Coalition threading: combining traditional andnon-traditional parallelism to maximize scalability

  • Authors:

  • Md Kamruzzaman;Steven Swanson;Dean M. Tullsen

  • Affiliations:

  • University of California, San Diego, La Jolla, CA, USA;University of California, San Diego, La Jolla, CA, USA;University of California, San Diego, La Jolla, CA, USA

  • Venue:
  • Proceedings of the 21st international conference on Parallel architectures and compilation techniques
  • Year:
  • 2012

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Abstract

Non-traditional parallelism provides parallel speedup for a single thread without the need to manually divide and coordinate computation. This paper describes coalition threading, a technique that seeks the ideal combination of traditional and non-traditional threading to make the best use of available hardware parallelism. Coalition threading provides up to 2x gains over traditional parallel techniques on individual loops. However, deciding when and to what degree to apply either traditional or non-traditional threading is a difficult decision. This paper provides heuristics for identifying loops that benefit from a combination of traditional and non-traditional parallelism and those that will perform best with a single technique. Using this heuristic, coalition threading provides an average gain of 17% across all the loops and an average speedup of 16.7% for the full applications over traditional parallelism. This performance is within 0.7% of the speedup that an oracle heuristic could attain.