An Evaluation of MPI and OpenMP Paradigms for Multi-Dimensional Data Remapping

We evaluate dynamic data remapping on cluster of SMP architectures under OpenMP, MPI, and hybrid paradigms. Traditional method of multi-dimensional array transpose needs an auxiliary array of the same size and a copy back stage. We recently developed an inplace method using vacancy tracking cycles. The vacancy tracking algorithm outperforms the traditional 2-array method as demonstrated by extensive comparisons. Performance of multi-threaded parallelism using OpenMP are first tested with different scheduling methods and different number of threads. Both methods are then parallelized using several parallel paradigms. At node level, pure OpenMP outperforms pure MPI by a factor of 2.76 for vacancy tracking method. Across entire cluster of SMP nodes, by carefully choosing thread numbers, the hybrid MPI/OpenMP implementation outperforms pure MPI by a factor of 3.79 for traditional method and 4.44 for vacancy tracking method, demonstrating the validity of the parallel paradigm of mixing MPI with OpenMP.