A Survey of Parallel Programming Constructs

This paper surveys the types of parallelism found in Functional, Lisp and Object-Oriented languages. In particular, it concentrates on the addition of high level parallel constructs to these types of languages. The traditional area of the automatic extraction of parallelism by a compiler [39] is ignored here in favor of the addition of new constructs, because the long history of such automatic techniques has shown that they are not sufficient to allow the massive parallelism promised from modem computer architectures [26. 58]. The problem then, simply stated, is given that it is now possible for us to build massively parallel machines and given that our current compilers seem incapable of generating sufficient parallelism automatically, what should the language designer do? A reasonable answer seems to be to add constructs to languages that allow the expression of additional parallelism in a natural way. Indeed that is what the designers of the the Functional, Lisp, and Object-Oriented languages described below have attempted to do. The three particular programming formalisms were picked because most of the initial ideas seem to have been generated by the designers of the functional languages and most of the current activity seems to be in the Lisp and Objected-Oriented domains. There is also a great deal of activity in the Logic programming area, but this activity is more in the area of executing the existing constructs in parallel as opposed to adding constructs specifically designed to increase parallelism