Runtime Support and Compilation Methods for User-specified Data Distributions

This paper describes two new ideas by which an ttPF compiler can deal with irregular computations effectively. The first mechanism invokes a user specified 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 intplementalion. *This work was sponsored in part by ARPA (NAG-l-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, Hampton, Virginia. Author Choudhary was also supported by NSF Young Investigator award (CCR-9357840). The content of the inforanation does not necessarily reflect the position or tile policy of the Govemunent and no official endorsement should be ilfferred.