Dynamic Determinacy Race Detection for Task Parallelism with Futures

Existing dynamic determinacy race detectors for task-parallel programs are limited to programs with strict computation graphs, where a task can only wait for its descendant tasks to complete. In this paper, we present the first known determinacy race detector for non-strict computation graphs, constructed using futures. The space and time complexity of our algorithm are similar to those of the classical SP-bags algorithm, when using only structured parallel constructs such as spawn-sync and async-finish. In the presence of point-to-point synchronization using futures, the complexity of the algorithm increases by a factor determined by the number of future task creation and get operations as well as the number of non-tree edges in the computation graph. The experimental results show that the slowdown factor observed for our algorithm relative to the sequential version is in the range of 1.00x-9.92x, which is in line with slowdowns experienced for strict computation graphs in past work.