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international symposium on parallel and Distributed Processing (IPDPS)

作者： Cheolwhan Lee Tao Yang Yuan-Fang Wang Department of Computer Science University of California Santa Barbara CA USA

ISBN: (纸本)0818671955

Many computer vision and image processing (CVIP) operations can be represented as a sequence of tasks with nested loops, specified by the visual programming language Khoros. This paper addresses the automatic partitioning and scheduling of such operations on distributed memory multiprocessors. The major difficulties in determining the optimal image data distribution for each task are that the number of processors available and the size of the input image may vary at the run time, and the cost of some image processing operations may be data-dependent. This paper proposes a compile-time processor assignment and data partitioning scheme that optimizes the average run-time performance of task chains with nested loops by considering the data redistribution overheads and possible run-time parameter variations. This paper presents the theoretical analysis and experimental results on a Meiko CS-2 distributed memory machine.

关键词： Image processing Processor scheduling Runtime Partitioning algorithms Dynamic scheduling Computer science Cost function Computer vision Concurrent computing Distributed computing

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A communication+computation load balanced loop partitioning method

A communication+computation load balanced loop partitioning ...

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international symposium on parallel and Distributed Processing (IPDPS)

作者： S. Pande School of Electrical Engineering and Computer Science Ohio University Athens OH USA

We present an iteration and data partitioning approach for DOALL loops on distributed memory systems. The method first examines the highest amount of parallelism (available parallelism) which could be potentially exploited in a loop nest. It then examines the amount of communication overhead which can potentially nullify the benefits due to parallelism and attempts to maximally eliminate the communication to minimize the loop completion time by trading parallelism to a minimal extent. This is achieved by determining the directions of iteration space partitioning which result in minimum communication. Finally, in order to generate a load balanced partition with respect to computation+communication, the method uses a new larger partition owns rule to distribute the underlying data. Necessary theoretical framework has been developed and the merit of the method is shown through a performance evaluation on Cray T3D.

关键词： parallel processing Computer science Distributed computing programming Data communication Distribution functions Costs Partitioning algorithms

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An evaluation of DELTA, a decoupled pre-fetching virtual shared memory system

An evaluation of DELTA, a decoupled pre-fetching virtual sha...

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international symposium on parallel and Distributed Processing (IPDPS)

作者： I. Watson A. Rawsthorne M. Cumpstey F. Charpin Department Computer Science University of Manchester Institute of Science and Technology Manchester UK

Decoupled pre-fetching is a technique for reducing the page miss overheads in Distributed Shared Memory systems by separating out those instructions responsible for data fetching from the main instruction stream and running them on a separate CPU whose function is to predict store accesses ahead of time. This approach differs from other pre-fetching approaches in that the predictions of data usage are obtained dynamically from partial evaluation of the program and this promises to produce considerably better performance in circumstances where the access patterns are non-regular and cannot be extracted by static analysis of the program. This paper reviews the techniques of decoupled pre-fetching with particular emphasis on Cache only Memory architectures (COMA). It then presents a more thorough evaluation of the ideas than has previously been attempted using some of the SPLASH benchmarks. It is shown that the techniques perform well on some programs but that, as expected, the benefits of pre-fetching are negated when there is a high rate of data invalidation caused by global updating.

关键词： Memory architecture Yarn Switches Computer science Data mining Distributed decision making Delay programming profession Program processors Data structures

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Supporting I/O-efficient scientific computation in TPIE

Supporting I/O-efficient scientific computation in TPIE

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international symposium on parallel and Distributed Processing (IPDPS)

作者： D.E. Vengroff J. Scott Vitter Department of Computer Science Brown University Providence RI USA Department of Computer Science Duke University Durham NC USA

We describe the facilities that TPIE provides to support scientific computation. TPIE, a transparent parallel I/O environment, is a system designed to assist programmers in implementing I/O-efficient computations. It supports I/O-efficient paradigms for problems from a variety of domains, including sorting and permuting, computational geometry, graph algorithms, and scientific computation. Our main focus in on the algorithmic issues faced in designing the portions of TPIE that support scientific computation. We consider four computing paradigms: scanning, sorting, sparse matrix methods, and dense matrix methods. Benchmark results using TPIE are also briefly described. References to more detailed discussions of these benchmarks, as well as the overall goals, philosophy, and structure of TPIE are provided.

关键词： Computer science Concurrent computing Algorithm design and analysis Sorting Sparse matrices Large-scale systems Bandwidth Disk drives Prototypes programming profession

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Simulations of interacting many body systems using p4

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international JOURNAL OF HIGH SPEED COMPUTING 1995年第3期7卷 327-349页

作者： Scalettar, RT Runge, KJ Correa, J Lee, P Oklobdzija, V Vujic, JL UNIV CALIF DAVIS DEPT ELECT & COMP ENGNDAVISCA 95616 UNIV CALIF BERKELEY DEPT NUCL ENGNBERKELEYCA 94720

Monte Carlo (MC) and Molecular Dynamics (MD) simulations are powerful tools for understanding the low temperature properties of systems of interacting electrons and phonons in a solid, including the phenomena of magnetism and superconductivity. When mobile electrons are studied, these simulations are currently limited to a few hundred particles, and also largely to ''clean'' systems where no defects are present. Therefore, more powerful machines and algorithms must be used to address many of the most important issues in the field. In this paper, we present results from using some simple implementations of the p4 parallel programming system on a variety of parallel architectures to conduct MC and MD simulations of one and two dimensional electron-phonon models.

关键词： parallel Monte Carlo methods message passing p4

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Time-constrained code compaction for DSPs

Time-constrained code compaction for DSPs

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international symposium on System Synthesis

作者： R. Leupers P. Marwedel Department of Computer Science XII University of Dortmund Dortmund Germany

DSP algorithms are, in most cases, subject to hard real-time constraints. In the case of programmable DSPs, meeting those constraints must be ensured by appropriate code generation techniques. For processors offering instruction-level parallelism, the task of code generation includes code compaction. The exact timing behavior of a DSP program is only known after compaction. Therefore, real-time constraints should be taken into account during the compaction phase. While most known DSP code generators rely on rigid heuristics for that phase, this paper proposes a novel approach to local code compaction based on an integer programming model, which obeys exact timing constraints. Due to a general problem formulation, the model also obeys encoding restrictions and possible side-effects.

关键词： Compaction Digital signal processing Timing Time factors Constraint optimization Instruction sets Registers Hardware Computer science parallel processing

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parallel COMPUTATIONAL CHEMISTRY MADE EASIER - THE DEVELOPMENT OF NWCHEM

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international JOURNAL OF QUANTUM CHEMISTRY 1995年第S29期56卷 475-483页

作者： BERNHOLDT, DE APRA, E FRUCHTL, HA GUEST, MF HARRISON, RJ KENDALL, RA KUTTEH, RA LONG, X NICHOLAS, JB NICHOLS, JA TAYLOR, HL WONG, AT PACIFIC NW LAB ENVIRONM MOLEC SCI LAB HIGH PERFORMANCE COMP SOFTWARE SUPPORT RICHLAND WA 99352 USA

We describe the design philosophy, structure, and supporting tool kits of the NWChem computational chemistry package. The primary purpose of this effort was to develop efficient parallel algorithms for a broad range of methods commonly used in computational chemistry. To facilitate this, we developed a shared nonuniform access memory model which simplifies parallel programming while at the same time providing for portability across both distributed- and shared-memory machines. In addition to this specific focus on parallelization, a substantial effort has been made to simplify the general problem of large-scale software development, which is common to many research groups. We find that this simplification can be achieved through judicious use of ideas from the computer science field of software engineering in the design and implementation of the program with minimal extra effort on the part of the chemist. (C) John Wiley & Sons, Inc.

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Efficient communication using total-exchange

Efficient communication using total-exchange

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international symposium on parallel Processing

作者： Satish Rao T. Suel T. Tsantilas M. Goudreau NCE Research Institute Princeton NJ USA Department of Computer Science Columbia University New York NY USA Department of Computer Science University of Central Florida Orlando FL USA

A central question in parallel computing is to determine the extent to which one can write parallel programs using a high-level, general-purpose, and architecture-independent programming language and have them executed on a variety of parallel and distributed architectures without sacrificing efficiency. A large body of research suggests that, at least in theory, general-purpose parallel computing is indeed possible provided certain conditions are met: an excess of logical parallelism in the program, and the ability of the target architecture to efficiently realize balanced communication patterns. The canonical example of a balanced communication pattern is an h-relation, in which each processor is the origin and destination of at most h messages. A plethora of protocols has been designed for routing h-relations in a variety of networks. The goal has been to minimize the value of h while guaranteeing delivery of the messages within a time constant factor from optimal. In this paper we describe protocols that meet the most stringent efficiency requirement, namely delivery of messages within time that is a lower order additive term from the best achievable. Such protocols are called 1-optimal. While these protocols achieve 1-optimality only for heavily loaded networks, that is, for large values of h, they are remarkable for their simplicity in that they only use the total-exchange communication primitive. The total-exchange can be realized in many networks using very simple, contention-free, and extremely efficient schemes. The technical contribution of this paper is a protocol to route random h-relations in an N-processor network using /sup h///sub N/(1+o(1))+O(log log N) total-exchange rounds with high probability. Using message duplication, we can improve the bound to /sup h///sub N/(1+o(1))+O(log*N). This improves upon the /sup h///sub N/(1+o(1))+O(log N) bound of Gerbessiotis and Valiant. While our theoretical improvements are modest, our experimental results sho

关键词： parallel processing Concurrent computing National electric code Computer science Routing protocols Optical computing Computer languages Computer architecture Phase change random access memory Context

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Preemptive scheduling of duoprocessor tasks on dedicated processors to minimize schedule length

Preemptive scheduling of duoprocessor tasks on dedicated pro...

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international Conference on Emerging Technologies and Factory Automation (ETFA)

作者： M. Kubale Foundations of Informatics Department Technical University of Gdansk GdaDsk Poland

In this paper we have analyzed the algorithmic complexity of preemptive scheduling of duoprocessor tasks on dedicated processors in the case where the number of machines is arbitrary. We have proved this problem to be NP-hard even if all tasks have the same processing time. In other words, this means that it is practically impossible to give an efficient polynomially bounded algorithm for finding optimal schedules. However, if the number of machines is fixed, we can solve our problem in polynomial time. Again, this means that we can use a practically efficient algorithm simplex to solve this problem to optimality. The general NP-hardness of a scheduling problem does not exclude the existence of efficient algorithms for some special cases allowing arbitrarily many machines. Therefore, in the second part of this paper we have identified a number of such special cases involving a simplified structure of scheduling graphs. Finally, we have pointed out some important equivalence between finding a minimum makespan schedule and establishing a fractional chromatic coloring of the edges of associated graph.

关键词： Processor scheduling parallel algorithms Informatics Concurrent computing Fault tolerant systems System testing Computer networks Application software Tree graphs Linear programming

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The predictability of branches in libraries

The predictability of branches in libraries

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IEEE/ACM international symposium on Microarchitecture (MICRO)

作者： B. Calder D. Grunwald A. Srivastava Department of Computer Science University of Colorado Boulder CO USA Western Research Laboratory Digital Equipment Corporation Palo Alto CA USA

Profile-based optimizations are being used with increasing frequency. Profile information can be used to improve instruction scheduling, code layout, and to increase instruction level parallelism. These optimizations have been shown to be effective when they are applied to the same program from which the profile was gathered. However it is an open question how profile-based optimizations should be applied to library subroutines. If many programs use libraries in the same way, it may be possible to "preoptimize" a library or to use an optimized shared library. This study examines the use of commonly used libraries among 43 C and FORTRAN programs to see if the libraries have common behavior across different programs. We examine the behavior of the most commonly used Unix libraries on Digital Unix. We found that libraries have very predictable behavior between applications. This implies that profile-based compiler optimizations may be effective far libraries across different applications. Therefore, one can use profile optimizations on shared and non-shared libraries before they are shipped, allowing a program using those libraries to take advantage of profile-based optimizations without having to gather any profiles. All results in this study are shown using branch misprediction rates. We feel this metric indicates the likelihood that programs have similar behavior and allows comparison to earlier branch prediction studies.

关键词： Software libraries Optimizing compilers Application software Computer science Frequency Processor scheduling parallel processing algorithms programming profession Accuracy

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