Early Experiments with the OpenMP/MPI Hybrid Programming Model

Abstract. The paper describes some very early experiments on new ar-chitectures that support the hybrid programming model. Our results are promising in that OpenMP threads interact with MPI as desired, allow-ing OpenMP-agnostic tools to be used. We explore three environments: a “typical ” Linux cluster, a new large-scale machine from SiCortex, and the new IBM BG/P, which have quite different compilers and runtime systems for both OpenMP and MPI. We look at a few simple, diagnostic programs, and one “application-like ” test program. We demonstrate the use of a tool that can examine the detailed sequence of events in a hy-brid program and illustrate that a hybrid computation might not always proceed as expected.