Deterministic OpenMP

Deterministic OpenMP Amittai F. Aviram 2012 Researchers widely agree that determinism in parallel programs is desirable. Although experimental parallel programming languages have long featured deterministic semantics, in mainstream parallel environments, developers still build on nondeterministic constructs such as mutexes, leading to timeor schedule-dependent heisenbugs. To make deterministic programming more accessible, we introduce DOMP, a deterministic extension to OpenMP, preserving the familiarity of traditional languages such as C and Fortran, and maintaining source-compatibility with much of the existing OpenMP standard. Our analysis of parallel idioms used in 35 popular benchmarks suggests that the idioms used most often (89% of instances in the analyzed code) are either already expressible in OpenMP’s deterministic subset (74%), or merely lack more general reduction (12%) or pipeline (3%) constructs. DOMP broadens OpenMP’s deterministic subset with generalized reductions, and implements an efficient deterministic runtime that acts as a drop-in replacement for Gnu’s widely used conventional OpenMP support library GOMP, on mainstream Unix platforms. We evaluate DOMP with several existing OpenMP benchmarks, each requiring under 50 source line changes and a majority requiring none, as well as several benchmarks we ported to OpenMP/DOMP. We find DOMP’s efficiency and scalability comparable to GOMP in 7 of 11 benchmarks, suggesting that a deterministic model for mainstream parallel programming may be well within reach. Deterministic OpenMP A Dissertation Presented to the Faculty of the Graduate School of Yale University in Candidacy for the Degree of Doctor of Philosophy by Amittai F. Aviram Dissertation Director: Bryan A. Ford