Investigating the performance of two programming models for clusters of SMP PCs

Multiprocessors and high performance networks allow building CLUsters of MultiProcessors (CLUMPs). One distinctive feature over traditional parallel computers is their hybrid memory model (message passing between the nodes and shared memory inside the nodes). We evaluate the performance of a cluster of dual processor PCs connected by a Myrinet network for NAS benchmarks using two programming models: a Single Memory Model based on the MPICH-PM/CLUMP library of the RWCP and a Hybrid Memory Model using MPICH-PM and OpenMP. MPI programs are used as the reference in all experiments involving programming models. We compare dual processor node configurations speedup versus uniprocessor node configurations for each model. We demonstrate that the superiority of one model over the other depends on the features of the applications. In particular, we detail the speedup results from breakdowns of the benchmark execution times and from measurements of hardware counters.