Abstract
OpenMP 5.0 introduces the metadirective to support selection from a set of directive variants based on the OpenMP context, which is composed of traits from active OpenMP constructs, devices, implementations or user-defined conditions. OpenMP 5.0 restricts the selection to be determined at compile time, which requires that all traits must be compile-time constants. Our analysis of real applications indicates that this restriction has its limitation, and we explore extension of user-defined contexts to support variant selection at runtime. We use the Smith-Waterman algorithm as an example to show the need for adaptive selection of parallelism and devices at runtime, and present a prototype implemented in the ROSE compiler. Given a large range of input sizes, our experiments demonstrate that one of the adaptive versions of Smith-Waterman always chooses the parallelism and device that delivers the best performance, with improvements between 20% and 200% compared to non-adaptive versions that use the other approaches.
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Acknowledgment
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and supported by the U.S. Dept. of Energy, Office of Science, Advanced Scientific Computing Research (SC-21), under contract DE-AC02-06CH11357. The manual reference codes were supported by LLNL-LDRD 18-ERD-006. LLNL-CONF-774899. This material is also based upon work supported by the National Science Foundation under Grant No. 1833332 and 1652732.
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Yan, Y., Wang, A., Liao, C., Scogland, T.R.W., de Supinski, B.R. (2019). Extending OpenMP Metadirective Semantics for Runtime Adaptation. In: Fan, X., de Supinski, B., Sinnen, O., Giacaman, N. (eds) OpenMP: Conquering the Full Hardware Spectrum. IWOMP 2019. Lecture Notes in Computer Science(), vol 11718. Springer, Cham. https://doi.org/10.1007/978-3-030-28596-8_14
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DOI: https://doi.org/10.1007/978-3-030-28596-8_14
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