In the previous chapter, we presented a conservative simulation protocol for message passing parallel programs that uses a conjunction of the conditional event and the null message protocols, and incorporates the optimizations mentioned in Chapter 3. In this chapter, we present the implementation and evaluation of this protocol for MPI[MPI93] programs. The implementation is in the form of a library for a subset of MPI, called MPISIM. An existing MPI program can be linked with little or automatic modification to MPISIM instead of MPI, resulting in a multithreaded simulator for the target MPI program. The simulator executes using one processor or a few processors in parallel, and predicts the performance of the target MPI program.
The rest of this chapter is organized as follows: the following section contains a brief description of the subset of MPI implemented in MPISIM. Section 5.3 describes the MPI simulation model and its implementation. Section 5.4 contains a description of the software used to execute a simulator that uses MPISIM. Section 5.5 presents results for the validation and performance of MPISIM for the the NAS Parallel Benchmarks (NPB 2.0)[NAS95]. Section 5.6 contains a brief conclusion.