Communication Characteristics and Hybrid MPI/OpenMP Parallel Pr ogramming on Clusters of Multi-core SMP Nodes
Georg Hager, Gabriele Jost, Rolf Rabenseifner · 2009
Hybrid MPI/OpenMP and pure MPI on clusters of multicore SMP nodes involve several mismatch problems between the parallel programming models and the hardware architectures. Measurements of communication characteristics between cores on the same socket, on the same SMP node, and between SMP nodes on several platforms (including Cray XT4 and XT5) show that machine topology has a significant impact on performance for all parallelization strategies and that topology awareness should be built into all applications in the future. We describe potentials and challenges of the dominant programming models on hierarchically structured hardware. Case studies with the multizone NAS parallel benchmarks on several platforms demonstrate the opportunities of hybrid programming.