Optimizing FORTRAN-90 Programs for Data Motion on Massively Parallel Systems

This paper describes a general compiler optimization technique that reduces communication overhead for FORTRAN-90 (and High Performance FORTRAN currently being drafted) implementations on massively parallel machines. The main sources of communication, or data motion, for the parallel implementation of a FORTRAN90 program are from array assignments (using the index triplet notation and vector indexing), array operators (e.g. CSHIFT, TRANSPOSE, etc.), and array parameter passing to and from subroutines. Coupled with the variety of ways arrays can be distributed, a FORTRAN-90 implementor faces a rich space in which data motion can be organized. A model of data motion and an algebraic representation of data motion and data layout are presented. Yale Extension, a set of layout declarations for directing the compiler in distributing the data, is described. An array reference or an array operation extracted from the source FORTRAN-90 program, given a particular data layout specified in Yale E..