Abstract
The problem of allowing a dynamically changing set of processes fair access to a shared resource is considered, in the context of communication-stream based systems. It is argued that fair binary merge operators alone cannot solve this problem satisfactorily. Two solutions are proposed. One employs binary merge operators with a programmable bias; the other binary and ternary fair merge operators capable of self-balancing, using the concept of 2–3 trees. A Concurrent Prolog implementation of these operators is described. The implementation of the self-balancing merge operators illustrates the expressive power of incomplete messages, a programming technique that supports messages that contain communication channels as arguments. In the course of implementing the self-balancing merge operator, it was necessary to develop a distributed variant of the 2–3 tree deletion algorithm.
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This is a revised and extended version of the paper presented at the 1984 International Symposium on Logic Programming, Atlantic City. U. S. A., February 1984.
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Shapiro, E., Mierowsky, C. Fair, biased, and self-balancing merge operators: Their specification and implementation in Concurrent Prolog. NGCO 2, 221–240 (1984). https://doi.org/10.1007/BF03037058
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DOI: https://doi.org/10.1007/BF03037058