Runtime dependence computation and execution of loops on heterogeneous systems

Anantpur, Jayvant and Govindarajan, R (2013) Runtime dependence computation and execution of loops on heterogeneous systems. In: 2013 IEEE/ACM International Symposium on Code Generation and Optimization (CGO), 23-27 Feb. 2013, Shenzhen, pp. 151-160.

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Abstract

GPUs have been used for parallel execution of DOALL loops. However, loops with indirect array references can potentially cause cross iteration dependences which are hard to detect using existing compilation techniques. Applications with such loops cannot easily use the GPU and hence do not benefit from the tremendous compute capabilities of GPUs. In this paper, we present an algorithm to compute at runtime the cross iteration dependences in such loops. The algorithm uses both the CPU and the GPU to compute the dependences. Specifically, it effectively uses the compute capabilities of the GPU to quickly collect the memory accesses performed by the iterations by executing the slice functions generated for the indirect array accesses. Using the dependence information, the loop iterations are levelized such that each level contains independent iterations which can be executed in parallel. Another interesting aspect of the proposed solution is that it pipelines the dependence computation of the future level with the actual computation of the current level to effectively utilize the resources available in the GPU. We use NVIDIA Tesla C2070 to evaluate our implementation using benchmarks from Polybench suite and some synthetic benchmarks. Our experiments show that the proposed technique can achieve an average speedup of 6.4x on loops with a reasonable number of cross iteration dependences.

Item Type:	Conference Paper
Series.:	International Symposium on Code Generation and Optimization
Publisher:	IEEE
Additional Information:	Copyright of this article belongs to IEEE.
Keywords:	Algorithms; Languages; Performance
Department/Centre:	Division of Interdisciplinary Sciences > Supercomputer Education & Research Centre
Date Deposited:	23 Jun 2013 09:30
Last Modified:	23 Jun 2013 09:30
URI:	http://eprints.iisc.ac.in/id/eprint/46765

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