Parallelization in the Presence of Generalized Induction and Reduction Variables

Abstract

The elimination of induction variables and the parallelization of reductions in FORTRAN programs has been shown to be integral to performance improvement on parallel computers [9, 10]. As part of the Polaris project, compiler passes that recognize these idioms have been implemented and evaluated. Developing these techniques to the point necessary for achieving significant speedups on real applications has prompted solutions to problems that have not been addressed in previous reports. These include analysis capabilities to disprove zero-trip loops, symbolic handling facilities to compute closed forms of recurrences, and interfaces to other compilation passes, such as the datadependence test. In comparison, the analysis phase of induction variables, which has received most attention so far, has turned out to be relatively straightforward. 1 Introduction The parallelization of loops requires resolution of many types of data dependences ([2], [5], [17]). In particular, cross-iteration de..