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The choice coordination problem


In the course of a concurrent computation, processes P1,..., Pn must reach a common choice of one out of k alternatives A 1,..., A k. They do this by protocols using k shared variables, one for each alternative. If the range of the variables has m values then \(\frac{{\text{1}}}{{\text{2}}}\sqrt[{\text{3}}]{n} \leqq \operatorname{m} \) is necessary, and n + 2≦m is sufficient, for deterministic protocols solving the choice coordination problem (C.C.P.). We introduce very simple randomizing protocols which, independently of n, solve the C.C.P. by use of a fixed alphabet. A single-byte (256-valued) alphabet permits a solution with non-termination probability smaller than 2−127. Many software and hardware tasks involving concurrency can be interpreted as choice coordination problems. Choice coordination problems occur also in nature.

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This research was supported in part by NSF grants: MCS77-02474 at Washington University, Seattle, MCS80-12716 at University of California at Berkeley. Presented at the Specker Symposium in Zürich, January 1980

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Rabin, M.O. The choice coordination problem. Acta Informatica 17, 121–134 (1982).

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  • Information System
  • Operating System
  • Data Structure
  • Communication Network
  • Information Theory