Asynchronous Cooperative Multiprocessing Within

Existing computing systems do not permit cooperative multiprocessing, i.e. computations consisting of several concurrently operating processes which use shared data-bases actively. When all data references are fully synchronised to avoid conflict, such computation is possible; however such synchronisation is nearly impossible in existing environments.With asynchronous operation of the processes, output-functionality i.e. the property that the results of a computation are reproducible, becomes the chief consideration and also the chief problem with current systems. Several models for output-functional cooperative multiprocessing have been proposed. One of these has been chosen and a sub-system for MULTICS is proposed that ensures output-functionality of multiprocess computations. The operation of processes on segments is controlled, using the access checking mechanism, so that conflicts are avoided. Procedures for use in this control of access and for the creation and deletion of processes in a convenient manner are described. The procedures are defined in sufficient detail to permit relatively easy coding. The sub-system proposed ensures that all computations performed within that environment will have reproducible results under minimal restrictions. Multiprocessing in the sub-system requires fairly substantial computation on the part of each process for efficiency, as the access control is implemented in software. THESIS SUPERVISOR: Jack B. Dennis TITLE: Associate Professor of Electrical Engineering