Compiling affine loop nests for distributed-memory parallel architectures

Abstract

We present new techniques for compilation of arbitrarily nested loops with affine dependences for distributed-memory parallel architectures. Our framework is implemented as a source-level transformer that uses the polyhedral model, and generates parallel code with communication expressed with the Message Passing Interface (MPI) library. Compared to all previous approaches, ours is a significant advance either (1) with respect to the generality of input code handled, or (2) efficiency of communication code, or both. We provide experimental results on a cluster of multicores demonstrating its effectiveness. In some cases, code we generate outperforms manually parallelized codes, and in another case is within 25% of it. To the best of our knowledge, this is the first work reporting end-to-end fully automatic distributed-memory parallelization and code generation for input programs and transformation techniques as general as those we allow.