Early Experiments with the OpenMP/MPI Hybrid Programming Model

The paper describes some very early experiments on new architectures that support the hybrid programming model. Our results are promising in that OpenMP threads interact with MPI as desired, allowing 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 hybrid program and illustrate that a hybrid computation might not always proceed as expected.