What a Parallel Programming Language Has to Let You Say

Abstract

We have implemented in simulation a prototype language for the Connection Machine called CL1. CL1 is an extrapolation of serial machine programming language technology: in CL1 one programs the individual processors to perform local computations and talk to the communications network. We present details of the largest of out experiments with CL1, an interpreter for Scheme (a dialect of Lisp) that allows a large number of different Scheme programs to be run in parallel on the otherwise SIMD Connection Machine. Our aim was not to propose Scheme as a language for a Connection Machine programming, but to gain experience using CL1 to implement an interesting and familiar algorithm. Consideration of the difficulties we encountered led us to the conclusion that CL1 programs do not capture enough of the causal structure of the processes they describe. Starting from this observation, we have designed a successor language called CGL (for Connection Graph Language).