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dynamic parallelization Strategies for Multifrontal Sparse Cholesky Factorization 13th

13th International Conference on Parallel Computing Technologies (PaCT)

作者： Lebedev, Sergey Akhmedzhanov, Dmitry Kozinov, Evgeniy Meyerov, Iosif Pirova, Anna Sysoyev, Alexander Lobachevsky State Univ Nizhni Novgorod Nizhnii Novgorod Russia

ISBN: (纸本)9783319219097;9783319219080

This paper discusses parallelization of the computationally intensive numerical factorization phase of sparse Cholesky factorization on shared memory systems. We propose and compare two parallel algorithms based on the multifrontal method. Both algorithms are implemented in a task-based fashion employing dynamic load balance. The first algorithm associates OpenMP tasks with the nodes of an elimination tree and relies on the OpenMP scheduler. The second algorithm employs a concurrent priority queue to implement balancing. Experimental results on symmetric positive definite matrices from the University of Florida Sparse Matrix Collection show that our implementation is comparable to MUMPS and Intel MKL PARDISO in terms of performance and scaling efficiency on shared memory systems.

关键词： Sparse algebra Cholesky factorization Numerical phase Multifrontal method High performance computing dynamic parallelization Task-based parallelism

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dynamic parallelization of hydrological model simulations

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ENVIRONMENTAL MODELLING & SOFTWARE 2011年第12期26卷 1736-1746页

作者： Li, Tiejian Wang, Guangqian Chen, Ji Wang, Hao Univ Hong Kong Dept Civil Engn Hong Kong Hong Kong Peoples R China Tsinghua Univ State Key Lab Hydrosci & Engn Beijing 100084 Peoples R China

This paper introduces the development of a dynamic parallel algorithm for conducting hydrological model simulations. This new algorithm consists of a river network decomposition method and an enhanced master-slave paradigm. The decomposition method is used to divide a basin river network into a large number of subbasins, and the enhanced master-slave paradigm is adopted to realize the function of this new dynamic basin decomposition method through using the Message-Passing Interface (MPI) and C++ language. This new algorithm aims to balance computation load and then to achieve a higher speedup and efficiency of parallel computing in hydrological simulation for the river basins which are delineated by high-resolution drainage networks. This paper uses a modified binary-tree codification method developed by Li et al. (2010) to code drainage networks, and the basin width function to estimate the possible maximum parallel speedup and the associated efficiency. As a case study, with a hydrological model, the Digital Yellow River Model, this new dynamic parallel algorithm is applied to the Chabagou basin in northern China. The application results reveal that the new algorithm is efficient in the dynamic dispatching of simulation tasks to computing processes, and that the parallel speedup and efficiency are comparable with the estimations made by using the basin width function. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Basin width function Digital drainage network Domain decomposition dynamic parallelization Master-slave paradigm Modified binary-tree codification

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dynamic and Speculative Polyhedral parallelization Using Compiler-Generated Skeletons

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INTERNATIONAL JOURNAL OF PARALLEL PROGRAMMING 2014年第4期42卷 529-545页

作者： Jimborean, Alexandra Clauss, Philippe Dollinger, Jean-Francois Loechner, Vincent Caamano, Juan Manuel Martinez Uppsala Univ UPMARC Uppsala Sweden Univ Strasbourg CNRS ICube INRIA Strasbourg France

We propose a framework based on an original generation and use of algorithmic skeletons, and dedicated to speculative parallelization of scientific nested loop kernels, able to apply at run-time polyhedral transformations to the target code in order to exhibit parallelism and data locality. Parallel code generation is achieved almost at no cost by using binary algorithmic skeletons that are generated at compile-time, and that embed the original code and operations devoted to instantiate a polyhedral parallelizing transformation and to verify the speculations on dependences. The skeletons are patched at run-time to generate the executable code. The run-time process includes a transformation selection guided by online profiling phases on short samples, using an instrumented version of the code. During this phase, the accessed memory addresses are used to compute on-the-fly dependence distance vectors, and are also interpolated to build a predictor of the forthcoming accesses. Interpolating functions and distance vectors are then employed for dependence analysis to select a parallelizing transformation that, if the prediction is correct, does not induce any rollback during execution. In order to ensure that the rollback time overhead stays low, the code is executed in successive slices of the outermost original loop of the nest. Each slice can be either a parallel version which instantiates a skeleton, a sequential original version, or an instrumented version. Moreover, such slicing of the execution provides the opportunity of transforming differently the code to adapt to the observed execution phases, by patching differently one of the pre-built skeletons. The framework has been implemented with extensions of the LLVM compiler and an x86-64 runtime system. Significant speed-ups are shown on a set of benchmarks that could not have been handled efficiently by a compiler.

关键词： Algorithmic skeletons Polytope model Automatic parallelization Speculative parallelization dynamic parallelization Loop nests Compilation

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The Effects of Parameter Tuning in Software Thread-Level Speculation in JavaScript Engines

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ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION 2014年第4期11卷 46-46页

作者： Martinsen, Jan Kasper Grahn, Hakan Isberg, Anders Blekinge Inst Technol Dept Comp Sci & Engn SE-37179 Karlskrona Sweden Sony Mobile Commun AB SE-22188 Lund Sweden

JavaScript is a sequential programming language that has a large potential for parallel execution in Web applications. Thread-level speculation can take advantage of this, but it has a large memory overhead. In this article, we evaluate the effects of adjusting various parameters for thread-level speculation. Our results clearly show that thread-level speculation is a useful technique for taking advantage of multicore architectures for JavaScript in Web applications, that nested speculation is required in thread-level speculation, and that the execution characteristics of Web applications significantly reduce the needed memory, the number of threads, and the depth of our speculation.

关键词： Design Languages Performance Experimentation Web applications multithreading speculative execution dynamic parallelization virtual machines

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Monte Carlo simulation on heterogeneous distributed systems: A computing framework with parallel merging and checkpointing strategies

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FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF ESCIENCE 2013年第3期29卷 728-738页

作者： Camarasu-Pop, Sorina Glatard, Tristan da Silva, Rafael Ferreira Gueth, Pierre Sarrut, David Benoit-Cattin, Hugues Univ Lyon 1 CREATIS CNRS UMR5220 Inserm U1044INSA Lyon F-69622 Villeurbanne France

This paper introduces an end-to-end framework for efficient computing and merging of Monte Carlo simulations on heterogeneous distributed systems. Simulations are parallelized using a dynamic load-balancing approach and multiple parallel mergers. Checkpointing is used to improve reliability and to enable incremental results merging from partial results. A model is proposed to analyze the behavior of the proposed framework and help tune its parameters. Experimental results obtained on a production grid infrastructure show that the model fits the real makespan with a relative error of maximum 10%, that using multiple parallel mergers reduces the makespan by 40% on average, that checkpointing enables the completion of very long simulations and that it can be used without penalizing the makespan. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Grid computing Monte Carlo Merge Checkpointing Workflow dynamic parallelization

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Compiler and Runtime Techniques for Automatic parallelization of Sequential Applications

Compiler and Runtime Techniques for Automatic Parallelizatio...

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作者： Mehrara, Mojtaba University of Michigan

学位级别：Ph.D.

Multicore designs have emerged as the mainstream design paradigm for the microprocessor industry. Unfortunately, providing multiple cores does not directly translate into performance for most applications. An attractive approach for exploiting multiple cores is to rely on tools, both compilers and runtime optimizers, to automatically extract threads from sequential applications. This dissertation tackles many challenges faced in automatic parallelization of sequential applications, including general-purpose applications written in C/C++ and client-side web applications written in JavaScript, with the goal of achieving speedup on commodity multicore systems. First, a complete parallelizing compiler system for C/C++ is introduced. This system successfully identifies parallelization opportunities in programs and transforms the code to a parallel version. A matching runtime system, STMlite, is proposed to monitor the parallelized program behavior and fix any misspeculations that might happen. We show that this system can generate and execute parallel programs that are upto 2.2x faster than their sequential counterparts, when executed on an 8-core commodity system. The second piece of work focuses on a similar problem in a very different application domain, JavaScript programs running on the client's web browser. This dissertation is the first research work that proposes dynamic and automatic parallelization of JavaScript applications. The nature of the JavaScript language and its target execution environments impose a completely different set of challenges that we intend to solve. We first propose the ParaScript parallelizing engine, which identifies and speculatively parallelizes potentially parallel code segments while the code is running in the browser. A low-cost and highly customized speculation approach verifies the execution of the parallelized client-side code and rolls back in case of any misspeculation. dynamic parallelization using ParaScript yields an averag

关键词： Speculative parallelization Software Transactional Memory JavaScript parallelization Multicore Compilation dynamic parallelization Loop Level Parallelism Thesis

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Mostly Static Program Partitioning of Binary Executables

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ACM TRANSACTIONS ON PROGRAMMING LANGUAGES AND SYSTEMS 2009年第5期31卷 17:1-17:46页

作者： Yardimci, Efe Franz, Michael Univ Calif Irvine Irvine CA 92717 USA

We have built a runtime compilation system that takes unmodified sequential binaries and improves their performance on off-the-shelf multiprocessors using dynamic vectorization and loop-level parallelization techniques. Our system, Azure, is purely software based and requires no specific hardware support for speculative thread execution, yet it is able to break even in most cases;that is, the achieved speedup exceeds the cost of runtime monitoring and compilation, often by significant amounts. Key to this remarkable performance is an offline preprocessing step that extracts a mostly correct control flow graph (CFG) from the binary program ahead of time. This statically obtained CFG is incomplete in that it may be missing some edges corresponding to computed branches. We describe how such additional control flow edges are discovered and handled at runtime, so that an incomplete static analysis never leads to an incorrect optimization result. The availability of a mostly correct CFG enables us to statically partition a binary executable into single-entry multiple-exit regions and to identify potential parallelization candidates ahead of execution. Program regions that are not candidates for parallelization can thereby be excluded completely from runtime monitoring and dynamic recompilation. Azure's extremely low overhead is a direct consequence of this design.

关键词： Design Experimentation Performance Continuous compilation and optimization dynamic parallelization binary translation

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