming models for parallel computing. However, the amount of memory available to an MPI process is limited by the amount of local memory within a compute node. Partitioned Global Address Space (PGAS) models such as Unified Parallel C (UPC) are growing in popularity because of their ability to provide a shared global address space that spans the memories of multiple compute nodes. However, taking advantage of UPC can require a large recoding effort for existing parallel applications. In this paper, we explore a new hybrid parallel programming model that combines MPI and UPC. This model allows MPI programmers incremental access to a greater amount of memory, enabling memory-constrained MPI codes to process larger data sets. In addition, the hybrid model offers UPC programmers an opportunity to create static UPC groups that are connected over MPI. As we demonstrate, the use of such groups can significantly improve the scalability of locality-constrained UPC codes. This paper presents a detailed description of the hybrid model and demonstrates its effectiveness in two applications: a random access benchmark and the Barnes-Hut cosmological simulation. Experimental results indicate that the hybrid model can greatly enhance performance; using hybrid UPC groups that span two cluster nodes, RA performance increases by a factor of 1.33 and using groups that span four cluster nodes, Barnes-Hut experiences a twofold speedup at the expense of a 2% increase in code size.

Dinan, J.; Balaji, P.; Lusk, E.; Sadayappan, P.; Thakur, R.; Mathematics and Computer Science; The Ohio State Univ.

2010-01-01

292

Parallel algorithms for mapping pipelined and parallel computations  

NASA Technical Reports Server (NTRS)

Many computational problems in image processing, signal processing, and scientific computing are naturally structured for either pipelined or parallel computation. When mapping such problems onto a parallel architecture it is often necessary to aggregate an obvious problem decomposition. Even in this context the general mapping problem is known to be computationally intractable, but recent advances have been made in identifying classes of problems and architectures for which optimal solutions can be found in polynomial time. Among these, the mapping of pipelined or parallel computations onto linear array, shared memory, and host-satellite systems figures prominently. This paper extends that work first by showing how to improve existing serial mapping algorithms. These improvements have significantly lower time and space complexities: in one case a published O(nm sup 3) time algorithm for mapping m modules onto n processors is reduced to an O(nm log m) time complexity, and its space requirements reduced from O(nm sup 2) to O(m). Run time complexity is further reduced with parallel mapping algorithms based on these improvements, which run on the architecture for which they create the mappings.

Nicol, David M.

1988-01-01

293

Constructions: Parallel Through A Point  

NSDL National Science Digital Library

After review of Construction Basics, the technique of constructing a parallel line through a point not on the line will be learned. Let's review the basics of Constructions in Geometry first: Constructions - General Rules Review of how to copy an angle is helpful; please review that here: Constructions: Copy a Line Segment and an Angle Now, using a paper, pencil, straight edge, and compass, you will learn how to construct a parallel through a point. A video demonstration is available to help you. (Windows Media ...

Neubert, Mrs.

2010-12-31

294

Benchmarking parallel image analysis systems  

NASA Astrophysics Data System (ADS)

Parallel image analysis systems are shown by the Abingdon Cross benchmark to excel over all other architectures both in terms of speed and cost performance. The Abingdon Cross benchmark is task specific so that the performance of the system under test can be optimized and adjusted to take full advantage of the system's capabilities. The authors have devised a new set of benchmarks for parallel image analysis systems consisting of individual tests of the following operations: (1) Point process, (2) integer convolution, (3) Fourier transform, (4) Boolean algebra, (5) histograming, (6) maximum ranking, (7) median ranking, (8) erosion! dilation, (9) memory to disk transfer, and (10) memory to display transfer.

Preston, Kendall, Jr.; Seigart, Carol

1990-07-01

295

Parallel counters for signed binary signals  

Microsoft Academic Search

A parallel counter is a combinational logic circuit that receives a set of binary count signals in parallel and determines the final count after some fixed delay. In this paper, a more general parallel counter is presented whose count inputs have three states (i.e. down, none, and up or, equivalently, -1, 0, and 1). Such parallel upldown counters find applications

Behrooz Parhami

1989-01-01

296

Determinacy and Repeatability of Parallel Program Schemata  

E-print Network

Determinacy and Repeatability of Parallel Program Schemata Jack B. Dennis Computer Science of asynchronous parallel compu- tations dates back to at least the 1960s. For example, the doctoral thesis of Earl, Texas Email: vsarkar@rice.edu Abstract--The concept of "determinism" of parallel programs and parallel

Kavi, Krishna

297

Exploiting heterogeneous parallelism on a multithreaded multiprocessor  

Microsoft Academic Search

This paper describes an integrated architecture, compiler, runtime, and operating system solution to exploiting heterogeneous parallelism. The architecture is a pipelined multi-threaded multiprocessor, enabling the execution of very fine (multiple operations within an instruction) to very coarse (multiple jobs) parallel activities. The compiler and runtime focus on managing parallelism within a job, while the operating system focuses on managing parallelism

Gail A. Alverson; Robert Alverson; David Callahan; Brian Koblenz; Allan Porterfield; Burton J. Smith

1992-01-01

298

Parallel object-oriented programming in SYMPAL  

Microsoft Academic Search

An object-oriented programming model in a parallel system is presented. It is designed for modelling, describing and solving a wide variety of AI problems. AI applications, in particular, deal with knowledge-bases and a lot of problems have parallel solutions. Therefore, while parallel computers are becoming widespread, there is a need for a rich language that enables the exploitation of parallelism

I. Danieli; S. Cohen

1988-01-01

299

File concepts for parallel I/O  

NASA Technical Reports Server (NTRS)

The subject of input/output (I/O) was often neglected in the design of parallel computer systems, although for many problems I/O rates will limit the speedup attainable. The I/O problem is addressed by considering the role of files in parallel systems. The notion of parallel files is introduced. Parallel files provide for concurrent access by multiple processes, and utilize parallelism in the I/O system to improve performance. Parallel files can also be used conventionally by sequential programs. A set of standard parallel file organizations is proposed, organizations are suggested, using multiple storage devices. Problem areas are also identified and discussed.

Crockett, Thomas W.

1989-01-01

300

Parallel active filter system implementation and design issues for utility interface of adjustable speed drive systems  

Microsoft Academic Search

This paper presents a parallel active filter system implementation for utility interface of an an adjustable speed drive air-conditioner chiller application to meet IEEE 519 recommended harmonic standards. Specifications of displacement power factor, efficiency, cost, size and packaging requirements with the rectifier front-end topology are used to determine the optimal active filter solution. Design issues and interaction of parallel active

S. Bhattacharya; T. M. Frank; D. M. Divan; B. Banerjee

1996-01-01

301

Web based parallel/distributed medical data mining using software agents  

SciTech Connect

This paper describes an experimental parallel/distributed data mining system PADMA (PArallel Data Mining Agents) that uses software agents for local data accessing and analysis and a web based interface for interactive data visualization. It also presents the results of applying PADMA for detecting patterns in unstructured texts of postmortem reports and laboratory test data for Hepatitis C patients.

Kargupta, H.; Stafford, B.; Hamzaoglu, I.

1997-12-31

302

Exploiting Parallelism to Accelerate Keyword Search On Deep-web Sources  

E-print Network

Exploiting Parallelism to Accelerate Keyword Search On Deep-web Sources Tantan Liu Fan Wang Gagan,wangfa,agrawal}@cse.ohio-state.edu Abstract. Increasingly, biological data is being shared over the deep web. Many biological queries can only that exploits parallelization for accelerating search over multiple deep web data sources. An interactive, two

Agrawal, Gagan

303

Parallel Programming Examples using MPI  

NSDL National Science Digital Library

Despite the rate at which computers have advanced in recent history, human imagination has advanced faster. Often greater computing power can be achieved by having multiple computers work together on a single problem. This tutorial discusses how Message Passing Interface (MPI) can be used to implement parallel programming solutions in a variety of cases.

Joiner, David; The Shodor Education Foundation, Inc.

304

Availability of a Parallel System  

Microsoft Academic Search

This paper considers a system which has two subsystems in parallel. One subsystem has a general life time and the other is 2-out-of-n:F. The first subsystem is given priority for repair. This paper discusses the availability of the system.

R. Ramanarayanan; K. Usha

1980-01-01

305

Parallel Programming with Declarative Ada  

E-print Network

, the Ada language, and Ada programming practice is given by Booch 2 . Explicit Parallelism in Ada Standard Declarative programming languages e.g., functional and logic pro- gramming languages are semantically elegant on a modern structured imperative language with single-assignment variables. Such a language combines

306

Portable Parallel Programming in HPC  

Microsoft Academic Search

HPC++ is a C++ library and language extension framework that is being developed by the HPC++ consortium as a standard model for portable parallel C++ programming. This paper provides a brief introduction to HPC++ style programming and outlines some of the unresolved issues

Peter H. Beckman; Dennis Gannon; Elizabeth Johnson

1996-01-01

307

The plane with parallel coordinates  

Microsoft Academic Search

By means ofParallel Coordinates planar “graphs” of multivariate relations are obtained. Certain properties of the relationship correspond tothe geometrical properties of its graph. On the plane a point ?? line duality with several interesting properties is induced. A new duality betweenbounded and unbounded convex sets and hstars (a generalization of hyperbolas) and between Convex Unions and Intersections is found. This

Alfred Inselberg

1985-01-01

308

Optical Interferometric Parallel Data Processor  

NASA Technical Reports Server (NTRS)

Image data processed faster than in present electronic systems. Optical parallel-processing system effectively calculates two-dimensional Fourier transforms in time required by light to travel from plane 1 to plane 8. Coherence interferometer at plane 4 splits light into parts that form double image at plane 6 if projection screen placed there.

Breckinridge, J. B.

1987-01-01

309

A rugged scalable parallel system  

Microsoft Academic Search

Tremendous strides are being made in the development of applications for scalable, parallel, high performance computing systems. One of the factors limiting further applications has been the lack of small, rugged, embeddable systems to support embedded airborne, shipboard, and landbased installations operating in severe environments. Litton Guidance and Control Systems, together with MasPar Computer Corporation, and supported by the Advanced

Alan L. Smeyne; John R. Nickolls

1995-01-01

310

Parallel Reduction Part I. Preliminaries  

E-print Network

-Reduce #12;4­2 BIG CPU, BIG DATA magine a square dartboard (Figure 4.1) with sides of length 1 the Parallel Java 2 Library class edu.rit.util.Random, rather than the standard Java class java.util.Random, for two reasons: my PRNG class is faster than Java's PRNG class; and my PRNG class has features useful

Kaminsky, Alan

311

Query Optimization for Parallel Execution  

Microsoft Academic Search

The decreasing cost of computing makes it economically viable to reduce the response time of decision support queries by using parallel execution to exploit inexpen- sive resources. This goal poses the following query op- timization problem: Mzntmzze response ttme subject to constraints on throughput, which we motivate as the dual of the traditional DBMS problem, We address this novel problem

Sumit Ganguly; Waqar Hasan; Ravi Krishnamurthy

1992-01-01

312

Ejs Parallel Plate Capacitor Model  

NSDL National Science Digital Library

The Ejs Parallel Plate Capacitor model displays a parallel-plate capacitor which consists of two identical metal plates, placed parallel to one another. The capacitor can be charged by connecting one plate to the positive terminal of a battery and the other plate to the negative terminal. The dielectric constant and the separation of the plates can be changed via sliders. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item. Ejs Parallel Plate Capacitor model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_capacitor.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Duffy, Andrew

2008-07-14

313

Parallel Processing and Information Retrieval.  

ERIC Educational Resources Information Center

This issue contains nine articles that provide an overview of trends and research in parallel information retrieval. Topics discussed include network design for text searching; the Connection Machine System; PThomas, an adaptive information retrieval system on the Connection Machine; algorithms for document clustering; and system architecture for…

Rasmussen, Edie M.; And Others

1991-01-01

314

Managing Checkpoints for Parallel Programs  

E-print Network

Managing Checkpoints for Parallel Programs Jim Pruyne and Miron Livny Department of Computer Sciences University of Wisconsin{Madison fpruyne, mirong@cs.wisc.edu Abstract Checkpointing is a valuable tool for any scheduling sys- tem to have. With the ability to checkpoint, schedulers are not locked

Feitelson, Dror

315

Managing Checkpoints for Parallel Programs  

E-print Network

Managing Checkpoints for Parallel Programs Jim Pruyne and Miron Livny Department of Computer Sciences University of Wisconsin--Madison fpruyne, mirong@cs.wisc.edu Abstract Checkpointing is a valuable tool for any scheduling sys­ tem to have. With the ability to checkpoint, schedulers are not locked

Wisconsin at Madison, University of

316

PARALLEL AND DISTRIBUTED SIMULATION SYSTEMS  

Microsoft Academic Search

Originating from basic research conducted in the 1970's and 1980's, the parallel and distributed simulation field has ma- tured over the last few decades. Today, operational systems have been fielded for applications such as military training, analysis of communication networks, and air traffic control systems, to mention a few. This tutorial gives an overview of technologies to distribute the execution

Richard M. Fujimoto

1999-01-01

317

Tutorial: Parallel Simulation on Supercomputers  

SciTech Connect

This tutorial introduces typical hardware and software characteristics of extant and emerging supercomputing platforms, and presents issues and solutions in executing large-scale parallel discrete event simulation scenarios on such high performance computing systems. Covered topics include synchronization, model organization, example applications, and observed performance from illustrative large-scale runs.

Perumalla, Kalyan S [ORNL

2012-01-01

318

Systematic parallel programming Jurgen Dingel  

E-print Network

Systematic parallel programming J¨urgen Dingel May 19, 2000 CMU­CS­99­172 School of Computer (DMSO) and the Semi­ conductor Research Corporation (SRC). The views and conclusions contained­level implementation from a trusted, high­level specification. The calculus thus helps structuring and documenting

319

Systematic parallel programming Jurgen Dingel  

E-print Network

Systematic parallel programming Jurgen Dingel May 19, 2000 CMU-CS-99-172 School of Computer Science and the Semi- conductor Research Corporation SRC. The views and conclusions contained in this document allows the stepwise formal derivation of an abstract, low-level implementation from a trusted, high

320

A mechanism for efficient debugging of parallel programs  

SciTech Connect

This paper addresses the design and implementation of an integrated debugging system for parallel programs running on shared memory multi-processors (SMMP). The authors describe the use of flowback analysis to provide information on causal relationships between events in a program's execution without re-executing the program for debugging. The authors introduce a mechanism called incremental tracing that, by using semantic analyses of the debugged program, makes the flowback analysis practical with only a small amount of trace generated during execution. The extend flowback analysis to apply to parallel programs and describe a method to detect race conditions in the interactions of the co-operating processes.

Miller, B.P.; Choi, J.D.

1988-01-01

321

Parallel aeroelastic computations for wing and wing-body configurations  

NASA Technical Reports Server (NTRS)

The objective of this research is to develop computationally efficient methods for solving fluid-structural interaction problems by directly coupling finite difference Euler/Navier-Stokes equations for fluids and finite element dynamics equations for structures on parallel computers. This capability will significantly impact many aerospace projects of national importance such as Advanced Subsonic Civil Transport (ASCT), where the structural stability margin becomes very critical at the transonic region. This research effort will have direct impact on the High Performance Computing and Communication (HPCC) Program of NASA in the area of parallel computing.

Byun, Chansup

1994-01-01

322

A Parallel Self--Consistent Field Code  

E-print Network

We describe a version of an algorithm for evolving self-gravitating collections of particles that should be nearly ideal for parallel architectures. Our method is derived from the ``self-consistent field'' (SCF) approach suggested previously by Clutton-Brock and others. Owing to the use of a global description of the gravitational field, the particles in an SCF simulation do not interact with one another directly, minimizing communications overhead between nodes in a parallel implementation. Ideal load-balancing is achieved since precisely the same number of operations are needed to compute the acceleration for each particle. Consequently, the SCF technique is perfectly scalable and the size of feasible applications will grow in simple proportion to advances in computational hardware. We describe an SCF code developed for and tested on a Connection Machine 5. Empirical tests demonstrate the efficient and scalable nature of the algorithm. Depending on the application, simulations with particle numbers in the range $N\\sim 10^7 - 10^{8.5}$ are now possible. Larger platforms should make simulations with billions of particles feasible in the near future. Specific astrophysical applications are discussed in the context of collisionless dynamics.

Lars Hernquist; Steinn Sigurdsson; Greg L. Bryan

1995-01-06

323

Parallel Simulation of Subsonic Fluid Dynamics on a Cluster of Workstations  

E-print Network

An effective approach of simulating fluid dynamics on a cluster of non- dedicated workstations is presented. The approach uses local interaction algorithms, small communication capacity, and automatic migration of parallel ...

Skordos, Panayotis A.

1995-12-01

324

Task parallelism and high-performance languages  

SciTech Connect

The definition of High Performance Fortran (HPF) is a significant event in the maturation of parallel computing: it represents the first parallel language that has gained widespread support from vendors and users. The subject of this paper is to incorporate support for task parallelism. The term task parallelism refers to the explicit creation of multiple threads of control, or tasks, which synchronize and communicate under programmer control. Task and data parallelism are complementary rather than competing programming models. While task parallelism is more general and can be used to implement algorithms that are not amenable to data-parallel solutions, many problems can benefit from a mixed approach, with for example a task-parallel coordination layer integrating multiple data-parallel computations. Other problems admit to both data- and task-parallel solutions, with the better solution depending on machine characteristics, compiler performance, or personal taste. For these reasons, we believe that a general-purpose high-performance language should integrate both task- and data-parallel constructs. The challenge is to do so in a way that provides the expressivity needed for applications, while preserving the flexibility and portability of a high-level language. In this paper, we examine and illustrate the considerations that motivate the use of task parallelism. We also describe one particular approach to task parallelism in Fortran, namely the Fortran M extensions. Finally, we contrast Fortran M with other proposed approaches and discuss the implications of this work for task parallelism and high-performance languages.

Foster, I.

1996-03-01

325

A Network Substrate for Peer-to-Peer Grid Computing beyond Embarrassingly Parallel Applications  

Microsoft Academic Search

Embarrassingly parallel grid applications require no inter-worker interaction. Thus, the underlying communication infrastructure is based on the simple but well understood client\\/server execution model. This is no longer sufficient if more demanding parallel applications that require true peer-to-peer interaction are to be deployed on grids. In this paper, we propose the industrial-strength eXtensible Messaging and Presence Protocol (XMPP) as a

Sven Schulz; Wolfgang Blochinger; Mathias Poths

2009-01-01

326

Method for resource control in parallel environments using program organization and run-time support  

NASA Technical Reports Server (NTRS)

A system and method for dynamic scheduling and allocation of resources to parallel applications during the course of their execution. By establishing well-defined interactions between an executing job and the parallel system, the system and method support dynamic reconfiguration of processor partitions, dynamic distribution and redistribution of data, communication among cooperating applications, and various other monitoring actions. The interactions occur only at specific points in the execution of the program where the aforementioned operations can be performed efficiently.

Ekanadham, Kattamuri (Inventor); Moreira, Jose Eduardo (Inventor); Naik, Vijay Krishnarao (Inventor)

1999-01-01

327

Method for resource control in parallel environments using program organization and run-time support  

NASA Technical Reports Server (NTRS)

A system and method for dynamic scheduling and allocation of resources to parallel applications during the course of their execution. By establishing well-defined interactions between an executing job and the parallel system, the system and method support dynamic reconfiguration of processor partitions, dynamic distribution and redistribution of data, communication among cooperating applications, and various other monitoring actions. The interactions occur only at specific points in the execution of the program where the aforementioned operations can be performed efficiently.

Ekanadham, Kattamuri (Inventor); Moreira, Jose Eduardo (Inventor); Naik, Vijay Krishnarao (Inventor)

2001-01-01

328

Parallel TREE code for two-component ultracold plasma analysis  

E-print Network

The TREE method has been widely used for long-range interaction {\\it N}-body problems. We have developed a parallel TREE code for two-component classical plasmas with open boundary conditions and highly non-uniform charge distributions. The program efficiently handles millions of particles evolved over long relaxation times requiring millions of time steps. Appropriate domain decomposition and dynamic data management were employed, and large-scale parallel processing was achieved using an intermediate level of granularity of domain decomposition and ghost TREE communication. Even though the computational load is not fully distributed in fine grains, high parallel efficiency was achieved for ultracold plasma systems of charged particles. As an application, we performed simulations of an ultracold neutral plasma with a half million particles and a half million time steps. For the long temporal trajectories of relaxation between heavy ions and light electrons, large configurations of ultracold plasmas can now be...

Jeon, Byoungseon; Collins, Lee A; Grønbech-Jensen, Niels

2007-01-01

329

A Parallel Quantum Computer Simulator  

E-print Network

A Quantum Computer is a new type of computer which can efficiently solve complex problems such as prime factorization. A quantum computer threatens the security of public key encryption systems because these systems rely on the fact that prime factorization is computationally difficult. Errors limit the effectiveness of quantum computers. Because of the exponential nature of quantum com puters, simulating the effect of errors on them requires a vast amount of processing and memory resources. In this paper we describe a parallel simulator which accesses the feasibility of quantum computers. We also derive and validate an analytical model of execution time for the simulator, which shows that parallel quantum computer simulation is very scalable.

Kevin M. Obenland; Alvin M. Despain

1998-04-16

330

Parallel multiplex laser feedback interferometry  

SciTech Connect

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2? simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimental results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 ?m.

Zhang, Song; Tan, Yidong; Zhang, Shulian, E-mail: zsl-dpi@mail.tsinghua.edu.cn [State Key Laboratory of Precision Measurements, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)] [State Key Laboratory of Precision Measurements, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)

2013-12-15

331

Instruction-level parallel processing.  

PubMed

The performance of microprocessors has increased steadily over the past 20 years at a rate of about 50% per year. This is the cumulative result of architectural improvements as well as increases in circuit speed. Moreover, this improvement has been obtained in a transparent fashion, that is, without requiring programmers to rethink their algorithms and programs, thereby enabling the tremendous proliferation of computers that we see today. To continue this performance growth, microprocessor designers have incorporated instruction-level parallelism (ILP) into new designs. ILP utilizes the parallel execution ofthe lowest level computer operations-adds, multiplies, loads, and so on-to increase performance transparently. The use of ILP promises to make possible, within the next few years, microprocessors whose performance is many times that of a CRAY-IS. This article provides an overview of ILP, with an emphasis on ILP architectures-superscalar, VLIW, and dataflow processors-and the compiler techniques necessary to make ILP work well. PMID:17831442

Fisher, J A; Rau, R

1991-09-13

332

Parallel processing spacecraft communication system  

NASA Technical Reports Server (NTRS)

An uplink controlling assembly speeds data processing using a special parallel codeblock technique. A correct start sequence initiates processing of a frame. Two possible start sequences can be used; and the one which is used determines whether data polarity is inverted or non-inverted. Processing continues until uncorrectable errors are found. The frame ends by intentionally sending a block with an uncorrectable error. Each of the codeblocks in the frame has a channel ID. Each channel ID can be separately processed in parallel. This obviates the problem of waiting for error correction processing. If that channel number is zero, however, it indicates that the frame of data represents a critical command only. That data is handled in a special way, independent of the software. Otherwise, the processed data further handled using special double buffering techniques to avoid problems from overrun. When overrun does occur, the system takes action to lose only the oldest data.

Bolotin, Gary S. (Inventor); Donaldson, James A. (Inventor); Luong, Huy H. (Inventor); Wood, Steven H. (Inventor)

1998-01-01

333

Parallel supercomputing with commodity components  

SciTech Connect

We have implemented a parallel computer architecture based entirely upon commodity personal computer components. Using 16 Intel Pentium Pro microprocessors and switched fast ethernet as a communication fabric, we have obtained sustained performance on scientific applications in excess of one Gigaflop. During one production astrophysics treecode simulation, we performed 1.2 x 10{sup 15} floating point operations (1.2 Petaflops) over a three week period, with one phase of that simulation running continuously for two weeks without interruption. We report on a variety of disk, memory and network benchmarks. We also present results from the NAS parallel benchmark suite, which indicate that this architecture is competitive with current commercial architectures. In addition, we describe some software written to support efficient message passing, as well as a Linux device driver interface to the Pentium hardware performance monitoring registers.

Warren, M.S.; Goda, M.P. [Los Alamos National Lab., NM (United States); Becker, D.J. [Goddard Space Flight Center, Greenbelt, MD (United States)] [and others

1997-09-01

334

Parallel multiplex laser feedback interferometry  

NASA Astrophysics Data System (ADS)

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2? simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimental results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 ?m.

Zhang, Song; Tan, Yidong; Zhang, Shulian

2013-12-01

335

Dynamic Scheduling on Parallel Machines  

Microsoft Academic Search

The problem of online job scheduling on various parallel architectures is studied. An O((log log n)1\\/2 )-competitive algorithm for online dynamic scheduling on an n ×n mesh is given. It is proved that this algorithm is optimal up to a constant factor. The algorithm is not greedy, and the lower bound proof shows that no greedy-like algorithm can be very

Anja Feldmann; Jiri Sgall; Shang-hua Teng

1991-01-01

336

Universal schemes for parallel communication  

Microsoft Academic Search

In this paper we isolate a combinatorial problem that, we believe, lies at the heart of this question and provide some encouragingly positive solutions to it. We show that there exists an N-processor realistic computer that can simulate arbitrary idealistic N-processor parallel computations with only a factor of O(log N) loss of runtime efficiency. The main innovation is an O(log

Leslie G. Valiant; Gordon J. Brebner

1981-01-01

337

Parallel strategies for SAR processing  

NASA Astrophysics Data System (ADS)

This article proposes a series of strategies for improving the computer process of the Synthetic Aperture Radar (SAR) signal treatment, following the three usual lines of action to speed up the execution of any computer program. On the one hand, it is studied the optimization of both, the data structures and the application architecture used on it. On the other hand it is considered a hardware improvement. For the former, they are studied both, the usually employed SAR process data structures, proposing the use of parallel ones and the way the parallelization of the algorithms employed on the process is implemented. Besides, the parallel application architecture classifies processes between fine/coarse grain. These are assigned to individual processors or separated in a division among processors, all of them in their corresponding architectures. For the latter, it is studied the hardware employed on the computer parallel process used in the SAR handling. The improvement here refers to several kinds of platforms in which the SAR process is implemented, shared memory multicomputers, and distributed memory multiprocessors. A comparison between them gives us some guidelines to follow in order to get a maximum throughput with a minimum latency and a maximum effectiveness with a minimum cost, all together with a limited complexness. It is concluded and described, that the approach consisting of the processing of the algorithms in a GNU/Linux environment, together with a Beowulf cluster platform offers, under certain conditions, the best compromise between performance and cost, and promises the major development in the future for the Synthetic Aperture Radar computer power thirsty applications in the next years.

Segoviano, Jesus A.

2004-12-01

338

Fully Parallel Stochastic LDPC Decoders  

Microsoft Academic Search

Stochastic decoding is a new approach to iterative decoding on graphs. This paper presents a hardware architecture for fully parallel stochastic low-density parity-check (LDPC) de- coders. To obtain the characteristics of the proposed architecture, we apply this architecture to decode an irregular state-of-the-art (1056,528) LDPC code on a Xilinx Virtex-4 LX200 field-pro- grammable gate-array (FPGA) device. The implemented decoder achieves

Saeed Sharifi Tehrani; Shie Mannor; Warren J. Gross

2008-01-01

339

Middle Path Coarse Grain Parallelization  

E-print Network

Backend OpenMP Fortran OpenMP Backend MPI Fortran MPI Backend ½ �� � BPA RB SB Program Near fine grain layer 3rd layer Near fine grain parallelism in loop body BPA RB SB BPA RB SB BPA RB SB BPA RB SB BPA RB SB BPA RB SB ¾ ¾º½º½ � � Á � � � ¾ Data Dependency Extended Contorol Dependency Conditional Branch

Kasahara, Hironori

340

IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, VOL. 9, NO. 3, MARCH 1998 283 Parallel Computation  

E-print Network

performance demonstrates that parallel computational methods can significantly reduce the computational time developed parallel methods to reduce the time required to perform two com- putationally intensive analyses: homologous sequence searching and multiple sequence alignment. Our parallel searching method reduces

341

Highly parallel sparse Cholesky factorization  

NASA Technical Reports Server (NTRS)

Several fine grained parallel algorithms were developed and compared to compute the Cholesky factorization of a sparse matrix. The experimental implementations are on the Connection Machine, a distributed memory SIMD machine whose programming model conceptually supplies one processor per data element. In contrast to special purpose algorithms in which the matrix structure conforms to the connection structure of the machine, the focus is on matrices with arbitrary sparsity structure. The most promising algorithm is one whose inner loop performs several dense factorizations simultaneously on a 2-D grid of processors. Virtually any massively parallel dense factorization algorithm can be used as the key subroutine. The sparse code attains execution rates comparable to those of the dense subroutine. Although at present architectural limitations prevent the dense factorization from realizing its potential efficiency, it is concluded that a regular data parallel architecture can be used efficiently to solve arbitrarily structured sparse problems. A performance model is also presented and it is used to analyze the algorithms.

Gilbert, John R.; Schreiber, Robert

1990-01-01

342

STALK : an interactive virtual molecular docking system.  

SciTech Connect

Several recent technologies-genetic algorithms, parallel and distributed computing, virtual reality, and high-speed networking-underlie a new approach to the computational study of how biomolecules interact or 'dock' together. With the Stalk system, a user in a virtual reality environment can interact with a genetic algorithm running on a parallel computer to help in the search for likely geometric configurations.

Levine, D.; Facello, M.; Hallstrom, P.; Reeder, G.; Walenz, B.; Stevens, F.; Univ. of Illinois

1997-04-01

343

Parallel processing of atmospheric chemistry calculations: Preliminary considerations  

SciTech Connect

Global climate calculations are already saturating the class modern vector supercomputers with only a few central processing units. Increased resolution and inclusion of routines to deal with biogeochemical portions of the terrestrial climate system will soon demand massively parallel approaches. The atmospheric photochemistry ensemble is intimately linked to climate through the trace greenhouse gases ozone and methane and modules for representing it are being attached to global three dimensional transport and GCM frameworks. Atmospheric kinetics involve dozens of highly interactive tracers and so will accentuate the need for parallel processing of earth system simulations. In the present text we lay some of the groundwork for addition of atmospheric kinetics packages to GCM and global scale atmospheric models on multiply parallel computers. The discussion is tailored for consumption by the photochemical modelling community. After a review of numerical atmospheric chemistry methods, we examine how kinetics can be implemented on a parallel computer. We concentrate especially on data layout and flexibility and how these can be implemented in various programming models. We conclude that chemistry can be implemented rather easily within existing frameworks of several parallel atmospheric models. However, memory limitations may preclude high resolution studies of global chemistry.

Elliott, S.; Jones, P.

1995-01-01

344

NWChem: scalable parallel computational chemistry  

SciTech Connect

NWChem is a general purpose computational chemistry code specifically designed to run on distributed memory parallel computers. The core functionality of the code focuses on molecular dynamics, Hartree-Fock and density functional theory methods for both plane-wave basis sets as well as Gaussian basis sets, tensor contraction engine based coupled cluster capabilities and combined quantum mechanics/molecular mechanics descriptions. It was realized from the beginning that scalable implementations of these methods required a programming paradigm inherently different from what message passing approaches could offer. In response a global address space library, the Global Array Toolkit, was developed. The programming model it offers is based on using predominantly one-sided communication. This model underpins most of the functionality in NWChem and the power of it is exemplified by the fact that the code scales to tens of thousands of processors. In this paper the core capabilities of NWChem are described as well as their implementation to achieve an efficient computational chemistry code with high parallel scalability. NWChem is a modern, open source, computational chemistry code1 specifically designed for large scale parallel applications2. To meet the challenges of developing efficient, scalable and portable programs of this nature a particular code design was adopted. This code design involved two main features. First of all, the code is build up in a modular fashion so that a large variety of functionality can be integrated easily. Secondly, to facilitate writing complex parallel algorithms the Global Array toolkit was developed. This toolkit allows one to write parallel applications in a shared memory like approach, but offers additional mechanisms to exploit data locality to lower communication overheads. This framework has proven to be very successful in computational chemistry but is applicable to any engineering domain. Within the context created by the features above NWChem has grown into a general purpose computational chemistry code that supports a wide variety of energy expressions and capabilities to calculate properties based there upon. The main energy expressions are classical mechanics force fields, Hartree-Fock and DFT both for finite systems and condensed phase systems, coupled cluster, as well as QM/MM. For most energy expressions single point calculations, geometry optimizations, excited states, and other properties are available. Below we briefly discuss each of the main energy expressions and the critical points involved in scalable implementations thereof.

van Dam, Hubertus JJ; De Jong, Wibe A.; Bylaska, Eric J.; Govind, Niranjan; Kowalski, Karol; Straatsma, TP; Valiev, Marat

2011-11-01

345

GPU-based simulation of the long-range Potts model via parallel tempering  

NASA Astrophysics Data System (ADS)

We discuss the efficiency of parallelization on graphical processing units (GPUs) for the simulation of the one-dimensional Potts model with long-range interactions via parallel tempering. We investigate the behavior of some thermodynamic properties, such as equilibrium energy and magnetization, critical temperatures as well as the separation between the first- and second-order regimes. By implementing multispin coding techniques and an efficient parallelization of the interaction energy computation among threads, the GPU-accelerated approach reached speedup factors of up to 37.

Boer, Attila

2014-07-01

346

Parallel ecological networks in ecosystems  

PubMed Central

In ecosystems, species interact with other species directly and through abiotic factors in multiple ways, often forming complex networks of various types of ecological interaction. Out of this suite of interactions, predator–prey interactions have received most attention. The resulting food webs, however, will always operate simultaneously with networks based on other types of ecological interaction, such as through the activities of ecosystem engineers or mutualistic interactions. Little is known about how to classify, organize and quantify these other ecological networks and their mutual interplay. The aim of this paper is to provide new and testable ideas on how to understand and model ecosystems in which many different types of ecological interaction operate simultaneously. We approach this problem by first identifying six main types of interaction that operate within ecosystems, of which food web interactions are one. Then, we propose that food webs are structured among two main axes of organization: a vertical (classic) axis representing trophic position and a new horizontal ‘ecological stoichiometry’ axis representing decreasing palatability of plant parts and detritus for herbivores and detrivores and slower turnover times. The usefulness of these new ideas is then explored with three very different ecosystems as test cases: temperate intertidal mudflats; temperate short grass prairie; and tropical savannah. PMID:19451126

Olff, Han; Alonso, David; Berg, Matty P.; Eriksson, B. Klemens; Loreau, Michel; Piersma, Theunis; Rooney, Neil

2009-01-01

347

Asynchronous Migration in Parallel Genetic Programming  

E-print Network

Asynchronous Migration in Parallel Genetic Programming Shisanu Tongchim and Prabhas Chongstitvatana, every subpopulation was migrated between processors using a fully connected topology. The parallel MPI as a message passing library. In the first stage of the implementation, the migration

Fernandez, Thomas

348

Testing Techniques for Parallel Software (TTPS).  

National Technical Information Service (NTIS)

The Testing Techniques for Parallel Software (TTPS) project was conducted by Optimization Technology, Inc. for Rome Laboratory. The purpose was to investigate and implement candidate parallel software testing techniques to improve the quality and reliabil...

R. C. Cox

1996-01-01

349

Parallel Coupled Micro-Macro Actuators  

E-print Network

This thesis presents a new actuator system consisting of a micro-actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the Parallel Coupled Micro-Macro Actuator, or PaCMMA. ...

Morrell, John Bryant

1996-01-01

350

On-the-fly pipeline parallelism  

E-print Network

Pipeline parallelism organizes a parallel program as a linear sequence of s stages. Each stage processes elements of a data stream, passing each processed data element to the next stage, and then taking on a new element ...

Lee, I-Ting Angelina

351

Instrumentation for parallel magnetic resonance imaging  

E-print Network

of arrays of sensors. In parallelization, multiple MR scanners (or multiple sensors) are used to collect images from different samples simultaneously. This allows for an increase in the throughput, not the inherent speed, of the MR experiment. Parallel...

Brown, David Gerald

2007-04-25

352

Adaptively Parallel Processor Allocation for Cilk Jobs  

E-print Network

The problem of allocating processor resources fairly and efficiently to parallel jobs has been studied extensively in the past. Most of this work, however, assumes that the instantaneous parallelism of the jobs is known ...

Sen, Siddhartha

353

High performance parallel algorithms for incompressible flows  

E-print Network

Object-Oriented design for the algorithms and its parallel implementation in multi-threading and multi-processing environments is presented. Inexpensive parallel matrix-vector products using bounded buffers for inter-processor communication are suggested...

Sambavaram, Sreekanth Reddy

2012-06-07

354

Parallel machine architecture and compiler design facilities  

NASA Technical Reports Server (NTRS)

The objective is to provide an integrated simulation environment for studying and evaluating various issues in designing parallel systems, including machine architectures, parallelizing compiler techniques, and parallel algorithms. The status of Delta project (which objective is to provide a facility to allow rapid prototyping of parallelized compilers that can target toward different machine architectures) is summarized. Included are the surveys of the program manipulation tools developed, the environmental software supporting Delta, and the compiler research projects in which Delta has played a role.

Kuck, David J.; Yew, Pen-Chung; Padua, David; Sameh, Ahmed; Veidenbaum, Alex

1990-01-01

355

Overview – Parallel Computing: Numerics, Applications, and Trends  

Microsoft Academic Search

This book is intended for researchers and practitioners as a foundation for modern parallel computing with several of its\\u000a important parallel applications, and also for students as a basic or supplementary book to accompany advanced courses on parallel\\u000a computing. Fifteen chapters cover the most important issues in parallel computing, from basic principles through more complex\\u000a theoretical problems and applications, together

Marián Vajteršic; Peter Zinterhof; Roman Trobec

356

Hybrid Parallel Programming on HPC Platforms  

Microsoft Academic Search

Summary Most HPC systems are clusters of shared memory nodes. Parallel programming must combine the distributed mem- ory parallelization on the node inter-connect with the shared memory parallelization inside of each node. Various hybrid MPI+OpenMP programming models are compared with pure MPI. Benchmark results of several platforms are presented. This paper analyzes the strength and weakness of several parallel programming

Rolf Rabenseifner

2003-01-01

357

Integrating Parallelizing Compilation Technologies for SMP Clusters  

Microsoft Academic Search

In this paper, a source to source parallelizing complier system, AutoPar, is presentd. The system transforms FORTRAN programs to multi-level hybrid MPI\\/OpenMP parallel programs. Integrated parallel optimizing technologies are utilized extensively to derive an effective program decomposition in the whole program scope. Other features such as synchronization optimization and communication optimization improve the performance scalability of the generated parallel programs,

Xiao-Bing Feng; Li Chen; Yi-Ran Wang; An Xiao-mi; Lin Ma; Chun-lei Sang; Zhao-Qing Zhang

2005-01-01

358

Automatic Multilevel Parallelization Using OpenMP  

NASA Technical Reports Server (NTRS)

In this paper we describe the extension of the CAPO (CAPtools (Computer Aided Parallelization Toolkit) OpenMP) parallelization support tool to support multilevel parallelism based on OpenMP directives. CAPO generates OpenMP directives with extensions supported by the NanosCompiler to allow for directive nesting and definition of thread groups. We report some results for several benchmark codes and one full application that have been parallelized using our system.

Jin, Hao-Qiang; Jost, Gabriele; Yan, Jerry; Ayguade, Eduard; Gonzalez, Marc; Martorell, Xavier; Biegel, Bryan (Technical Monitor)

2002-01-01

359

Collective Interaction of a Compressible Periodic Parallel Jet Flow  

NASA Technical Reports Server (NTRS)

A linear instability model for multiple spatially periodic supersonic rectangular jets is solved using Floquet-Bloch theory. The disturbance environment is investigated using a two dimensional perturbation of a mean flow. For all cases large temporal growth rates are found. This work is motivated by an increase in mixing found in experimental measurements of spatially periodic supersonic rectangular jets with phase-locked screech. The results obtained in this paper suggests that phase-locked screech or edge tones may produce correlated spatially periodic jet flow downstream of the nozzles which creates a large span wise multi-nozzle region where a disturbance can propagate. The large temporal growth rates for eddies obtained by model calculation herein are related to the increased mixing since eddies are the primary mechanism that transfer energy from the mean flow to the large turbulent structures. Calculations of growth rates are presented for a range of Mach numbers and nozzle spacings corresponding to experimental test conditions where screech synchronized phase locking was observed. The model may be of significant scientific and engineering value in the quest to understand and construct supersonic mixer-ejector nozzles which provide increased mixing and reduced noise.

Miles, Jeffrey Hilton

1997-01-01

360

Social interaction shapes babbling: Testing parallels between birdsong and speech  

E-print Network

a mechanism of phonological development in human infants that is based on social shaping, a selective learning of development? Previous com- parisons (1, 3) focused on maturation of motor and memory abilities and concluded (received for review August 22, 2002) Birdsong is considered a model of human speech development

Yu, Chen

361

Hydrogen and electricity: Parallels, interactions,and convergence  

E-print Network

water split- ting (electrolysis), for hydrogen storage andhydrogen and oxygen combine to form water and the electrolysiselectrolysis to compete economically with fossil- based hydrogen production, low cost electricity is essential. Electrolysis of water

Yang, Christopher

2008-01-01

362

Parallel expression profiling of barley-stem rust interactions.  

PubMed

The dominant barley stem rust resistance gene Rpg1 confers resistance to many but not all pathotypes of the stem rust fungus Puccinia graminis f. sp. tritici (Pgt). Transformation of Rpg1 into susceptible cultivar Golden Promise rendered the transgenic plants resistant to Pgt pathotype MCC but not to Pgt pathotype QCC. Our objective was to identify genes that are induced/repressed during the early stages of pathogen infection to elucidate the molecular mechanisms and role of Rpg1 in defense. A messenger ribonucleic acid expression analysis using the 22K Barley1 GeneChip was conducted in all pair-wise combinations of two isolines (cv. Golden Promise and Rpg1 transgenic line G02-448F-3R) and two Pgt pathotypes (MCC and QCC) across six time points. Analysis showed that a total of 34 probe sets exhibited expression pattern differences between Golden Promise (susceptible) and G02-448F-3R (resistant) infected with Pgt-MCC. A total of 14 probe sets exhibited expression pattern differences between Pgt-MCC (avirulent) and Pgt-QCC (virulent) inoculated onto G02-448F-3R. These differentially expressed genes were activated during the early infection process, before the hypersensitive response or fungal growth inhibition occurred. Our analysis provides a list of candidate signaling components, which can be analyzed for function in Rpg1-mediated disease resistance. PMID:18196301

Zhang, Ling; Castell-Miller, Claudia; Dahl, Stephanie; Steffenson, Brian; Kleinhofs, Andris

2008-08-01

363

Parallel expression profiling of barley–stem rust interactions  

Microsoft Academic Search

The dominant barley stem rust resistance gene Rpg1 confers resistance to many but not all pathotypes of the stem rust fungus Puccinia graminis f. sp. tritici (Pgt). Transformation of Rpg1 into susceptible cultivar Golden Promise rendered the transgenic plants resistant to Pgt pathotype MCC but not to Pgt pathotype QCC. Our objective was to identify genes that are induced\\/repressed during

Ling Zhang; Claudia Castell-Miller; Stephanie Dahl; Brian Steffenson; Andris Kleinhofs

2008-01-01

364

Exchange Interactions in Solid HELIUM3 on a Parallel Computer  

Microsoft Academic Search

We have developed a method of calculating the Gruneisen parameter, gamma equiv partialln J\\/ partial ln v (J - exchange splitting; v - molar volume), for energy splitting that are due to atoms exchanging lattice sites in fermionic systems for which the exchange splittings are small compared with the lattice kinetic and potential energies. The method involves making two separate

Sean Macauley Callahan

1989-01-01

365

EUROPA Parallel C++ Version 2.1  

E-print Network

EUROPA Parallel C++ Version 2.1 The EUROPA Working Group on Parallel C++ Architecture SIG July 10.Roberts@cs.ucl.ac.uk), Winder Russel (R.Winder@dcs.kcl.ac.uk). Abstract This paper presents the deønition of EUROPA: a framework within which parallel C++ environments can be developed and standardised. EUROPA (also called EC++) sets

Caromel, Denis

366

Identifying, Quantifying, Extracting and Enhancing Implicit Parallelism  

ERIC Educational Resources Information Center

The shift of the microprocessor industry towards multicore architectures has placed a huge burden on the programmers by requiring explicit parallelization for performance. Implicit Parallelization is an alternative that could ease the burden on programmers by parallelizing applications "under the covers" while maintaining sequential semantics…

Agarwal, Mayank

2009-01-01

367

Compiling parallel programs by optimizing performance  

Microsoft Academic Search

This paper describes how Crystal, a language based on familiar mathematical notation and lambda calculus, addresses the issues of programmability and performance for parallel supercomputers. Some scientifc programmers and theoreticians may ask, “What is new about Crystal?” or “How is it different from existing functional languages?” The answers lie in its model of parallel computation and a theory of parallel

Marina Chen; Young-Il Choo; Jingke Li

1988-01-01

368

Parallelism generics for Ada 2005 and beyond  

Microsoft Academic Search

The Ada programming language is seemingly well-positioned to take advantage of emerging multi-core technologies. While it has always been possible to write parallel algorithms in Ada, there are certain classes of problems however, where the level of effort to write parallel algorithms outweighs the ease and simplicity of a sequential approach. This can result in lost opportunities for parallelism and

Brad J. Moore

2010-01-01

369

Agent communication based SAR image parallel processing  

Microsoft Academic Search

Airborne SAR remote sensing image has the characteristic of large data volume and computation burden, so the processing needs very large computer memory and stronger computation ability. Based on the introduction of the SAR image processing procedure, we study the SAR image processing using computer parallel computation technology. The parallel processing mechanism is based on the parallel computer cluster operation

Tianhe Chi; Xin Zhang; Hongqiao Wu; Jinyun Fang

2003-01-01

370

GPU Massively Parallel Part I. Preliminaries  

E-print Network

Chapter 21 GPU Massively Parallel Part I. Preliminaries Part II. Tightly Coupled Multicore Part III. Loosely Coupled Cluster Part IV. GPU Acceleration Chapter 21. GPU Massively Parallel Chapter 22. GPU Parallel Reduction Chapter 23. Multi-GPU Programming Chapter 24. GPU Sequential Dependencies

Kaminsky, Alan

371

Hyperdimensional Data Analysis Using Parallel Coordinates  

Microsoft Academic Search

This article presents the basic results of using the parallel coordinate representation as a high-dimensional data analysis tool. Several alternatives are reviewed. The basic algorithm for parallel coordinates is laid out and a discussion of its properties as a projective transformation is given. Several duality results are discussed along with their interpretations as data analysis tools. Permutations of the parallel

Edward J. Wegman

1990-01-01

372

Class Overview: 1. Concepts of parallel structures  

E-print Network

data parallelism ! Unlimited / Fixed / Scalable Parallelism 5. Working groups discussion Concepts memory) by changing (iii): ! ! sum2 = b + 1; ! 01/31/2011 ! Parallel & Distributed Computing Class Notes. Locality: ! Temporal locality: references to memory clustered in time. ! ! For example: in count3s

Iamnitchi, Adriana

373

Experimental Study of Multipopulation Parallel Genetic Programming.  

E-print Network

, there is no doubt about the nature of the Parallel Genetic Programming (PGP) algorithm. All authors agree studies have reported the efficiency of parallel Genetic Algorithms and have studied the relationshipExperimental Study of Multipopulation Parallel Genetic Programming. Fernández F.1 , Tomassini M. 2

Fernandez, Thomas

374

Generating random numbers in parallel Mark Hoemmen  

E-print Network

the random numbers in parallel too. We won't make you implement all of this yourself in HW 1, but we do think to parallelize random number generation yourself some time. We'll begin by explaining what we mean by "random random numbers in some of your parallel applications in the future, and you may very well have

California at Berkeley, University of

375

Issues with Multithreaded Parallelism on Multicore Architectures  

E-print Network

Issues with Multithreaded Parallelism on Multicore Architectures Marc Moreno Maza University of Western Ontario, London, Ontario (Canada) CS3101 (Moreno Maza) Issues with Multithreaded Parallelism on Multicore Architectures CS3101 1 / 35 Plan (Moreno Maza) Issues with Multithreaded Parallelism on Multicore

Moreno Maza, Marc

376

Happe Honeywell Associative Parallel Processing Ensemble  

Microsoft Academic Search

Many problems, inherent in air traffic control, weather analysis and prediction, nuclear reaction, missile tracking, and hydrodynamics have common processing characteristics that can most efficiently be solved using parallel “non-conventional” techniques. Because of high sensor data rates, these parallel problem solving techniques cannot be economically applied using the standard sequential computer. The application of special processing techniques such as parallel\\/associative

Orin E. Marvel

1973-01-01

377

ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION  

E-print Network

ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION PATRICIA D. HOUGH, TAMARA G. KOLDA. 1, pp. 134­156 Abstract. We introduce a new asynchronous parallel pattern search (APPS). Parallel pattern search can be quite useful for engineering optimization problems characterized by a small number

Kolda, Tamara G.

378

ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION #  

E-print Network

ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION # PATRICIA D. HOUGH + , TAMARA G Mathematics Vol. 23, No. 1, pp. 134--156 Abstract. We introduce a new asynchronous parallel pattern search (APPS). Parallel pattern search can be quite useful for engineering optimization problems characterized

Kolda, Tamara G.

379

Parallel Processing at the High School Level.  

ERIC Educational Resources Information Center

This study investigated the ability of high school students to cognitively understand and implement parallel processing. Data indicates that most parallel processing is being taught at the university level. Instructional modules on C, Linux, and the parallel processing language, P4, were designed to show that high school students are highly…

Sheary, Kathryn Anne

380

Parallel VLSI Circuit Analysis and Optimization  

E-print Network

(Inter- and Intra- algorithm parallelism, using 8 threads) . . . . . . . . . . . . . . . . . 73 VI HMAPS implementation 1 (Inter-algorithm parallelism only, us- ing 4 threads) vs Newton+Gear2 . . . . . . . . . . . . . . . . . . . . 75 VII HMAPS... implementation 2 (Inter- and Intra-algorithm parallelism, using 8 threads) vs Newton+Gear2 . . . . . . . . . . . . . . . . . . . 75 VIII Computational component cost (in seconds) breakdown for each example circuit...

Ye, Xiaoji

2012-02-14

381

High Performance Parallel Computational Nanotechnology  

NASA Technical Reports Server (NTRS)

At a recent press conference, NASA Administrator Dan Goldin encouraged NASA Ames Research Center to take a lead role in promoting research and development of advanced, high-performance computer technology, including nanotechnology. Manufacturers of leading-edge microprocessors currently perform large-scale simulations in the design and verification of semiconductor devices and microprocessors. Recently, the need for this intensive simulation and modeling analysis has greatly increased, due in part to the ever-increasing complexity of these devices, as well as the lessons of experiences such as the Pentium fiasco. Simulation, modeling, testing, and validation will be even more important for designing molecular computers because of the complex specification of millions of atoms, thousands of assembly steps, as well as the simulation and modeling needed to ensure reliable, robust and efficient fabrication of the molecular devices. The software for this capacity does not exist today, but it can be extrapolated from the software currently used in molecular modeling for other applications: semi-empirical methods, ab initio methods, self-consistent field methods, Hartree-Fock methods, molecular mechanics; and simulation methods for diamondoid structures. In as much as it seems clear that the application of such methods in nanotechnology will require powerful, highly powerful systems, this talk will discuss techniques and issues for performing these types of computations on parallel systems. We will describe system design issues (memory, I/O, mass storage, operating system requirements, special user interface issues, interconnects, bandwidths, and programming languages) involved in parallel methods for scalable classical, semiclassical, quantum, molecular mechanics, and continuum models; molecular nanotechnology computer-aided designs (NanoCAD) techniques; visualization using virtual reality techniques of structural models and assembly sequences; software required to control mini robotic manipulators for positional control; scalable numerical algorithms for reliability, verifications and testability. There appears no fundamental obstacle to simulating molecular compilers and molecular computers on high performance parallel computers, just as the Boeing 777 was simulated on a computer before manufacturing it.

Saini, Subhash; Craw, James M. (Technical Monitor)

1995-01-01

382

GROMACS: A message-passing parallel molecular dynamics implementation  

NASA Astrophysics Data System (ADS)

A parallel message-passing implementation of a molecular dynamics (MD) program that is useful for bio(macro)molecules in aqueous environment is described. The software has been developed for a custom-designed 32-processor ring GROMACS (GROningen MAchine for Chemical Simulation) with communication to and from left and right neighbours, but can run on any parallel system onto which a a ring of processors can be mapped and which supports PVM-like block send and receive calls. The GROMACS software consists of a preprocessor, a parallel MD and energy minimization program that can use an arbitrary number of processors (including one), an optional monitor, and several analysis tools. The programs are written in ANSI C and available by ftp (information: gromacs@chem.rug.nl). The functionality is based on the GROMOS (GROningen MOlecular Simulation) package (van Gunsteren and Berendsen, 1987; BIOMOS B.V., Nijenborgh 4, 9747 AG Groningen). Conversion programs between GROMOS and GROMACS formats are included. The MD program can handle rectangular periodic boundary conditions with temperature and pressure scaling. The interactions that can be handled without modification are variable non-bonded pair interactions with Coulomb and Lennard-Jones or Buckingham potentials, using a twin-range cut-off based on charge groups, and fixed bonded interactions of either harmonic or constraint type for bonds and bond angles and either periodic or cosine power series interactions for dihedral angles. Special forces can be added to groups of particles (for non-equilibrium dynamics or for position restraining) or between particles (for distance restraints). The parallelism is based on particle decomposition. Interprocessor communication is largely limited to position and force distribution over the ring once per time step.

Berendsen, H. J. C.; van der Spoel, D.; van Drunen, R.

1995-09-01

383

Segmented ray casting for data parallel volume rendering  

Microsoft Academic Search

Interactive volume rendering is important for the timely analysis of three-dimensional data, but workstations take seconds to minutes to render data sets of a few megabytes. We have developed a parallel ray-casting technique. called Sepnenred Ray Cnsting, which can render a 128x128~128 data set at 2-3 frames per second on a 4K processor DECmpp 12OOO\\/Sx Model 100. Pixel values in

William M. Hsu

1993-01-01

384

Parallel Assembly of LIGA Components  

SciTech Connect

In this paper, a prototype robotic workcell for the parallel assembly of LIGA components is described. A Cartesian robot is used to press 386 and 485 micron diameter pins into a LIGA substrate and then place a 3-inch diameter wafer with LIGA gears onto the pins. Upward and downward looking microscopes are used to locate holes in the LIGA substrate, pins to be pressed in the holes, and gears to be placed on the pins. This vision system can locate parts within 3 microns, while the Cartesian manipulator can place the parts within 0.4 microns.

Christenson, T.R.; Feddema, J.T.

1999-03-04

385

Standard Templates Adaptive Parallel Library  

E-print Network

Radix Sort. 44 . . 47 . . . . 49 . . 31 REFEREiVCES . . 52 LIST OF FI('URES Figurc I STL Components Figure 2: STAPL. I igurc 3: A P Range and Its S Ranges Figurc 4: STAPI. Mechanism . . , 14 . 27 Fi urc 5: Class Hierarchy of P Ran c Figure... Figurc 12: Radix Sort (Spceduf'is) . . , 51 Vt LIST OF TABLES Tattle Page Non-tMutattng Funcuon Templates (Equivaicni to STI. ) Mutatmg Function Templates (Equivalent to STL) . . Numeric Function Templates (Equivalent to STL) 5 STAPL Parallel...

Arzu, Francisco Jose

2012-06-07

386

Fault-tolerant parallel processor  

SciTech Connect

This paper addresses issues central to the design and operation of an ultrareliable, Byzantine resilient parallel computer. Interprocessor connectivity requirements are met by treating connectivity as a resource that is shared among many processing elements, allowing flexibility in their configuration and reducing complexity. Redundant groups are synchronized solely by message transmissions and receptions, which aslo provide input data consistency and output voting. Reliability analysis results are presented that demonstrate the reduced failure probability of such a system. Performance analysis results are presented that quantify the temporal overhead involved in executing such fault-tolerance-specific operations. Empirical performance measurements of prototypes of the architecture are presented. 30 refs.

Harper, R.E.; Lala, J.H. (Charles Stark Draper Laboratory, Inc., Cambridge, MA (USA))

1991-06-01

387

Parallel multiscale simulations of a brain aneurysm  

PubMed Central

Cardiovascular pathologies, such as a brain aneurysm, are affected by the global blood circulation as well as by the local microrheology. Hence, developing computational models for such cases requires the coupling of disparate spatial and temporal scales often governed by diverse mathematical descriptions, e.g., by partial differential equations (continuum) and ordinary differential equations for discrete particles (atomistic). However, interfacing atomistic-based with continuum-based domain discretizations is a challenging problem that requires both mathematical and computational advances. We present here a hybrid methodology that enabled us to perform the first multi-scale simulations of platelet depositions on the wall of a brain aneurysm. The large scale flow features in the intracranial network are accurately resolved by using the high-order spectral element Navier-Stokes solver ?? ?r. The blood rheology inside the aneurysm is modeled using a coarse-grained stochastic molecular dynamics approach (the dissipative particle dynamics method) implemented in the parallel code LAMMPS. The continuum and atomistic domains overlap with interface conditions provided by effective forces computed adaptively to ensure continuity of states across the interface boundary. A two-way interaction is allowed with the time-evolving boundary of the (deposited) platelet clusters tracked by an immersed boundary method. The corresponding heterogeneous solvers ( ?? ?r and LAMMPS) are linked together by a computational multilevel message passing interface that facilitates modularity and high parallel efficiency. Results of multiscale simulations of clot formation inside the aneurysm in a patient-specific arterial tree are presented. We also discuss the computational challenges involved and present scalability results of our coupled solver on up to 300K computer processors. Validation of such coupled atomistic-continuum models is a main open issue that has to be addressed in future work. PMID:23734066

Grinberg, Leopold; Fedosov, Dmitry A.; Karniadakis, George Em

2012-01-01

388

Parallel program debugging with flowback analysis  

SciTech Connect

This thesis describes the design and implementation of an integrated debugging system for parallel programs running on shared memory multi-processors. The goal of the debugging system is to present to the programmer a graphical view of the dynamic program dependences while keeping the execution-time overhead low. The author first describes the use of flowback analysis to provide information on causal relationship between events in a programs' execution without re-executing the program for debugging. Execution time overhead is kept low by recording only a small amount of trace during a program's execution. He uses semantic analysis and a technique called incremental tracing to keep the time and space overhead low. As part of the semantic analysis, he uses a static program dependence graph structure that reduces the amount of work done at compile time and takes advantage of the dynamic information produced during execution time. The cornerstone of the incremental tracing concept is to generate a coarse trace during execution and fill incrementally, during the interactive portion of the debugging session, the gap between the information gathered in the coarse trace and the information needed to do the flowback analysis using the coarse trace. Then, he describes how to extend the flowback analysis to parallel programs. The flowback analysis can span process boundaries; i.e., the most recent modification to a shared variable might be traced to a different process than the one that contains the current reference. The static and dynamic program dependence graphs of the individual processes are tied together with synchronization and data dependence information to form complete graphs that represent the entire program.

Choi, Jongdeok.

1989-01-01

389

Automating parallel implementation of neural learning algorithms.  

PubMed

Neural learning algorithms generally involve a number of identical processing units, which are fully or partially connected, and involve an update function, such as a ramp, a sigmoid or a Gaussian function for instance. Some variations also exist, where units can be heterogeneous, or where an alternative update technique is employed, such as a pulse stream generator. Associated with connections are numerical values that must be adjusted using a learning rule, and and dictated by parameters that are learning rule specific, such as momentum, a learning rate, a temperature, amongst others. Usually, neural learning algorithms involve local updates, and a global interaction between units is often discouraged, except in instances where units are fully connected, or involve synchronous updates. In all of these instances, concurrency within a neural algorithm cannot be fully exploited without a suitable implementation strategy. A design scheme is described for translating a neural learning algorithm from inception to implementation on a parallel machine using PVM or MPI libraries, or onto programmable logic such as FPGAs. A designer must first describe the algorithm using a specialised Neural Language, from which a Petri net (PN) model is constructed automatically for verification, and building a performance model. The PN model can be used to study issues such as synchronisation points, resource sharing and concurrency within a learning rule. Specialised constructs are provided to enable a designer to express various aspects of a learning rule, such as the number and connectivity of neural nodes, the interconnection strategies, and information flows required by the learning algorithm. A scheduling and mapping strategy is then used to translate this PN model onto a multiprocessor template. We demonstrate our technique using a Kohonen and backpropagation learning rules, implemented on a loosely coupled workstation cluster, and a dedicated parallel machine, with PVM libraries. PMID:11011794

Rana, O F

2000-06-01

390

Parallel Rendering of Large Time-Varying Volume Data  

NASA Technical Reports Server (NTRS)

Interactive visualization of large time-varying 3D volume datasets has been and still is a great challenge to the modem computational world. It stretches the limits of the memory capacity, the disk space, the network bandwidth and the CPU speed of a conventional computer. In this SURF project, we propose to develop a parallel volume rendering program on SGI's Prism, a cluster computer equipped with state-of-the-art graphic hardware. The proposed program combines both parallel computing and hardware rendering in order to achieve an interactive rendering rate. We use 3D texture mapping and a hardware shader to implement 3D volume rendering on each workstation. We use SGI's VisServer to enable remote rendering using Prism's graphic hardware. And last, we will integrate this new program with ParVox, a parallel distributed visualization system developed at JPL. At the end of the project, we Will demonstrate remote interactive visualization using this new hardware volume renderer on JPL's Prism System using a time-varying dataset from selected JPL applications.

Garbutt, Alexander E.

2005-01-01

391

Implementation and performance of parallelized elegant.  

SciTech Connect

The program elegant is widely used for design and modeling of linacs for free-electron lasers and energy recovery linacs, as well as storage rings and other applications. As part of a multi-year effort, we have parallelized many aspects of the code, including single-particle dynamics, wakefields, and coherent synchrotron radiation. We report on the approach used for gradual parallelization, which proved very beneficial in getting parallel features into the hands of users quickly. We also report details of parallelization of collective effects. Finally, we discuss performance of the parallelized code in various applications.

Wang, Y.; Borland, M.; Accelerator Systems Division (APS)

2008-01-01

392

Xyce parallel electronic simulator design.  

SciTech Connect

This document is the Xyce Circuit Simulator developer guide. Xyce has been designed from the 'ground up' to be a SPICE-compatible, distributed memory parallel circuit simulator. While it is in many respects a research code, Xyce is intended to be a production simulator. As such, having software quality engineering (SQE) procedures in place to insure a high level of code quality and robustness are essential. Version control, issue tracking customer support, C++ style guildlines and the Xyce release process are all described. The Xyce Parallel Electronic Simulator has been under development at Sandia since 1999. Historically, Xyce has mostly been funded by ASC, the original focus of Xyce development has primarily been related to circuits for nuclear weapons. However, this has not been the only focus and it is expected that the project will diversify. Like many ASC projects, Xyce is a group development effort, which involves a number of researchers, engineers, scientists, mathmaticians and computer scientists. In addition to diversity of background, it is to be expected on long term projects for there to be a certain amount of staff turnover, as people move on to different projects. As a result, it is very important that the project maintain high software quality standards. The point of this document is to formally document a number of the software quality practices followed by the Xyce team in one place. Also, it is hoped that this document will be a good source of information for new developers.

Thornquist, Heidi K.; Rankin, Eric Lamont; Mei, Ting; Schiek, Richard Louis; Keiter, Eric Richard; Russo, Thomas V.

2010-09-01

393

Performance prediction for complex parallel applications  

SciTech Connect

Today`s massively parallel machines are typically message-passing systems consisting of hundreds or thousands of processors. Implementing parallel applications efficiently in this environment is a challenging task, and poor parallel design decisions can be expensive to correct. Tools and techniques that allow the fast and accurate evaluation of different parallelization strategies would significantly improve the productivity of application developers and increase throughput on parallel architectures. This paper investigates one of the major issues in building tools to compare parallelization strategies: determining what type of performance models of the application code and of the computer system are sufficient for a fast and accurate comparison of different strategies. The paper is built around a case study employing the Performance Prediction Tool (PerPreT) to predict performance of the Parallel Spectral Transform Shallow Water Model code (PSTSWM) on the Intel Paragon. 13 refs., 6 tabs.

Brehm, J. [Hannover Univ. (Germany). Inst. fuer Rechnerstrukturen und Betriebssysteme; Worley, P.H. [Oak Ridge National Lab., TN (United States)

1997-04-01

394

Hybrid Parallel Part I. Preliminaries  

E-print Network

Balancing Chapter 17. Interacting Tasks Chapter 18. MPI Part IV. GPU Accelerator Part V. Big Data #12. The task's command line argument strings are N, the number of most significant zero bits in the digest

Kaminsky, Alan

395

PERFORMANCE MEASUREMENT OF MONTE CARLO PHOTON TRANSPORT ON PARALLEL MACHINES  

E-print Network

particle transport is an inherently parallel (or embarrassingly parallel) computational method that has there is also interest to explore multithreaded architectures to improve parallel performance of scientific

Majumdar, Amit

396

Converting thread-level parallelism to instruction-level parallelism via simultaneous multithreading  

Microsoft Academic Search

To achieve high performance, contemporary computer systems rely on two forms of parallelism: instruction-level parallelism (ILP) and thread-level parallelism (TLP). Wide-issue super-scalar processors exploit ILP by executing multiple instructions from a single program in a single cycle. Multiprocessors (MP) exploit TLP by executing different threads in parallel on different processors. Unfortunately, both parallel processing styles statically partition processor resources, thus

Jack L. Lo; Joel S. Emer; Henry M. Levy; Rebecca L. Stamm; Dean M. Tullsen; S. J. Eggers

1997-01-01

397

Integrated Task and Data Parallel Programming  

NASA Technical Reports Server (NTRS)

This research investigates the combination of task and data parallel language constructs within a single programming language. There are an number of applications that exhibit properties which would be well served by such an integrated language. Examples include global climate models, aircraft design problems, and multidisciplinary design optimization problems. Our approach incorporates data parallel language constructs into an existing, object oriented, task parallel language. The language will support creation and manipulation of parallel classes and objects of both types (task parallel and data parallel). Ultimately, the language will allow data parallel and task parallel classes to be used either as building blocks or managers of parallel objects of either type, thus allowing the development of single and multi-paradigm parallel applications. 1995 Research Accomplishments In February I presented a paper at Frontiers 1995 describing the design of the data parallel language subset. During the spring I wrote and defended my dissertation proposal. Since that time I have developed a runtime model for the language subset. I have begun implementing the model and hand-coding simple examples which demonstrate the language subset. I have identified an astrophysical fluid flow application which will validate the data parallel language subset. 1996 Research Agenda Milestones for the coming year include implementing a significant portion of the data parallel language subset over the Legion system. Using simple hand-coded methods, I plan to demonstrate (1) concurrent task and data parallel objects and (2) task parallel objects managing both task and data parallel objects. My next steps will focus on constructing a compiler and implementing the fluid flow application with the language. Concurrently, I will conduct a search for a real-world application exhibiting both task and data parallelism within the same program. Additional 1995 Activities During the fall I collaborated with Andrew Grimshaw and Adam Ferrari to write a book chapter which will be included in Parallel Processing in C++ edited by Gregory Wilson. I also finished two courses, Compilers and Advanced Compilers, in 1995. These courses complete my class requirements at the University of Virginia. I have only my dissertation research and defense to complete.

Grimshaw, A. S.

1998-01-01

398

Parallel network simulations with NEURON.  

PubMed

The NEURON simulation environment has been extended to support parallel network simulations. Each processor integrates the equations for its subnet over an interval equal to the minimum (interprocessor) presynaptic spike generation to postsynaptic spike delivery connection delay. The performance of three published network models with very different spike patterns exhibits superlinear speedup on Beowulf clusters and demonstrates that spike communication overhead is often less than the benefit of an increased fraction of the entire problem fitting into high speed cache. On the EPFL IBM Blue Gene, almost linear speedup was obtained up to 100 processors. Increasing one model from 500 to 40,000 realistic cells exhibited almost linear speedup on 2,000 processors, with an integration time of 9.8 seconds and communication time of 1.3 seconds. The potential for speed-ups of several orders of magnitude makes practical the running of large network simulations that could otherwise not be explored. PMID:16732488

Migliore, M; Cannia, C; Lytton, W W; Markram, Henry; Hines, M L

2006-10-01

399

Parallel processing for scientific computations  

NASA Technical Reports Server (NTRS)

The main contribution of the effort in the last two years is the introduction of the MOPPS system. After doing extensive literature search, we introduced the system which is described next. MOPPS employs a new solution to the problem of managing programs which solve scientific and engineering applications on a distributed processing environment. Autonomous computers cooperate efficiently in solving large scientific problems with this solution. MOPPS has the advantage of not assuming the presence of any particular network topology or configuration, computer architecture, or operating system. It imposes little overhead on network and processor resources while efficiently managing programs concurrently. The core of MOPPS is an intelligent program manager that builds a knowledge base of the execution performance of the parallel programs it is managing under various conditions. The manager applies this knowledge to improve the performance of future runs. The program manager learns from experience.

Alkhatib, Hasan S.

1991-01-01

400

Parallel computing in enterprise modeling.  

SciTech Connect

This report presents the results of our efforts to apply high-performance computing to entity-based simulations with a multi-use plugin for parallel computing. We use the term 'Entity-based simulation' to describe a class of simulation which includes both discrete event simulation and agent based simulation. What simulations of this class share, and what differs from more traditional models, is that the result sought is emergent from a large number of contributing entities. Logistic, economic and social simulations are members of this class where things or people are organized or self-organize to produce a solution. Entity-based problems never have an a priori ergodic principle that will greatly simplify calculations. Because the results of entity-based simulations can only be realized at scale, scalable computing is de rigueur for large problems. Having said that, the absence of a spatial organizing principal makes the decomposition of the problem onto processors problematic. In addition, practitioners in this domain commonly use the Java programming language which presents its own problems in a high-performance setting. The plugin we have developed, called the Parallel Particle Data Model, overcomes both of these obstacles and is now being used by two Sandia frameworks: the Decision Analysis Center, and the Seldon social simulation facility. While the ability to engage U.S.-sized problems is now available to the Decision Analysis Center, this plugin is central to the success of Seldon. Because Seldon relies on computationally intensive cognitive sub-models, this work is necessary to achieve the scale necessary for realistic results. With the recent upheavals in the financial markets, and the inscrutability of terrorist activity, this simulation domain will likely need a capability with ever greater fidelity. High-performance computing will play an important part in enabling that greater fidelity.

Goldsby, Michael E.; Armstrong, Robert C.; Shneider, Max S.; Vanderveen, Keith; Ray, Jaideep; Heath, Zach; Allan, Benjamin A.

2008-08-01

401

Generalized formula for the surface stiffness of fluid-saturated porous media containing parallel pore channels  

E-print Network

Institute of Physics. Acoustic wave interaction with a plane interface separat- ing an ambient fluid to the average surface displacement of the fluid p p Ts Un un . 3 Generally, acoustic wave interaction with fluid/fluidGeneralized formula for the surface stiffness of fluid-saturated porous media containing parallel

Nagy, Peter B.

402

MASSIVELY PARALLEL MICROFLUIDIC CELL-PAIRING PLATFORM FOR THE STATISTICAL STUDY OF IMMUNOLOGICAL CELL-CELL  

E-print Network

MASSIVELY PARALLEL MICROFLUIDIC CELL-PAIRING PLATFORM FOR THE STATISTICAL STUDY OF IMMUNOLOGICAL CELL-CELL INTERACTIONS Melanie M. Hoehl1 , Stephanie K. Dougan2 , Hidde L. Ploegh2 , Joel Voldman3 1 of Electrical Engineering and Computer Science, MIT ABSTRACT Variability in cell-cell interactions is ubiquitous

Voldman, Joel

403

Instant well-log inversion with a parallel computer  

SciTech Connect

Well-log analysis requires several vectors of input data to be inverted with a physical model that produces more vectors of output data. The problem is inherently suited to either vectorization or parallelization. PLATO (parallel log analysis, timely output) is a research prototype system that uses a parallel architecture computer with memory-mapped graphics to invert vector data and display the result rapidly. By combining this high-performance computing and display system with a graphical user interface, the analyst can interact with the system in real time'' and can visualize the result of changing parameters on up to 1,000 levels of computed volumes and reconstructed logs. It is expected that such instant'' inversion will remove the main disadvantages frequently cited for simultaneous analysis methods, namely difficulty in assessing sensitivity to different parameters and slow output response. Although the prototype system uses highly specific features of a parallel processor, a subsequent version has been implemented on a conventional (Serial) workstation with less performance but adequate functionality to preserve the apparently instant response. PLATO demonstrates the feasibility of petroleum computing applications combining an intuitive graphical interface, high-performance computing of physical models, and real-time output graphics.

Kimminau, S.J.; Trivedi, H.

1993-08-01

404

Toward an automated parallel computing environment for geosciences  

NASA Astrophysics Data System (ADS)

Software for geodynamic modeling has not kept up with the fast growing computing hardware and network resources. In the past decade supercomputing power has become available to most researchers in the form of affordable Beowulf clusters and other parallel computer platforms. However, to take full advantage of such computing power requires developing parallel algorithms and associated software, a task that is often too daunting for geoscience modelers whose main expertise is in geosciences. We introduce here an automated parallel computing environment built on open-source algorithms and libraries. Users interact with this computing environment by specifying the partial differential equations, solvers, and model-specific properties using an English-like modeling language in the input files. The system then automatically generates the finite element codes that can be run on distributed or shared memory parallel machines. This system is dynamic and flexible, allowing users to address different problems in geosciences. It is capable of providing web-based services, enabling users to generate source codes online. This unique feature will facilitate high-performance computing to be integrated with distributed data grids in the emerging cyber-infrastructures for geosciences. In this paper we discuss the principles of this automated modeling environment and provide examples to demonstrate its versatility.

Zhang, Huai; Liu, Mian; Shi, Yaolin; Yuen, David A.; Yan, Zhenzhen; Liang, Guoping

2007-08-01

405

Parallel Computing for Terrestrial Ecosystem Carbon Modeling  

SciTech Connect

Terrestrial ecosystems are a primary component of research on global environmental change. Observational and modeling research on terrestrial ecosystems at the global scale, however, has lagged behind their counterparts for oceanic and atmospheric systems, largely because the unique challenges associated with the tremendous diversity and complexity of terrestrial ecosystems. There are 8 major types of terrestrial ecosystem: tropical rain forest, savannas, deserts, temperate grassland, deciduous forest, coniferous forest, tundra, and chaparral. The carbon cycle is an important mechanism in the coupling of terrestrial ecosystems with climate through biological fluxes of CO{sub 2}. The influence of terrestrial ecosystems on atmospheric CO{sub 2} can be modeled via several means at different timescales. Important processes include plant dynamics, change in land use, as well as ecosystem biogeography. Over the past several decades, many terrestrial ecosystem models (see the 'Model developments' section) have been developed to understand the interactions between terrestrial carbon storage and CO{sub 2} concentration in the atmosphere, as well as the consequences of these interactions. Early TECMs generally adapted simple box-flow exchange models, in which photosynthetic CO{sub 2} uptake and respiratory CO{sub 2} release are simulated in an empirical manner with a small number of vegetation and soil carbon pools. Demands on kinds and amount of information required from global TECMs have grown. Recently, along with the rapid development of parallel computing, spatially explicit TECMs with detailed process based representations of carbon dynamics become attractive, because those models can readily incorporate a variety of additional ecosystem processes (such as dispersal, establishment, growth, mortality etc.) and environmental factors (such as landscape position, pest populations, disturbances, resource manipulations, etc.), and provide information to frame policy options for climate change impact analysis.

Wang, Dali [ORNL; Post, Wilfred M [ORNL; Ricciuto, Daniel M [ORNL; Berry, Michael [University of Tennessee, Knoxville (UTK)

2011-01-01

406

Multipactor saturation in parallel-plate waveguides  

SciTech Connect

The saturation stage of a multipactor discharge is considered of interest, since it can guide towards a criterion to assess the multipactor onset. The electron cloud under multipactor regime within a parallel-plate waveguide is modeled by a thin continuous distribution of charge and the equations of motion are calculated taking into account the space charge effects. The saturation is identified by the interaction of the electron cloud with its image charge. The stability of the electron population growth is analyzed and two mechanisms of saturation to explain the steady-state multipactor for voltages near above the threshold onset are identified. The impact energy in the collision against the metal plates decreases during the electron population growth due to the attraction of the electron sheet on the image through the initial plate. When this growth remains stable till the impact energy reaches the first cross-over point, the electron surface density tends to a constant value. When the stability is broken before reaching the first cross-over point the surface charge density oscillates chaotically bounded within a certain range. In this case, an expression to calculate the maximum electron surface charge density is found whose predictions agree with the simulations when the voltage is not too high.

Sorolla, E.; Mattes, M. [Ecole Polytechnique Federale de Lausanne, Laboratoire d'Electromagnetisme et d'Acoustique (LEMA), Station 11, CH-1015 Lausanne (Switzerland)

2012-07-15

407

Generic implementations of parallel prefix sums and its applications  

E-print Network

synchronization as the number of processors increases. As part of the applications for parallel prefix sums, parallel radix sort and four parallel tree applications are built on top of the implementation. These applications are also fundamental parallel algorithms...

Huang, Tao

2009-05-15

408

Massachusetts Institute of Technology A Comparison of Implicitly Parallel Multithreaded  

E-print Network

CSAIL Massachusetts Institute of Technology A Comparison of Implicitly Parallel Multithreaded Multithreaded and Data Parallel Implementations of an Ocean Model Computation Structures Group Memo 364 Parallel Multithreaded and Data Parallel Implementations of an Ocean Model Andrew Shaw Arvind Kyoo

Gummadi, Ramakrishna

409

Multithreaded Parallelism and Performance Measures Marc Moreno Maza  

E-print Network

Multithreaded Parallelism and Performance Measures Marc Moreno Maza University of Western Ontario, London, Ontario (Canada) CS 3101 (Moreno Maza) Multithreaded Parallelism and Performance Measures CS 3101 and Implementation 4 Measuring Parallelism in Practice 5 Announcements (Moreno Maza) Multithreaded Parallelism

Moreno Maza, Marc

410

Parallelization Strategies for Mixed Regular-Irregular Applications on Multicore-Systems  

NASA Astrophysics Data System (ADS)

Scientific simulation codes often exhibit a mixed structure of regular and irregular data accesses. Since the organization of data accesses has a large influence on the overall performance of parallel code, a careful planning of parallelism is required. In this article, we consider a mixed regular-irregular particle simulation code and investigate several parallelization strategies for multicore architectures consisting of several multicore processors in a shared memory system. The interaction of irregular and regular data accesses are the specific challenge for a cache optimized parallel multicore-code. We present performance experiments on three different multicore systems and show that a mixture of parallelization techniques for irregular and regular applications leads to the best performance.

Rünger, Gudula; Schwind, Michael

411

Towards Distributed Memory Parallel Program Analysis  

SciTech Connect

This paper presents a parallel attribute evaluation for distributed memory parallel computer architectures where previously only shared memory parallel support for this technique has been developed. Attribute evaluation is a part of how attribute grammars are used for program analysis within modern compilers. Within this work, we have extended ROSE, a open compiler infrastructure, with a distributed memory parallel attribute evaluation mechanism to support user defined global program analysis required for some forms of security analysis which can not be addressed by a file by file view of large scale applications. As a result, user defined security analyses may now run in parallel without the user having to specify the way data is communicated between processors. The automation of communication enables an extensible open-source parallel program analysis infrastructure.

Quinlan, D; Barany, G; Panas, T

2008-06-17

412

Parallel automated adaptive procedures for unstructured meshes  

NASA Technical Reports Server (NTRS)

Consideration is given to the techniques required to support adaptive analysis of automatically generated unstructured meshes on distributed memory MIMD parallel computers. The key areas of new development are focused on the support of effective parallel computations when the structure of the numerical discretization, the mesh, is evolving, and in fact constructed, during the computation. All the procedures presented operate in parallel on already distributed mesh information. Starting from a mesh definition in terms of a topological hierarchy, techniques to support the distribution, redistribution and communication among the mesh entities over the processors is given, and algorithms to dynamically balance processor workload based on the migration of mesh entities are given. A procedure to automatically generate meshes in parallel, starting from CAD geometric models, is given. Parallel procedures to enrich the mesh through local mesh modifications are also given. Finally, the combination of these techniques to produce a parallel automated finite element analysis procedure for rotorcraft aerodynamics calculations is discussed and demonstrated.

Shephard, M. S.; Flaherty, J. E.; Decougny, H. L.; Ozturan, C.; Bottasso, C. L.; Beall, M. W.

1995-01-01

413

Linearly exact parallel closures for slab geometry  

SciTech Connect

Parallel closures are obtained by solving a linearized kinetic equation with a model collision operator using the Fourier transform method. The closures expressed in wave number space are exact for time-dependent linear problems to within the limits of the model collision operator. In the adiabatic, collisionless limit, an inverse Fourier transform is performed to obtain integral (nonlocal) parallel closures in real space; parallel heat flow and viscosity closures for density, temperature, and flow velocity equations replace Braginskii's parallel closure relations, and parallel flow velocity and heat flow closures for density and temperature equations replace Spitzer's parallel transport relations. It is verified that the closures reproduce the exact linear response function of Hammett and Perkins [Phys. Rev. Lett. 64, 3019 (1990)] for Landau damping given a temperature gradient. In contrast to their approximate closures where the vanishing viscosity coefficient numerically gives an exact response, our closures relate the heat flow and nonvanishing viscosity to temperature and flow velocity (gradients)

Ji, Jeong-Young; Held, Eric D. [Department of Physics, Utah State University, Logan, Utah 84322 (United States)] [Department of Physics, Utah State University, Logan, Utah 84322 (United States); Jhang, Hogun [National Fusion Research Institute, 52 Yeoeun-dong, Yusung-Gu, Daejon (Korea, Republic of)] [National Fusion Research Institute, 52 Yeoeun-dong, Yusung-Gu, Daejon (Korea, Republic of)

2013-08-15

414

Applications on emerging paradigms in parallel computing  

Microsoft Academic Search

The area of computing is seeing parallelism increasingly being incorporated at various levels: from the lowest levels of vector processing units following Single Instruction Multiple Data (SIMD) processing, Simultaneous Multi-threading (SMT) architectures, and multi\\/many-cores with thread-level shared memory and SIMT parallelism, to the higher levels of distributed memory parallelism as in supercomputers and clusters, and scaling them to large distributed

Abhinav Sarje

2010-01-01

415

Theoretical dynamic response of electrostatic parallel plate  

NASA Astrophysics Data System (ADS)

Theoretical dynamic response of an electrostatic parallel plate to a time varying voltage has been obtained as a function of the applied voltage. The nonlinear equation of motion is theoretically solved for the dynamic response when ac drive voltage with dc bias voltage actuates the movable plate of the parallel plate with small amplitude. The dynamic response is expressed in a closed form to perform research on a variety of microactuators and sensors employing parallel plates.

Lee, Ki Bang

2007-10-01

416

Prototyping parallel and distributed programs in Proteus  

Microsoft Academic Search

This paper presents Proteus, an architecture-independent language suitable for prototyping parallel and distributed programs. Proteus is a high-level imperative notation based on sets and sequences with a single construct for the parallel composition of processes. Although a shared-memory model is the basis for communication between processes, this memory can be partitioned into shared and private variables. Parallel processes operate on

Peter H. Millst; Lars S. Nyland; Jan F. Prim; John H. Reift; Robert A. Wagnert

1991-01-01

417

Automatic Multilevel Parallelization Using OpenMP  

NASA Technical Reports Server (NTRS)

In this paper we describe the extension of the CAPO parallelization support tool to support multilevel parallelism based on OpenMP directives. CAPO generates OpenMP directives with extensions supported by the NanosCompiler to allow for directive nesting and definition of thread groups. We report first results for several benchmark codes and one full application that have been parallelized using our system.

Jin, Hao-Qiang; Jost, Gabriele; Yan, Jerry; Ayguade, Eduard; Gonzalez, Marc; Martorell, Xavier; Biegel, Bryan (Technical Monitor)

2002-01-01

418

Analysis of the numerical effects of parallelism on a parallel genetic algorithm  

SciTech Connect

This paper examines the effects of relaxed synchronization on both the numerical and parallel efficiency of parallel genetic algorithms (GAs). We describe a coarse-grain geographically structured parallel genetic algorithm. Our experiments show that asynchronous versions of these algorithms have a lower run time than-synchronous GAs. Furthermore, we demonstrate that this improvement in performance is partly due to the fact that the numerical efficiency of the asynchronous genetic algorithm is better than the synchronous genetic algorithm. Our analysis includes a critique of the utility of traditional parallel performance measures for parallel GAs, and we evaluate the claims made by several researchers that parallel GAs can have superlinear speedup.

Hart, W.E.; Belew, R.K.; Kohn, S. [Sandia National Labs., Albuquerque, NM (United States); Baden, S. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Computer Science and Engineering

1995-09-18

419

Conformal pure radiation with parallel rays  

NASA Astrophysics Data System (ADS)

We define pure radiation metrics with parallel rays to be n-dimensional pseudo-Riemannian metrics that admit a parallel null line bundle K and whose Ricci tensor vanishes on vectors that are orthogonal to K. We give necessary conditions in terms of the Weyl, Cotton and Bach tensors for a pseudo-Riemannian metric to be conformal to a pure radiation metric with parallel rays. Then, we derive conditions in terms of the tractor calculus that are equivalent to the existence of a pure radiation metric with parallel rays in a conformal class. We also give analogous results for n-dimensional pseudo-Riemannian pp-waves.

Leistner, Thomas; Nurowski, Pawe?

2012-03-01

420

Parallel Genetic Algorithm for Alpha Spectra Fitting  

NASA Astrophysics Data System (ADS)

We present a performance study of alpha-particle spectra fitting using parallel Genetic Algorithm (GA). The method uses a two-step approach. In the first step we run parallel GA to find an initial solution for the second step, in which we use Levenberg-Marquardt (LM) method for a precise final fit. GA is a high resources-demanding method, so we use a Beowulf cluster for parallel simulation. The relationship between simulation time (and parallel efficiency) and processors number is studied using several alpha spectra, with the aim of obtaining a method to estimate the optimal processors number that must be used in a simulation.

García-Orellana, Carlos J.; Rubio-Montero, Pilar; González-Velasco, Horacio

2005-01-01

421

A parallel algorithm for global routing  

NASA Technical Reports Server (NTRS)

A Parallel Hierarchical algorithm for Global Routing (PHIGURE) is presented. The router is based on the work of Burstein and Pelavin, but has many extensions for general global routing and parallel execution. Main features of the algorithm include structured hierarchical decomposition into separate independent tasks which are suitable for parallel execution and adaptive simplex solution for adding feedthroughs and adjusting channel heights for row-based layout. Alternative decomposition methods and the various levels of parallelism available in the algorithm are examined closely. The algorithm is described and results are presented for a shared-memory multiprocessor implementation.

Brouwer, Randall J.; Banerjee, Prithviraj

1990-01-01

422

Parallel Computation for Natural Convection in Cavities  

NASA Technical Reports Server (NTRS)

Parallel computation for thermal convective flows in cavities with adiabatic horizontal boundaries and driven by differential heating of the two vertical end walls, is investigated using supercomputers. A parallel computation code has been implemented using a finite-difference method with a multigrid elliptic solver and a Dufort-Frankel scheme. The domain decomposition techniques are discussed in detail. The parallel code is numerically stable, computationally efficient, and portable to various parallel architectures which support either PVM or NX libraries for communications. Finally, numerical results for various Rayleigh numbers and Prandtl numbers are presented.

Wang, P.; Ferraro, R. D.

1995-01-01

423

Parallel auto-correlative statistics with VTK.  

SciTech Connect

This report summarizes existing statistical engines in VTK and presents both the serial and parallel auto-correlative statistics engines. It is a sequel to [PT08, BPRT09b, PT09, BPT09, PT10] which studied the parallel descriptive, correlative, multi-correlative, principal component analysis, contingency, k-means, and order statistics engines. The ease of use of the new parallel auto-correlative statistics engine is illustrated by the means of C++ code snippets and algorithm verification is provided. This report justifies the design of the statistics engines with parallel scalability in mind, and provides scalability and speed-up analysis results for the autocorrelative statistics engine.

Pebay, Philippe Pierre [Kitware, France; Bennett, Janine Camille

2013-08-01

424

A Parallel Multigrid Method for Neutronics Applications  

SciTech Connect

The multigrid method has been shown to be the most effective general method for solving the multi-dimensional diffusion equation encountered in neutronics. This being the method of choice, we develop a strategy for implementing the multigrid method on computers of massively parallel architecture. This leads us to strategies for parallelizing the relaxation, contraction (interpolation), and prolongation operators involved in the method. We then compare the efficiency of our parallel multigrid with other parallel methods for solving the diffusion equation on selected problems encountered in reactor physics.

Alcouffe, Raymond E.

2001-01-01

425

Parallel programming in Split-C  

SciTech Connect

The authors introduce the Split-C language, a parallel extension of C intended for high performance programming on distributed memory multiprocessors, and demonstrate the use of the language in optimizing parallel programs. Split-C provides a global address space with a clear concept of locality and unusual assignment operators. These are used as tools to reduce the frequency and cost of remote access. The language allows a mixture of shared memory, message passing, and data parallel programming styles while providing efficient access to the underlying machine. They demonstrate the basic language concepts using regular and irregular parallel programs and give performance results for various stages of program optimization.

Culler, D.E.; Dusseau, A.; Goldstein, S.C.; Krishnamurthy, A.; Lumetta, S.; Eicken, T. von; Yelick, K. [Univ. of California, Berkeley, CA (United States). Computer Science Division

1993-12-31

426

Parallel Computational Steering for HPC Applications Using HDF5 Files in Distributed Shared Memory  

Microsoft Academic Search

Interfacing a GUI driven visualization\\/analysis package to an HPC application enables a supercomputer to be used as an interactive instrument. We achieve this by replacing the IO layer in the HDF5 library with a custom driver which transfers data in parallel between simulation and analysis. Our implementation using ParaView as the interface, allows a flexible combination of parallel simulation, concurrent

John Biddiscombe; Jerome Soumagne; Guillaume Oger; David Guibert; Jean-Guillaume Piccinali

2012-01-01

427

Automated Parallel Recordings of Topologically Identified Single Ion Channels  

PubMed Central

Although ion channels are attractive targets for drug discovery, the systematic screening of ion channel-targeted drugs remains challenging. To facilitate automated single ion-channel recordings for the analysis of drug interactions with the intra- and extracellular domain, we have developed a parallel recording methodology using artificial cell membranes. The use of stable lipid bilayer formation in droplet chamber arrays facilitated automated, parallel, single-channel recording from reconstituted native and mutated ion channels. Using this system, several types of ion channels, including mutated forms, were characterised by determining the protein orientation. In addition, we provide evidence that both intra- and extracellular amyloid-beta fragments directly inhibit the channel open probability of the hBK channel. This automated methodology provides a high-throughput drug screening system for the targeting of ion channels and a data-intensive analysis technique for studying ion channel gating mechanisms. PMID:23771282

Kawano, Ryuji; Tsuji, Yutaro; Sato, Koji; Osaki, Toshihisa; Kamiya, Koki; Hirano, Minako; Ide, Toru; Miki, Norihisa; Takeuchi, Shoji

2013-01-01

428

Loosely coupled parallel network simulator  

SciTech Connect

This patent describes a network simulator for simulating a plurality of parallel processing networks. It comprises: a buses for transmitting information segments to processing sites; each of the busses includes data line means to transmit an information segment, at least one control line means to transmit control information related to the information segment; and a reply line means for indicating that another processing site is coupled to the bus to receive the information segment; sets of processing sites each set being coupled to a given one of the plurality of buses, each processing site having a processor means and interface means coupling the processor to the bus; clock means coupled to each of the interface means to synchronize time intervals during which the respective interface means couples it corresponding processor means to its corresponding bus; time multiplex switching means coupled to each of the buses to receive an information segment from one of the busses for transmission on another of the buses; and each of the interface means including sequencing means coupled to the clock means to select during which time interval the corresponding processor means is to be coupled to its respective bus.

Woodward, T.R.

1990-07-17

429

Virtual reality visualization of parallel molecular dynamics simulation  

SciTech Connect

When performing communications mapping experiments for massively parallel processors, it is important to be able to visualize the mappings and resulting communications. In a molecular dynamics model, visualization of the atom to atom interaction and the processor mappings provides insight into the effectiveness of the communications algorithms. The basic quantities available for visualization in a model of this type are the number of molecules per unit volume, the mass, and velocity of each molecule. The computational information available for visualization is the atom to atom interaction within each time step, the atom to processor mapping, and the energy resealing events. We use the CAVE (CAVE Automatic Virtual Environment) to provide interactive, immersive visualization experiences.

Disz, T.; Papka, M.; Stevens, R.; Pellegrino, M. [Argonne National Lab., IL (United States); Taylor, V. [Northwestern Univ., Evanston, IL (United States). Electrical Engineering and Computer Science

1995-12-31

430

Conservation of writhe helicity under anti-parallel reconnection  

E-print Network

Reconnection is a fundamental event in many areas of science, from the interaction of vortices in classical and quantum fluids, and magnetic flux tubes in magnetohydrodynamics and plasma physics, to the recombination in polymer physics and DNA biology. By using fundamental results in topological fluid mechanics, the helicity of a flux tube can be calculated in terms of writhe and twist contributions. Here we show that the writhe is conserved under anti-parallel reconnection. Hence, for a pair of interacting flux tubes of equal flux, if the twist of the reconnected tube is the sum of the original twists of the interacting tubes, then helicity is conserved during reconnection. Thus, any deviation from helicity conservation is entirely due to the intrinsic twist inserted or deleted locally at the reconnection site. This result has important implications for helicity and energy considerations in various physical contexts.

Laing, Christian E; Sumners, De Witt L

2014-01-01

431

Conservation of writhe helicity under anti-parallel reconnection  

E-print Network

Reconnection is a fundamental event in many areas of science, from the interaction of vortices in classical and quantum fluids, and magnetic flux tubes in magnetohydrodynamics and plasma physics, to the recombination in polymer physics and DNA biology. By using fundamental results in topological fluid mechanics, the helicity of a flux tube can be calculated in terms of writhe and twist contributions. Here we show that the writhe is conserved under anti-parallel reconnection. Hence, for a pair of interacting flux tubes of equal flux, if the twist of the reconnected tube is the sum of the original twists of the interacting tubes, then helicity is conserved during reconnection. Thus, any deviation from helicity conservation is entirely due to the intrinsic twist inserted or deleted locally at the reconnection site. This result has important implications for helicity and energy considerations in various physical contexts.

Christian E. Laing; Renzo L. Ricca; De Witt L. Sumners

2014-10-14

432

The language parallel Pascal and other aspects of the massively parallel processor  

NASA Technical Reports Server (NTRS)

A high level language for the Massively Parallel Processor (MPP) was designed. This language, called Parallel Pascal, is described in detail. A description of the language design, a description of the intermediate language, Parallel P-Code, and details for the MPP implementation are included. Formal descriptions of Parallel Pascal and Parallel P-Code are given. A compiler was developed which converts programs in Parallel Pascal into the intermediate Parallel P-Code language. The code generator to complete the compiler for the MPP is being developed independently. A Parallel Pascal to Pascal translator was also developed. The architecture design for a VLSI version of the MPP was completed with a description of fault tolerant interconnection networks. The memory arrangement aspects of the MPP are discussed and a survey of other high level languages is given.

Reeves, A. P.; Bruner, J. D.

1982-01-01

433

Are expectations for parallelism too high? A survey for potential parallel users  

SciTech Connect

Parallel computing has been portrayed as a technology that enables users to solve very large and complex problems very quickly. But has this portrayal created unreasonably high expectations for potential parallel users? This paper reports the results of a survey designed to delineate the differences in how computer scientists and technical programmers approach parallel programming. Responses from 326 ``potential parallel programmers`` at Supercomputing `93 are presented. The analysis provides information about the costs and benefits associated with parallel programming, application development activities, and the extent of tool use in those activities. It shows that users expect very dramatic gains in performance from parallel machines, while underestimating the amount of effort that will be needed. The results should be of interest to parallel tool developers and people involved in training parallel programmers.

Cook, C.R.; Pancake, C.M.; Walpole, R. [Oregon State Univ., Corvallis, OR (United States). Dept. of Computer Science

1994-12-31

434

Blade-mounted trailing edge flap control for BVI noise reduction  

NASA Technical Reports Server (NTRS)

Numerical procedures based on the 2-D and 3-D full potential equations and the 2-D Navier-Stokes equations were developed to study the effects of leading and trailing edge flap motions on the aerodynamics of parallel airfoil-vortex interactions and on the aerodynamics and acoustics of the more general self-generated rotor blade vortex interactions (BVI). For subcritical interactions, the 2-D results indicate that the trailing edge flap can be used to alleviate the impulsive loads experienced by the airfoil. For supercritical interactions, the results show the necessity of using a leading edge flap, rather than a trailing edge flap, to alleviate the interaction. Results for various time dependent flap motions and their effect on the predicted temporal sectional loads, differential pressures, and the free vortex trajectories are presented. For the OLS model rotor, contours of a BVI noise metric were used to quantify the effects of the trailing edge flap on the size and directivity of the high/low intensity noise region(s). Average reductions in the BVI noise levels on the order of 5 dB with moderate power penalties on the order of 18 pct. for a four bladed rotor and 58 pct. for a two bladed rotor were obtained.

Hassan, A. A.; Charles, B. D.; Tadghighi, H.; Sankar, L. N.

1992-01-01

435

Sequential and parallel algorithms for minimum cost parallel decomposition of finite state machines  

E-print Network

SEQUENTIAL AND PARALLEL ALGORITHMS FOR MINIMUM COST PARALLEL DECOMPOSITION OF FINITE STATE MACHINES A Thesis by RAJENDRA RAM SHELKE Submitted to the Office of Graduate Studies of Texas ASM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1992 Major Subject: Electrical Engineering SEQUENTIAL AND PARALLEL ALGORITHMS FOR IvIINIMUM COST PARALLEL DECOMPOSITION OF FINITE STATE MACHINES A Thesis by RAJENDRA RAM SHELKE Approved as to style and content by...

Shelke, Rajendra Ram

2012-06-07

436

Parallel processing in power systems computation  

Microsoft Academic Search

The availability of parallel processing hardware and software presents an opportunity and a challenge to apply this new computation technology to solve power system problems. The allure of parallel processing is that this technology has the potential to be cost effectively used on computationally intense problems. The objective of this paper is to define the state of the art and

D. J. Tylavsky; A. Bose; F. Alvarado; R. Betancourt; K. Clements; G. T. Heydt; G. Huang; M. Ilic; M. La Scala; M. A. Pai

1992-01-01

437

An exercise in proving parallel programs correct  

Microsoft Academic Search

A parallel program, Dijkstra's on-the-fly garbage collector, is proved correct using a proof method developed by Owicki. The fine degree of interleaving in this program makes it especially difficult to understand, and complicates the proof greatly. Difficulties with proving such parallel programs correct are discussed.

David Gries

1975-01-01

438

Exploring Parallelization Strategies for NUFFT Data Translation  

E-print Network

Exploring Parallelization Strategies for NUFFT Data Translation Yuanrui Zhang Mahmut Kandemir parallelization strategies for the Non-Uniform FFT (NUFFT) data translation on multicore architectures. The NUFFT and image processing as well as in scientific computing. The critical extension lies at the translation

Pitsianis, Nikos P.

439

Parallel Evolution and Inheritance of Quantitative Traits  

Microsoft Academic Search

Parallel phenotypic evolution, the independent evolution of the same trait in closely related lineages, is interesting because it tells us about the contribution of natural selection to phenotypic evolution. Haldane and others have proposed that parallel evolution also results from a second process, the similarly biased production of genetic variation in close relatives, an idea that has received few tests.

Dolph Schluter; Maria Nemethy

2004-01-01

440

Parallel Education and Defining the Fourth Sector.  

ERIC Educational Resources Information Center

Parallel to the primary, secondary, postsecondary, and adult/community education sectors is education not associated with formal programs--learning in arts and cultural sites. The emergence of cultural and educational tourism is an opportunity for adult/community education to define itself by extending lifelong learning opportunities into parallel…

Chessell, Diana

1996-01-01

441

Parallel processing of numerical transport algorithms  

SciTech Connect

The multigroup, discrete ordinates representation for the linear transport equation enjoys widespread computational use and popularity. Serial solution schemes and numerical algorithms developed over the years provide a timely framework for parallel extension. On the Denelcor HEP, we investigate the parallel structure and extension of a number of standard S/sub n/ approaches. Concurrent inner sweeps, coupled acceleration techniques, synchronized inner-outer loops, and chaotic iteration are described, and results of computations are contrasted. The multigroup representation and serial iteration methods are also detailed. The basic iterative S/sub n/ method lends itself to parallel tasking, portably affording an effective medium for performing transport calculations on future architectures. This analysis represents a first attempt to extend serial S/sub n/ algorithms to parallel environments and provides good baseline estimates on ease of parallel implementation, relative algorithm efficiency, comparative speedup, and some future directions. We find basic inner-outer and chaotic iteration strategies both easily support comparably high degrees of parallelism. Both accommodate parallel rebalance and diffusion acceleration and appear as robust and viable parallel techniques for S/sub n/ production work.

Wienke, B.R.; Hiromoto, R.E.

1984-01-01

442

Parallel Algorithms for Data Mining Peter Christen  

E-print Network

Architectures: Two Examples CSIRO Capricorn ANU DCS Bunyip -- Sun Enterprise 4500 Server -- Beowulf Linux) the ANU Beowulf is Australia's fastest supercomputer. 3 17 May 2000 #12; Parallel Algorithms for Data Mining Peter Christen Parallel Architectures: ANU Beowulf Topology A B C D 48­Port Switch 24 x 100MB

Christen, Peter

443

A parallel indexed algorithm for information retrieval  

Microsoft Academic Search

In this paper we present a parallel document ranking algorithm suitable for use on databases of 1-1000 GB, resident on primary or secondary storage. The algorithm is based on inverted indexes, and has two advantages over a previously published parallel algorithm for retrieval based on signature files. First, it permits the employment of ranking strategies which cannot be easily implemented

Craig Stanfill; Robert Thau; David L. Waltz

1989-01-01

444

Non-Cartesian parallel imaging reconstruction.  

PubMed

Non-Cartesian parallel imaging has played an important role in reducing data acquisition time in MRI. The use of non-Cartesian trajectories can enable more efficient coverage of k-space, which can be leveraged to reduce scan times. These trajectories can be undersampled to achieve even faster scan times, but the resulting images may contain aliasing artifacts. Just as Cartesian parallel imaging can be used to reconstruct images from undersampled Cartesian data, non-Cartesian parallel imaging methods can mitigate aliasing artifacts by using additional spatial encoding information in the form of the nonhomogeneous sensitivities of multi-coil phased arrays. This review will begin with an overview of non-Cartesian k-space trajectories and their sampling properties, followed by an in-depth discussion of several selected non-Cartesian parallel imaging algorithms. Three representative non-Cartesian parallel imaging methods will be described, including Conjugate Gradient SENSE (CG SENSE), non-Cartesian generalized autocalibrating partially parallel acquisition (GRAPPA), and Iterative Self-Consistent Parallel Imaging Reconstruction (SPIRiT). After a discussion of these three techniques, several potential promising clinical applications of non-Cartesian parallel imaging will be covered. J. Magn. Reson. Imaging 2014;40:1022-1040. © 2014 Wiley Periodicals, Inc. PMID:24408499

Wright, Katherine L; Hamilton, Jesse I; Griswold, Mark A; Gulani, Vikas; Seiberlich, Nicole

2014-11-01

445

Designing a Parallel Object Oriented Graphics Framework  

E-print Network

Designing a Parallel Object Oriented Graphics Framework Robert F. Tobler Vienna University of Technology, Austria Abstract. This paper aims to present a design strategy for graphics frameworks issues of parallelization, that can be seamlessly integrated into graphics frameworks which have been

446

Theoretical dynamic response of electrostatic parallel plate  

Microsoft Academic Search

Theoretical dynamic response of an electrostatic parallel plate to a time varying voltage has been obtained as a function of the applied voltage. The nonlinear equation of motion is theoretically solved for the dynamic response when ac drive voltage with dc bias voltage actuates the movable plate of the parallel plate with small amplitude. The dynamic response is expressed in

Ki Bang Lee

2007-01-01

447

Parallel simulation of the Sharks World problem  

Microsoft Academic Search

The Sharks World problem has been suggested as a suitable application to evaluate the effectiveness of parallel simulation algorithms. This paper develops a simulation model in Maisie, a C-based simulation language. With minor modifications, a Maisie progrmm may be executed using either sequential or parallel simulation algorithms. The paper presents the results of executing the Maisie model on a multicomputer

Rajive L. Bagrodia; Wen-Toh Liao

1990-01-01

448

A Parallel Architecture perspective on language processing  

Microsoft Academic Search

This article sketches the Parallel Architecture, an approach to the structure of grammar that contrasts with mainstream generative grammar (MGG) in that (a) it treats phonology, syntax, and semantics as independent generative components whose structures are linked by interface rules; (b) it uses a parallel constraint-based formalism that is nondirectional; (c) it treats words and rules alike as pieces of

Ray Jackendoff

2007-01-01

449

Parallel Programming with Matrix Distributed Processing  

E-print Network

Matrix Distributed Processing (MDP) is a C++ library for fast development of efficient parallel algorithms. It constitues the core of FermiQCD. MDP enables programmers to focus on algorithms, while parallelization is dealt with automatically and transparently. Here we present a brief overview of MDP and examples of applications in Computer Science (Cellular Automata), Engineering (PDE Solver) and Physics (Ising Model).

Massimo Di Pierro

2005-05-09

450

Parallel programming with message passing and directives  

Microsoft Academic Search

The authors discuss methods for expressing and tuning the performance of parallel programs, using two programming models in the same program: distributed and shared memory. Such methods are important for anyone who uses these large machines for parallel programs as well as for those who study combinations of the two programming models. The article outlines applications in hydrology, computational chemistry,

S. W. Bova; C. P. Breshears; HENRY GABB; BOB KUHN; BILL MAGRO; RUDOLF EIGENMANN; GREG GAERTNER; STEFANO SALVINI; HOWARD SCOTT

2001-01-01

451

Computing Flow Transition On Parallel Processors  

NASA Technical Reports Server (NTRS)

Parallel algorithm developed on multiple-microprocessor computer. Program initiated to develop computer codes capable of directly simulating and mathematically modeling transition process at mach numbers ranging from subsonic to hypersonic. Parallel computers potentially offer reduction of processing time; processing time inversely proportional to number of available processors.

Bokhari, S.; Erlebacher, G.; Hussaini, M. Y.

1993-01-01

452

Parallel Global Aircraft Configuration Design Space Exploration  

E-print Network

Parallel Global Aircraft Configuration Design Space Exploration CHUCK A. BAKER, LAYNE T. WATSON of a parallel computer. Section 2 describes the aircraft design problem, Section 3 gives the direct search, BERNARD GROSSMAN, WILLIAM H. MASON Multidisciplinary Analysis and Design (MAD) Center for Advanced

Neumaier, Arnold

453

RAM-Based parallel-output controller  

NASA Technical Reports Server (NTRS)

Selected bit strings in serial-data link are extracted for processing. Controller is programmable interface between serial-data link and peripherals that accept parallel data. It can be used to drive displays, printers, plotters, digital-to-analog converters, and parallel-output ports.

Niswander, J. K.; Stattel, R. J.

1980-01-01

454

Abstract AndParallel Machines Nachum Dershowitz  

E-print Network

Abstract And­Parallel Machines Nachum Dershowitz University of Illinois Urbana, IL 61801 U are introduced. The first of them, the And­ Parallel Turing Machine, can be viewed as a generalization of the deterministic Turing machine in which the infinite tape is replaced by an infinite tree­like tape on which

Dershowitz, Nachum

455

Batch Scheduling with Deadlines on Parallel Machines  

E-print Network

Batch Scheduling with Deadlines on Parallel Machines Peter Brucker Mikhail Y. Kovalyov, Yakov M of scheduling G groups of jobs on m parallel machines is considered. Each group consists of several identical) and to schedule the batches on the machines. It is possible for different batches of the same group

Magdeburg, Universität

456

Parallel Activation in Bilingual Phonological Processing  

ERIC Educational Resources Information Center

In bilingual language processing, the parallel activation hypothesis suggests that bilinguals activate their two languages simultaneously during language processing. Support for the parallel activation mainly comes from studies of lexical (word-form) processing, with relatively less attention to phonological (sound) processing. According to…

Lee, Su-Yeon

2011-01-01

457

Parallel Computing for Seismic Geotechnical Applications  

Microsoft Academic Search

Parallel computing is gradually becoming a main stream tool in geotechnical simulations. The need for high fidelity and for modeling of fairly large 3 -dimensional (3D) spatial configurations is motivating this direct ion of research. A new program ParC YCLIC for seismic geotechnical applications has been developed. Salient characteristics of the employed parallel sparse solver will be presented. Using this

Jinchi Lu; Ahmed Elgamal; Kincho H. Law; Zhaohui Yang

458

Parallelizing Support Vector Machines on Distributed Computers  

Microsoft Academic Search

Support Vector Machines (SVMs) suffer from a widely recognized scalability problem in both memory use and computational time. To improve scalability, we have developed a parallel SVM algorithm (PSVM), which reduces memory use through performing a row-based, approximate matrix factorization, and which loads only essential data to each machine to perform parallel computation. Let n denote the number of training

Edward Y. Chang; Kaihua Zhu; Hao Wang; Hongjie Bai; Jian Li; Zhihuan Qiu; Hang Cui

2007-01-01

459

Logic verification algorithms and their parallel implementation  

Microsoft Academic Search

LOVER incorporates a novel approach to combinational logic verification and obtains good results when compared to existing techniques. In this paper we describe a new verification algorithm, LOVER-PODEM, whose enumeration phase is based on PODEM. A variant of LOVER-PODEM, called PLOVER, is presented. We have developed, for the first time, parallel logic verification schemes. Issues in efficiently parallelizing both general

Hi-Keung Tony Ma; Srinivas Devadas; Alberto L. Sangiovanni-Vincentelli; R. Wei

1987-01-01

460

The Web as a Parallel Corpus  

Microsoft Academic Search

Parallel corpora have become an essential resource for work in multilingual natural language processing. In this article, we report on our work using the STRAND system for mining parallel text on the World Wide Web,first reviewing the original algorithm and results and then presenting a set of significant enhancements. These enhancements include the use of supervised learning based on structural

Philip Resnik; Noah A. Smith

2003-01-01

461

Parallel Imports: Challenges from Unauthorized Distribution Channels  

Microsoft Academic Search

We examine the problem of parallel imports: unauthorized flows of products across countries, which compete with authorized distribution channels. The traditional economics model of a discriminating monopolist that has different prices for the same good in different markets requires the markets to be separated in some way, usually geographically. The profits from price discrimination can be threatened by parallel imports

Reza Ahmadi; B. Rachel Yang

2000-01-01

462

Data-Parallel String-Manipulating Programs  

Microsoft Academic Search

Applications ranging from malware detection to graphics to Web security sanitization depend on string transformations, but writing such transformations is a challenge. Making these transformations run in parallel on a cluster of machines or special hardware is an even greater challenge. We answer this challenge with fast, parallel string manipulating code compiled from BEK, a domain-specific language for writing complex

Margus Veanes; David Molnar; Todd Mytkowicz; Benjamin Livshits

2012-01-01

463

Parallel programming in Split-C  

Microsoft Academic Search

The authors introduce the Split-C language, a parallel extension of C intended for high performance programming on distributed memory multiprocessors, and demonstrate the use of the language in optimizing parallel programs. Split-C provides a global address space with a clear concept of locality and unusual assignment operators. These are used as tools to reduce the frequency and cost of remote

A. Krishnamurthy; D. E. Culler; A. Dusseau; S. C. Goldstein; Steven Lumetta; Thorsten von Eicken; Katherine A. Yelick

1993-01-01

464

The Feature Space in Parallel Grammar Writing  

Microsoft Academic Search

This paper discusses the methodology and tools applied in the Parallel Gram- mar project (ParGram) to support con- sistency and parallelism of linguistic representations across multilingual Lex- ical Functional Grammar (LFG) gram- mars. A particular issue is that the gram- mars in the ParGram project are de- veloped at different international sites. The approach that was established over several years

Miriam Butt; Tracy Holloway King; Jonas Kuhn

2004-01-01

465

The Cilk System for Parallel Multithreaded Computing  

Microsoft Academic Search

Although cost-effective parallel machines are now commercially available, the widespreaduse of parallel processing is still being held back, due mainly to the troublesome nature ofparallel programming. In particular, it is still difficult to build efficient implementations ofparallel applications whose communication patterns are either highly irregular or dependentupon dynamic information. Multithreading has become an increasingly popular way toimplement these dynamic, asynchronous,...

Christopher F. Joerg

1996-01-01

466

A Parallel Approach to Syntax for Generation  

Microsoft Academic Search

To produce good utterances from non-trivial inputs a natural language generator should consider many words in parallel, which raises the question of how to handle syntax in a parallel generator. If a generator is incremental and centered on the task of word choice, then the role of syntax is merely to help evaluate the appropriateness of words. One way to

Nigel Ward

1992-01-01

467

IBM Parallel Environment for Linux Introduction  

E-print Network

IBM Parallel Environment for Linux Introduction Version 4 Release 2 SA23-2218-00 #12;#12;IBM Parallel Environment for Linux Introduction Version 4 Release 2 SA23-2218-00 #12;Note Before using for Linux (product number 5724-N05) and to all subsequent releases and modifications until otherwise

Hickman, Mark

468

Parallel Support Set Searches for Meshfree Methods  

Microsoft Academic Search

Abstract. We describe the implementation of a parallel algorithm which solves a computational geometry problem arising in meshfree methods. We solve the following problem: Given a collection of N d-rectangles Si and P points xk in R,-trees (for example, octrees for the case d = 3). Parallel issues of load balancing and characteristics of the collections of sets and points

C. Cartwright; Suely Oliveira; David E. Stewart

2006-01-01

469

Dynamic load balancing of parallel cellular automata  

Microsoft Academic Search

We are interested in running in parallel cellular automata. We present an algorithm which explores the dynamic remapping of cells in order to balance the load between the processing nodes. The parallel application runs on a cluster of PCs con- nected by Fast-Ethernet. A general cellular automaton can be described as a set of cells where each cell is a

Marc Mazzariol; Benoit A. Gennart; Roger D. Hersch Ecole

2000-01-01

470

Dynamic load balancing of parallel cellular automata  

Microsoft Academic Search

We are interested in running in parallel cellular automata. We present an algorithm which explores the dynamic remapping of cells in order to balance the load between processing nodes. The parallel application runs on a cluster of PCs connected by Fast-Ethernet. A general cellular automaton can be described as a set of cells where each cell is a state machine.

Marc Mazzariol; Benoit A. Gennart; Roger David Hersch

2000-01-01

471

Parallelizing the Closure Computation in Automated Deduction  

Microsoft Academic Search

In this paper we present a parallel algorithm for computing the closure of a set under an operation. This particular type of computation appears in a variety of disguises, and has been used in automated theorem proving, abstract algebra, and formal logic. The algorithm we give here is particularly suited for shared-memory parallel computers, where it makes possible economies of

John K. Slaney; Ewing L. Lusk

1990-01-01

472

Parallel Genetic Programming for Decision Tree Induction  

Microsoft Academic Search

A parallel genetic programming approach to induce decision trees in large data sets is presented. A population of trees is evolved by employing the genetic operators and every individual is evaluated by using a fitness function based on the J-measure. The method is able to deal with large data sets since it uses a parallel implementation of genetic programming through

Gianluigi Folino; Clara Pizzuti; Giandomenico Spezzano

2001-01-01

473

Task Parallelism and Data Distribution: An Overview of Explicit Parallel Programming Languages  

E-print Network

Task Parallelism and Data Distribution: An Overview of Explicit Parallel Programming Languages-level languages use explicit constructs for communication patterns and specifying the number and placement.lastname@mines-paristech.fr Abstract. Programming parallel machines as effectively as sequential ones would ideally require a language

Paris-Sud XI, Université de

474

Hardware for Speculative Parallelization of Partially-Parallel Loops in DSM Multiprocessors 1  

E-print Network

Hardware for Speculative Parallelization of Partially-Parallel Loops in DSM Multiprocessors 1 Ye in parallel in an e#11;ective manner on Distributed Shared-Memory (DSM) mul- tiprocessors, some important proceeds, extra hardware added to the directory-based cache coherence of the DSM machine detects

Torrellas, Josep

475

Analysis of the Numerical Effects of Parallelism on a Parallel Genetic Algorithm \\Lambda William E. Hart  

E-print Network

have a lower run time than syn­ chronous GAs. Our analysis shows that this improvement is due to (1 observed to ``prematurely converge'' to nonoptimal solutions. Many parallel GAs are designed in such a way of parallel genetic algorithms (GAs). We describe a coarse­grain geo­ graphically structured parallel genetic

Baden, Scott B.

476

A parallel gravitational N-body kernel  

E-print Network

We describe source code level parallelization for the {\\tt kira} direct gravitational $N$-body integrator, the workhorse of the {\\tt starlab} production environment for simulating dense stellar systems. The parallelization strategy, called ``j-parallelization'', involves the partition of the computational domain by distributing all particles in the system among the available processors. Partial forces on the particles to be advanced are calculated in parallel by their parent processors, and are then summed in a final global operation. Once total forces are obtained, the computing elements proceed to the computation of their particle trajectories. We report the results of timing measurements on four different parallel computers, and compare them with theoretical predictions. The computers employ either a high-speed interconnect, a NUMA architecture to minimize the communication overhead or are distributed in a grid. The code scales well in the domain tested, which ranges from 1024 - 65536 stars on 1 - 128 proc...

Zwart, Simon Portegies; Groen, Derek; Gualandris, Alessia; Sipior, Michael; Vermin, Willem

2007-01-01

477

Parallel tempering for the traveling salesman problem  

SciTech Connect

We explore the potential of parallel tempering as a combinatorial optimization method, applying it to the traveling salesman problem. We compare simulation results of parallel tempering with a benchmark implementation of simulated annealing, and study how different choices of parameters affect the relative performance of the two methods. We find that a straightforward implementation of parallel tempering can outperform simulated annealing in several crucial respects. When parameters are chosen appropriately, both methods yield close approximation to the actual minimum distance for an instance with 200 nodes. However, parallel tempering yields more consistently accurate results when a series of independent simulations are performed. Our results suggest that parallel tempering might offer a simple but powerful alternative to simulated annealing for combinatorial optimization problems.

Percus, Allon [Los Alamos National Laboratory; Wang, Richard [UCLA MATH DEPT; Hyman, Jeffrey [UCLA MATH DEPT; Caflisch, Russel [UCLA MATH DEPT

2008-01-01

478

Case studies in asynchronous data parallelism  

SciTech Connect

Is the owner-computes style of parallelism, captured in a variety of data parallel languages, attractive as a paradigm for designing explicit control parallel codes? This question gives rise to a number of others. Will such use be unwieldy? Will the resulting code run well? What can such an approach offer beyond merely replicating, in a more labor intensive way, the services and coverage of data parallel languages? We investigate these questions via a simple example and {open_quotes}real world{close_quotes} case studies developed using C-Linda, a language for explicit parallel programming formed by the merger of C with the Linda coordination language. The results demonstrate owner-computes is an effective design strategy in Linda.

Carriero, N.; Gelernter, D. [Yale Univ., New Haven, CT (United States)

1994-04-01

479

A parallel variable metric optimization algorithm  

NASA Technical Reports Server (NTRS)

An algorithm, designed to exploit the parallel computing or vector streaming (pipeline) capabilities of computers is presented. When p is the degree of parallelism, then one cycle of the parallel variable metric algorithm is defined as follows: first, the function and its gradient are computed in parallel at p different values of the independent variable; then the metric is modified by p rank-one corrections; and finally, a single univariant minimization is carried out in the Newton-like direction. Several properties of this algorithm are established. The convergence of the iterates to the solution is proved for a quadratic functional on a real separable Hilbert space. For a finite-dimensional space the convergence is in one cycle when p equals the dimension of the space. Results of numerical experiments indicate that the new algorithm will exploit parallel or pipeline computing capabilities to effect faster convergence than serial techniques.

Straeter, T. A.

1973-01-01

480

Parallel hypergraph partitioning for scientific computing.  

SciTech Connect

Graph partitioning is often used for load balancing in parallel computing, but it is known that hypergraph partitioning has several advantages. First, hypergraphs more accurately model communication volume, and second, they are more expressive and can better represent nonsymmetric problems. Hypergraph partitioning is particularly suited to parallel sparse matrix-vector multiplication, a common kernel in scientific computing. We present a parallel software package for hypergraph (and sparse matrix) partitioning developed at Sandia National Labs. The algorithm is a variation on multilevel partitioning. Our parallel implementation is novel in that it uses a two-dimensional data distribution among processors. We present empirical results that show our parallel implementation achieves good speedup on several large problems (up to 33 million nonzeros) with up to 64 processors on a Linux cluster.

Heaphy, Robert; Devine, Karen Dragon; Catalyurek, Umit (Ohio State University, Columbus); Bisseling, Robert (Utrecht University, The Netherlands); Hendrickson, Bruce Alan; Boman, Erik Gunnar

2005-07-01