Effective cross-platform, multilevel parallelism via dynamic adaptive execution

This paper presents preliminary efforts to develop compilation and execution environments that achieve performance portability of multilevel parallelization on hierarchical architectures. Using the NAS parallel benchmarks, we first illustrate the lack of portable performance on stateof- the-art scalable parallel systems despite the use of two portable programming models, MPI and OpenMP. Then we present a dynamic compilation and execution framework that provides the desired portability through the use of program slices. These slices are used to select the optimal program decomposition on each architecture. Currently, our framework uses a simple incremental algorithm, which effectively identifies single or multi-level program decompositions that maximize performance. This algorithm can be used as a rule of thumb for automatic multilevel parallelization. The effectiveness of the approach is demonstrated on the NAS benchmarks running on two architectural platforms.