Chunking parallel loops in the presence of synchronization
Jun Shirako, Jisheng M. Zhao, V. Krishna Nandivada, Vivek Sarkar · 2009
Modern languages for shared-memory parallelism are moving from a bulk-synchronous Single Program Multiple Data (SPMD) execution model to lightweight Task Parallel execution models for improved productivity. This shift is intended to encourage programmers to express the ideal parallelism in an application at a fine granularity that is natural for the underlying domain, while delegating to the compiler and runtime system the job of extracting coarser-grained useful parallelism for a given target system. A simple and important example of this separation of concerns between ideal and useful parallelism can be found in chunking of parallel loops, where the programmer expresses ideal parallelism by declaring all iterations of a loop to be parallel and the implementation exploits useful parallelism by executing iterations of the loop in sequential chunks.