Paper Details

Java Threads in Light of occam/CSP (Tutorial)

Authors: Welch, Peter H.

Abstract:

Java provides support for parallel computing through a model that is built into the language itself. However, the designers of Java chose to be fairly conservative and settled for the contepts of threads and monitors. Monitors were developed by Tony Hoare in the early 1970s as a structued way of using semaphores to control access to shared resources. Hoare moved away from this, in the late 1970s, to develop the theory of Communicating Processes (CSP). One reason for this was that the semantics of monitors and threads are not WYSIWIG, so that designing robust parallel algorithms at this level is seriously hard. Fortunately, it is possible to introduce the CSP model into Java through sets of classes implemented on top of its monitor support. By restricting interaction between active Java objects to CSP synchronisation primitives, Jav thread semantics become compositional and systems with arbitrary levels of complexity become possible. Multi-threaded Web applets and distributed applications become simpler to design and implement, race hazards never occured, difficulties such as starvation, deadlock and livelock are easier to confront and overcome, and performance is no worse than that obtained from directly using the raw monitor primitives. The advantages of teaching parallelism in Java purely through the CSP class libraries will be discussed. (These libraries were developed jointly at Kent and Oxford Universities in the UK and the University of Twente in the Netherlands.)

Proceedings:

Proceedings of WoTUG-20: Parallel Programming and Java, André W. P. Bakkers, 1997, pp 282 - 282 published by IOS Press, Amsterdam

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