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run-time parallelization of large FEM analyses with PERMAS

ADVANCES IN ENGINEERING SOFTWARE 1998年第3-6期29卷 241-248页

作者： Ast, M Fischer, R Labarta, J Manz, H INTES Ingenieurgesellsch Tech Software MBH Stuttgart Germany Univ Politecn Catalunya Barcelona Spain

The general purpose finite element (EE) system PERMAS(1) has been extended to support shared and distributed parallel computer architectures as well as workstation clusters. The methods used to parallelize this large application software package are of high generality and have the capability to parallelize all mathematical operations in a FE analysis-not only the solver. Utilizing the existing hyper-matrix data structure for large, sparsely populated matrices, a programming tool called PTM was introduced that automatically parallelizes block matrix operations on-the-fly. PTM totally hides parallelization from higher order algorithms, thus giving the physically oriented expert a virtually sequential programming environment. An operation graph of sub-matrix operations is asynchronously built and executed. A clustering algorithm distributes the work, performing a dynamic load balancing and exploiting data locality. Furthermore, a distributed data management system allows free data access from each node. The generality of the approach is demonstrated by some benchmark examples dealing with different types of FE analyses. (C) 1998 Elsevier Science Ltd. All rights reserved.

关键词： finite element analysis PERMAS run-time parallelization dynamic task graph hyper-matrix

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EXPLORER: Supporting run-time parallelization of DOACROSS loops on general networks of workstations

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PARALLEL COMPUTING 2000年第2-3期26卷 355-375页

作者： Liu, YL King, CT Natl Tsing Hua Univ Dept Comp Sci Hsinchu 30043 Taiwan

Performing run-time parallelization on general networks of workstations (NOWs) without special hardware or system software supports is very difficult, especially for DOACROSS loops. Parallelizing DOACROSS loops at run time implies complex operations for dependence detection, data accesses, and computation scheduling, which is hard to do systematically and could induce a large amount of messages. With the high communication overhead on NOWs, there is hardly any performance gain for run-time parallelization of DOACROSS loops. This paper proposes a general methodology for run-time parallelization of DOACROSS loops on NOWs, The methodology is realized by a portable run-time environment called EXPLORER, which can be implemented entirely at the user level. EXPLORER hides the communication overhead as much as possible through multithreading - a facility supported in almost all workstations. Considerations involved in the design of EXPLORER and its general organization will be introduced. Preliminary performance of EXPLORER will be presented and discussed. Performance measured on an implementation of EXPLORER on eight DEC Alpha workstations connected through a 10-Mbps Ethernet shows that the computation to communication ratio plays an important role and the extent to which multithreading can hide the communication overhead is limited. Thus EXPLORER is more suitable for coarse-grain computations. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： DOACROSS loops multithreading networks of workstations run-time parallelization

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Worker-checker - A framework for run-time parallelization on multiprocessors

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JOURNAL OF SYSTEMS ARCHITECTURE 1998年第3期45卷 205-229页

作者： Liu, KC King, CT Natl Tsing Hua Univ Dept Comp Sci Hsinchu 300 Taiwan

run-time parallelization is a technique for solving problems whose data access patterns are difficult to analyze at compile time. In this paper we propose a worker-checker framework to classify different run-time parallelization schemes. Under the framework, operations performed during run-time parallelization are classified loosely into a worker and a checker. Different schemes are then cast into the framework based on the relative execution order of their worker and checker. From the framework, we identified several new run-time parallelization methods. In the second part of the paper we then examine the implementation of one such method derived from speculative parallelization [L. Rauchwerger, D. Padua, Proceedings of 1995 Conference on Programming Language Design and Implementation, 1995]. The implementation is based on the idea of embedding hardware checkers inside memory controllers. We will present the design of the hardware checker and evaluate the effectiveness of the design on run-time parallelizing DOALL and DOACROSS loops. (C) 1998 Elsevier Science B.V. All rights reserved.

关键词： run-time parallelization speculative parallelization inspector-executor irregular problem smart memory

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run-time support for the automatic parallelization of Java programs

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JOURNAL OF SUPERCOMPUTING 2004年第1期28卷 91-117页

作者： Chan, B Abdelrahman, TS Univ Toronto Dept Elect & Comp Engn Edward S Rogers Sr Dept Elect & Comp Engn Toronto ON M5S 3G4 Canada

We describe and evaluate a novel approach for the automatic parallelization of programs that use pointer-based dynamic data structures, written in Java. The approach exploits parallelism among methods by creating an asynchronous thread of execution for each method invocation in a program. At compile time, methods are analyzed to determine the data they access, parameterized by their context. A description of these data accesses is transmitted to a run-time system during program execution. The run-time system utilizes this description to determine when a thread may execute, and to enforce dependences among threads. This run-time system is the main focus of this paper. More specifically, the paper details the representation of data accesses in a method and the framework used by the run-time system to detect and enforce dependences among threads. Experimental evaluation of an implementation of the run-time system on a four-processor Sun multiprocessor indicates that close to ideal speedup can be obtained for a number of benchmarks. This validates our approach.

关键词： automatic parallelization parallelizing compilers Java optimizations run-time parallelization task-level parallelism

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Evaluating automatic parallelization in SUIF

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2000年第1期11卷 36-49页

作者： Moon, S So, B Hall, MW Univ So Calif Inst Informat Sci Marina Del Rey CA 90292 USA

This paper presents the results of an experiment to measure empirically the remaining opportunities for exploiting loop-level parallelism that are missed by the Stanford SUIF compiler, a state-of-the-art automatic parallelization system targeting shared-memory multiprocessor architectures. For the purposes of this experiment, we have developed a run-time parallelization test called the Extended Lazy Privatizing Dealt (ELPD) test, which is able to simultaneously test multiple loops in a loop nest. The ELPD test identifies a specific type of parallelism where each iteration of the loop being tested accesses independent data. possibly by making some of the data private to each processor. For 29 programs in three benchmark suites, the ELPD test was executed at run time for each candidate loop left unparallelized by the SUIF compiler to identify which of these loops could safely execute in parallel for the given program input. The results of this experiment point to two main requirements for improving the effectiveness of parallelizing compiler technology: incorporating control flow tests into analysis and extracting low-cost run-time parallelization tests from analysis results.

关键词： parallelizing compilers shared-memory multiprocessors data dependence analysis array privatization run-time parallelization

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run -time optimization of adaptive irregular applications

Run -time optimization of adaptive irregular applications

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作者： Yu, Hao Texas A&M University

学位级别：Ph.D.

Compared to traditional compile-time optimization, run-time optimization could offer significant performance improvements when parallelizing and optimizing adaptive irregular applications, because it performs program analysis and adaptive optimizations during program execution. run-time techniques can succeed where static techniques fail because they exploit the characteristics of input data, programs' dynamic behaviors, and the underneath execution environment. When optimizing adaptive irregular applications for parallel execution, a common observation is that the effectiveness of the optimizing transformations depends on programs' input data and their dynamic phases. This dissertation presents a set of run-time optimization techniques that match the characteristics of programs' dynamic memory access patterns and the appropriate optimization (parallelization) transformations. First, we present a general adaptive algorithm selection framework to automatically and adaptively select at run-time the best performing, functionally equivalent algorithm for each of its execution instances. The selection process is based on off-line automatically generated prediction models and characteristics (collected and analyzed dynamically) of the algorithm's input data, In this dissertation, we specialize this framework for automatic selection of reduction algorithms. In this research, we have identified a small set of machine independent high-level characterization parameters and then we deployed an off-line, systematic experiment process to generate prediction models. These models, in turn, match the parameters to the best optimization transformations for a given machine. The technique has been evaluated thoroughly in terms of applications, platforms, and programs' dynamic behaviors. Specifically, for the reduction algorithm selection, the selected performance is within 2% of optimal performance and on average is 60% better than “Replicated Buffer,” the default parallel reduction a

关键词： compiler optimizations adaptive optimization performance modeling run-time parallelization run-time optimization reduction parallelization Book Thesis

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Efficient run-time scheduling for parallelizing partially parallel loops

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JOURNAL OF INFORMATION SCIENCE AND ENGINEERING 1998年第1期14卷 255-264页

作者： Huang, TC Hsu, PH Sheng, TN Natl Sun Yat Sen Univ Dept Elect Engn Kaohsiung Taiwan

For loops with irregular, non-linear, or run-time determined accesses to array elements, many scientific and engineering programs rely on aggressive run-time techniques to exploit the potential parallelism of these loops. In this paper, we propose an efficient run-time technique to find an optimal parallel execution schedule for partially parallel loops in which synchronization between certain iterations is required to ensure correct program semantics. For efficiency, the inspector phase and scheduler phase are combined into a single parallel scheduler. The scheduler partitions loop iterations into several chunks and then schedules the iterations in one chunk into wavefronts concurrently at run-time. Our scheme not only runs much efficiently, but also obtains an optimal schedule. We make use of an atomic bitwise-OR instruction to avoid global synchronization overhead and ensure that the larger wavefront value is preserved when the wavefront variable of an iteration is simultaneously updated during scheduling.

关键词： run-time parallelization partially parallel loop shared-memory multiprocessors inspector-executor wavefront

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