Synchronization of asynchronous processes in CSP

Abstract

Many concurrent programming languages including CSP and Ada use synchronous message-passing to define communication between a pair of asynchronous processes. Suggested primitives like the generalized alternative command for CSP and the symmetric select statement for Ada allow a process to nondeterministically select one of several communication statements for execution. The communication statement may be either an input or an output statement. We propose a simple algorithm to implement the generalized alternative command and show that it uses fewer messages than existing algorithms.