Specification and Development of Parallelalgorithms with the Proteus

The Proteus language is a wide-spectrum parallel programming notation that supports the expression of both high-level architecture-independent speciications and lower-level architecture-speciic implementations. A methodology based on successive reenement and interactive experimentation supports the development of parallel algorithms from speciication to various eecient architecture-dependent implementations. The Proteus system combines the language and tools supporting this methodology. This paper presents a brief overview of the Proteus system and describes its use in the exploration and development of several non-trivial algorithms, including the fast multipole algorithm for N-body computations. 1. Introduction Practical implementations of parallel algorithms that access the performance potential of current computers are diicult to develop, too often fail to deliver the expected performance, and lack portability to other platforms. This state of aaairs may be explained by the proliferation of parallel architectures and the simultaneous lack of eeective high-level architecture-independent programming languages. Parallel applications are currently developed using low-level parallel programming notations that reeect speciic features of the target architecture (e.g., shared vs. distributed memory, SIMD vs. MIMD, exposed vs. hidden interconnection network). These notations lack portability across architectures and are too low-level to support the exploration of complex designs. Higher-level notations, on the other hand, trade reduced access to architecture-speciic features for improved abstract models of computation, but this trade is often not the right one: the whole point of parallelism, for most applications, is performance. The problem is a fundamental one: abstract models of parallel computation lead to impractical implementations, whereas machine-speciic models lead to intractable analysis of even the simplest programs. The goal of our work is to provide tools for exploring the design space of a parallel application by a process of prototyping and successive reenement. The Proteus system comprises: