Investigating the Performance of Two Programming Models for Clusters of Commodity Smp

Multiprocessors and high performance networks allow to build CLUsters of MultiProcessors (CLUMPs). A main 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 2-way SMP PCs connected by a Myrinet network for NAS benchmarks from two programming: a Single Memory Model based on the MPICH-PM/CLUMP library of the RWCP and a Hybrid Memory Model using MPICH-PM and OpenMP. We compare 2-way SMP conngurations speed-up versus single CPU conngurations for each model. We demonstrate that better model depends on the features of the applications. In particular, we detail the speed-up results from breakdowns of the benchmarks execution times and from measurements of hardware counters. Then, we show that these two models give performance for PC based CLUMPs close to performance of scalable high-end multicomputers up to large con-gurations (36 nodes).