Analysis of Explicit vs. Implicit Tasking in OpenMP Using Kripke

Dynamic task-based parallelism has become a widely-accepted paradigm in the quest for exascale computing. In this work, we deliver a non-trivial demonstration of the advantages of explicit over implicit tasking in OpenMP 4.5 in terms of both expressiveness and performance. We target the Kripke benchmark, a mini-application used to test the performance of discrete particle codes, and find that the dependence structure of the core “sweep” kernel is well-suited for dynamic task-based systems. Our results show that explicit tasking delivers a 31.7% and 8.1% speedup over a pure implicit implementation for a small and large problem, respectively, while a hybrid variant also underperforms the explicit variant by 13.1% and 5.8%, respectively.