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On maximum achievable speeds for field solvers

On maximum achievable speeds for field solvers Purpose – Prompted by the empirical evidence that achievable flow solver speeds for large problems are limited by what appears to be a time of the order of O(0.1) sec/timestep regardless of the number of cores used, the purpose of this paper is to identify why this phenomenon occurs. Design/methodology/approach – A series of timing studies, as well as in-depth analysis of memory and inter-processors transfer requirements were carried out for a typical field solver. The results were analyzed and compared to the expected performance. Findings – The analysis shows that at present flow speeds per core are already limited by the achievable transfer rate to RAM. For smaller domains/larger number of processors, the limiting speed of CFD solvers is given by the MPI communication network. Research limitations/implications – This implies that at present, there is a “limiting useful size” for domains, and that there is a lower limit for the time it takes to update a flowfield. Practical implications – For practical calculations this implies that the time required for running large-scale problems will not decrease markedly once these applications migrate to machines with hundreds of thousands of cores. Originality/value – This is the first time such a finding has been reported in this context. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Journal of Numerical Methods for Heat and Fluid Flow Emerald Publishing

On maximum achievable speeds for field solvers

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References (10)

Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0961-5539
DOI
10.1108/HFF-01-2013-0016
Publisher site
See Article on Publisher Site

Abstract

Purpose – Prompted by the empirical evidence that achievable flow solver speeds for large problems are limited by what appears to be a time of the order of O(0.1) sec/timestep regardless of the number of cores used, the purpose of this paper is to identify why this phenomenon occurs. Design/methodology/approach – A series of timing studies, as well as in-depth analysis of memory and inter-processors transfer requirements were carried out for a typical field solver. The results were analyzed and compared to the expected performance. Findings – The analysis shows that at present flow speeds per core are already limited by the achievable transfer rate to RAM. For smaller domains/larger number of processors, the limiting speed of CFD solvers is given by the MPI communication network. Research limitations/implications – This implies that at present, there is a “limiting useful size” for domains, and that there is a lower limit for the time it takes to update a flowfield. Practical implications – For practical calculations this implies that the time required for running large-scale problems will not decrease markedly once these applications migrate to machines with hundreds of thousands of cores. Originality/value – This is the first time such a finding has been reported in this context.

Journal

International Journal of Numerical Methods for Heat and Fluid Flow – Emerald Publishing

Published: Aug 26, 2014

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