Eecient Support for Multiple Concurrency Paradigms in Modern Programming Languages

We describe an approach to implementing a wide-range of concurrency paradigms in modern programming languages. The focus of our discussion is sting, a dialect of Scheme, that supports lightweight threads of control and virtual processors as rst-class objects. Given the signiicant degree to which the behavior of these objects may be customized, we can easily express a variety of concurrency paradigms and linguistic structures within a common framework without loss of eeciency. Sting is thus intended to be used as an operating system substrate for modern parallel programming languages. Unlike parallel systems that rely on low-level operating system services for managing concurrency, sting implements concurrency management entirely in terms of Scheme objects and procedures. It, therefore, permits users to optimize the runtime behavior of their applications without requiring knowledge of the underlying runtime system. This paper concentrates on (a) the implications of the design for building asynchronous con-currency structures, (b) the implementation of a thread controller using continuations as its basic control mechanism, (c) the organization of large-scale concurrent computations, and (d) robust programming environments for symbolic computing.