Parallel object-oriented descriptions of graph reduction machines

Abstract

Abstract machine descriptions of parallel computer architectures must capture communications and concurrency characteristics at a high level. Current design techniques and notations are weak in this respect. We present a layered method for refinement of a requirements specification through to a detailed systems architecture design. This paper concentrates on the two highest layers, the logical model, which is a requirements statement, and the systems architecture, which specifies logical processes and explicit communications. While requirements are expressed in a language that matches the problem domain, we suggest that a parallel object-oriented notation is most appropriate for the systems architecture layer. Refinements within this layer reflect implementation details (eg. structure sharing and distribution of work among processing elements). We introduce a parallel object-oriented notation based on rewriting systems concepts and use it to refine the design of a parallel graph reduction machine to execute functional programs. The notation used is a natural extension of a graph rewriting language and the work forms the basis for a structured explication of parallel graph rewriting in which all communications are made explicit.