GENERATING MESSAGE-PASSING PROGRAMS FROM ABSTRACT SPECIFICATIONS BY PARTIAL EVALUATION

Abstract

This paper demonstrates how parallel programs with message-passing can be generated from abstract specifications embedded in the functional language MetaOCaml. The functional style permits to design parallel programs with a high degree of parameterization, so-called skeletons. Programmers who are unexperienced in parallelism can take such skeletons for a simple and safe generation of parallel applications. Since MetaOCaml also has efficient imperative features and an MPI interface, the entire program can be written in one language, without the need to use a language interface restricting the set of data objects which could be exchanged. The semantics of abstract specifications is expressed by an interpreter written in MetaOCaml. A cost model is defined by abstract interpretation of the specification. Partial evaluation of the interpreter with a specification, a feature which MetaOCaml provides, yields a parallel program. The partial evaluation process takes time on each MPI process directly before the execution of the application program, exploiting knowledge of the number of processes, the current process identifier and the communication structure. Our example is the specification of a divide-and-conquer skeleton which is used to compute the multiplication of multi-digit numbers using Karatsuba's algorithm.