Parallel performance study of Monte Carlo photon transport code on shared-, distributed-, and distributed-shared-memory architectures

We have parallelized a Monte Carlo photon transport algorithm. Three different parallel versions of the algorithm were developed. The first version is for the Tera Multi-Threaded Architecture (MTA) and uses Tera specific directives. The second version, which uses MPI library calls, has been implemented on both the CRAY T3E and the 8-way SMP IBM SP with Power3 processors. The third version is a hybrid MPI-OpenMP implementation and is used on the SMP IBM SP. This version uses MPI to communicate between nodes and OpenMP to perform shared memory operations among processors within a node. We explain the three different parallelization approaches and present parallel performance results of these three parallel implementations on three different machines. We observe near perfect speedup for the three versions on the three architectures. The results on the SMP IBM SP suggest that the hybrid MPI-OpenMP programming is suitable for SMP type machines.