PARALLEL PROGRAMS.

Abstract

Parallel programs have several advantages over the conventional sequential programs. They can be extremely simple and comprehensible, and offer possibilities for more efficient execution. A parallel program consists of various largely independent processes that have to be synchronized at some points. It may be necessary, for example, to ensure that certain parts of different processes are never executed at the same time. Synchronization is achieved by means of special operations on special variables (e. g. the P-operation and the V-operation on semaphores). In the design of parallel programs particular problems arise, such as the avoidance of situations in which certain processes remain permanently waiting for one another ('deadlock'), or in which some processes never receive a turn ('individual starvation'). The development of techniques for preventing such situations from arising is an important area of research.