Runtime Support and Compilation Methods for User-Specified Data Distributions

This paper describes two new ideas by which an HPF compiler can deal with irregular computations effectively. The first mechanism invokes a user-specified parallel mapping procedure via a set of compiler directives. The directives allow use of program arrays to describe graph connectivity, spatial location of array elements and computational load. The second mechanism is a simple conservative method that in many cases enables a compiler to recognize that it is possible to reuse previously computed information from inspectors (e.g. communication schedules, loop iteration partitions, information that associates off-processor data copies with on-processor buffer locations). We present performance results for these mechanisms from a Fortran 90D compiler implementation. This work was sponsored in part by ARPA (NAG-1-1485), NSF (ASC 9213821) and ONR (SC292-1-22913). Also supported by NASA Contract No. NAS1-19480 while author Saltz was in residence at ICASE, NASA Langley Research Center, H..