MPI versus MPI+OpenMP on the IBM SP for the NAS benchmarks

Franck Cappello, Daniel Etiemble

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The hybrid memory model of clusters of multiprocessors raises two issues: programming model and performance. Many parallel programs have been written by using the MPI standard. To evaluate the pertinence of hybrid models for existing MPI codes, we compare a unified model (MPI) and a hybrid one (OpenMP fine grain parallelization after profiling) for the NAS 2.3 benchmarks on two IBM SP systems. The superiority of one model depends on 1) the level of shared memory model parallelization, 2) the communication patterns and 3) the memory access patterns. The relative speeds of the main architecture components (CPU, memory, and network) are of tremendous importance for selecting one model. With the used hybrid model, our results show that a unified MPI approach is better for most of the benchmarks. The hybrid approach becomes better only when fast processors make the communication performance significant and the level of parallelization is sufficient.

Original languageEnglish (US)
Title of host publicationSC 2000 - Proceedings of the 2000 ACM/IEEE Conference on Supercomputing
PublisherAssociation for Computing Machinery
ISBN (Electronic)0780398025
StatePublished - 2000
Externally publishedYes
Event2000 ACM/IEEE Conference on Supercomputing, SC 2000 - Dallas, United States
Duration: Nov 4 2000Nov 10 2000

Publication series

NameProceedings of the International Conference on Supercomputing


Conference2000 ACM/IEEE Conference on Supercomputing, SC 2000
Country/TerritoryUnited States

ASJC Scopus subject areas

  • General Computer Science


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