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Re: Java Live | January 9, 2001

Re http://developer.java.sun.com/developer/community/chat/JavaLive/2001/jl0109.html
T_Christopher: I'm not familiar with the specifics of the University of Kent's efforts, but I strongly disapprove of Occam being a model for threading. It is based on Hoare's "Communicating Sequential Processes" and connects threads through communication channels. Although it extends to distributed memory systems easily, and prevents system crashes caused by producer threads running faster than consumers, it doesn't do very much that I like to do. I really prefer handling the stuff myself. It's easy for me, and I like the flexibility. An example from the book: I have a version of Shellsort that requires sharing an array and dynamically creating runnables to process it. The communicating process structure of Occam isn't appropriate to the algorithm.

I suspect Occam is being too strongly (mis-)associated with the assertion that shared-memory models are wrong. The panelist apparently holds views against occam (and JCSP) because he only uses a shared memory model.

Earlier, the same expert had described misunderstanding or misuse of threading rather glibly:

A couple of problems are: 

1. Not using threading but trying to program around it with sequential code. It tends to get messy. 

2. Not handling the synchronization properly. It tends to work under light loads and then crash or freeze up unpredictably under heavy loads.

His approach does not inspire confidence that he is committed to dealing with the problems of race, deadlock, livelock, and starvation in a thorough way. Maybe I'll have to read his new book (http://www.sun.com/books/catalog/christopher/).


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