Runtime Adjustment of Parallel Nested Loops

Durán, Alejandro; Silvera, Raul; Corbalan, Julita; Labarta, Jesús

doi:10.1007/978-3-540-31832-3_12

Cited by 13 publications

(13 citation statements)

References 9 publications

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“…In the first proposal, all available parallelism is exposed to the environment and leaves the parallelization strategy to the run-time environment [15]. Instead of static parallelization, which can not take run-time conditions into account, the run-time environment seeks to minimize overhead and balance load by first exploiting as much coarse level parallelism as possible and then balance the load by exploiting fine-grained parallelism.…”

Section: Related Workmentioning

confidence: 99%

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Parallelism and Scalability in an Image Processing Application

Rasmussen

Stuart

Karlsson

2009

Int J Parallel Prog

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The recent trends in processor architecture show that parallel processing is moving into new areas of computing in the form of many-core desktop processors and multi-processor system-on-chips. This means that parallel processing is required in application areas that traditionally have not used parallel programs. This paper investigates parallelism and scalability of an embedded image processing application. The major challenges faced when parallelizing the application were to extract enough parallelism from the application and to reduce load imbalance. The application has limited immediately available parallelism and further extraction of parallelism is limited by small data sets and a relatively high parallelization overhead. Load balance is difficult to obtain due to the limited parallelism and made worse by non-uniform memory latency. Three parallel OpenMP implementations of the application are discussed and evaluated. We show that with some modifications relative speedups in excess of 9 on a 16 CPU system can be reached.

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Section: Related Workmentioning

confidence: 99%

“…Automatic run-time thread distribution for nested parallelism has previously been proposed to eliminate the need for hand optimization [15,16]. In the first proposal, all available parallelism is exposed to the environment and leaves the parallelization strategy to the run-time environment [15].…”

Section: Related Workmentioning

confidence: 99%

Parallelism and Scalability in an Image Processing Application

Rasmussen

Stuart

Karlsson

2009

Int J Parallel Prog

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“…After several contributions, an open question remained: would it be possible to avoid the programmer intervention in order to obtain the most suitable thread distribution? In this paper we propose a mechanism to do it, based on the previous works of Duran et al [7,10]. Those works introduced the facility of sampling the execution time for each branch in the outermost level of parallelism.…”

Section: Versionmentioning

confidence: 99%

Automatic thread distribution for nested parallelism in OpenMP

Durán¹,

González²,

Corbalan³

2005

Proceedings of the 19th Annual International Conference on Supercomputing

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OpenMP is becoming the standard programming model for shared-memory parallel architectures. One of its most interesting features in the language is the support for nested parallelism. Previous research and parallelization experiences have shown the benefits of using nested parallelism as an alternative to combining several programming models such as MPI and OpenMP. However, all these works rely on the manual definition of an appropriate distribution of all the available thread across the different levels of parallelism. Some proposals have been made to extend the OpenMP language to allow the programmers to specify the thread distribution. This paper proposes a mechanism to dynamically compute the most appropriate thread distribution strategy. The mechanism is based on gathering information at runtime to derive the structure of the nested parallelism. This information is used to determine how the overall computation is distributed between the parallel branches in the outermost level of parallelism, which is constant in this work. According to this, threads in the innermost level of parallelism are distributed.The proposed mechanism is evaluated in two different environments: a research environment, the Nanos OpenMP research platform, and a commercial environment, the IBM XL runtime library. The performance numbers obtained validate the mechanism in both environments and they show the importance of selecting the proper amount of parallelism in the outer level.

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“…An automatic mechanism to dynamically detect the best way to exploit the parallelism when having nested parallel loops is presented in the study [5]. This mechanism takes into account the number of threads, the size of the problem, the number of iterations in a loop and it was implemented inside the IBM XL runtime library.…”

Section: Introductionmentioning

confidence: 99%

Parallelizing nested loops on the Intel Xeon Phi on the example of the dense WZ factorization

Bylina

2016

Annals of Computer Science and Information Systems

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Abstract-In this article we evaluate some strategies of parallelizing nested loops on Intel Xeon Phi on the example of the WZ factorization for dense matrices. We employ both parallelism and vectorization to accelerate nested loops on manycore coprocessor.For random dense square matrices with the dominant diagonal we report the execution time and the performance of the nested loops. Numerical experiments show that the vectorization that is efficiently exploiting SIMD vector units do not always improve the application performance on the coprocessor.

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Runtime Adjustment of Parallel Nested Loops

Cited by 13 publications

References 9 publications

Parallelism and Scalability in an Image Processing Application

Parallelism and Scalability in an Image Processing Application

Automatic thread distribution for nested parallelism in OpenMP

Parallelizing nested loops on the Intel Xeon Phi on the example of the dense WZ factorization

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