Alignment Analysis within the VFCSA Pragmatic Method for Supporting Data

One of the major tasks in programming distributed memory multiprocessors with state of the art parallel languages is the speciication of eecient data distribution schemes. Unfortunately , there are no optimal strategies for generating such data distributions and thus automatic support is very diicult to provide; several heuristics have been proposed to provide some support to the user. In this paper we outline the Alignment Analysis Tool which has been implemented within the Vienna Fortran Compiler VFCS. The tool is able to provide help for nding a good distribution scheme in a pragmatic and general purpose way. It automatically generates alignment proposals for the arrays accessed in a procedure and thus simpliies the data distribution problem. Based upon the fundamental work by Li & Chen and Manish Gupta, our main contributions to the alignment problem are the extension of the set of alignment preferences detected as well as the simple but powerful heuristic for weighing alignment preferences using an explicit compiler model. We furthermore developed a method that considers both aspects of the problem-the inter-and the intradimensional alignment problem-simultaneously. We can thus provide a powerful general purpose tool able to manage even large programs in acceptable time.