Flexible Language Constructs for Large Parallel Programs

The goal of the research described in this paper is to develop flexible language constructs for writing large data parallel numerical programs for distributed memory (MIMD) multiprocessors. Previously, several models have been developed to support synchronization and comnmnication. Models for global synchronization include SIMD (Single Instruction Multiple Data), SPMD (Single Program Multiple Data), and sequentim programs annotated with data distribution statements. The two primary models for communication include implicit communication based on shared memory and explicit communication based on messages. None of these models by themselves seem sufficient to permit the natural and efficient expression of the variety of algorithms that occur in large scientific computations. In this paper, we give an overview of a new language that combines many of these programming models in a clean manner. This is done in a modular fashion such that different models can be combined to support large programs. Within a module, the selection of a model depends on the algorithm and its efficiency requirements. In this paper, we give an overview of the language and discuss some of the critical implementation details. 1Both authors supported by NSF grant ASC-9015577, NSF grant CDA-8922510 and AFOSR-90-0109 2This research was supported by the National Aeronautics and Space Administration under NASA Contract Nos. NAS1-18605 and NAS1-19480 while the author was in residence at the Institute for Computer Applications in Science and Engineering (ICASE), NASA Langley Research Center, Hampton, VA 23681.