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The Liberty Research Group

Decoupled Software Pipelining Creates Parallelization Opportunities [abstract] (ACM DL, PDF)
Jialu Huang, Arun Raman, Yun Zhang, Thomas B. Jablin, Tzu-Han Hung, and David I. August
Proceedings of the 2010 International Symposium on Code Generation and Optimization (CGO), April 2010.

Decoupled Software Pipelining (DSWP) is one approach to automatically extract threads from loops. It partitions loops into long-running threads that communicate in a pipelined manner via inter-core queues. This work recognizes that DSWP can also be an enabling transformation for other loop parallelization techniques. This use of DSWP, called DSWP+, splits a loop into new loops with dependence patterns amenable to parallelization using techniques that were originally either inapplicable or poorly-performing. By parallelizing each stage of the DSWP+ pipeline using (potentially) different techniques, not only is the benefit of DSWP increased, but the applicability and performance of other parallelization techniques are enhanced. This paper evaluates DSWP+ as an enabling framework for other transformations by applying it in conjunction with DOALL, LOCALWRITE, and SpecDOALL to individual stages of the pipeline. This paper demonstrates significant performance gains on a commodity 8-core multicore machine running a variety of codes transformed with DSWP+.