Centre de Recherche en Informatique, Ecole des mines de Paris,

Applications with varying array access patterns require to dynamically change array mappings on distributed-memory parallel machines. Hpf (High Performance Fortran) provides such remappings, on data that can be replicated, explicitly through the realign and redistribute directives and implicitly at procedure calls and returns. However such features are left out of the hpf subset or of the currently discussed hpf kernel for eciency reasons. This paper presents a new compilation technique to handle hpf remappings for message-passing parallel architectures. The rst phase is global and removes all useless remappings that appear naturally in procedures. The code generated by the second phase takes advantage of replications to shorten the remapping time. It is proved optimal: A minimal number of messages, containing only the required data, is sent over the network. The technique is fully implemented in hpfc, our prototype hpf compiler. Experiments were performed on a Dec Alpha farm. Keywords: Hpf compilation, array remappings, redistributions, distributed-memory mimd architecture, message-passing, pvm, static load-balancing, linear algebra, polyhedrons, constraint-based code generation