Contention in shared memory algorithms
Journal of the ACM (JACM)
Public data structures: counters as a special case
Theoretical Computer Science
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Abstract: This paper deals with concurrent counters which are built from RMW bits, and count modulo 2/sup k/ (for any k/spl isin//spl Nscr/). A counter supports two operations: increment and look. A counter is dynamic if every look operation L returns a value between the number of increments ended before L started and the number of increments started until L ended. A counter is public if it can be accessed by an unbounded number of processes. It was conjectured that there exists no public dynamic counter modulo 2/sup k/ for k1. In this paper we refute this conjecture by showing an efficient dynamic counter modulo 2/sup k/ for any k. Our construction is also more efficient than previous constructions that assume an apriori known bound on the number of processes or increment operations. We show how our construction can be used to build an entrance protocol for any counting network to yield a dynamic counting network (a counting network that supports dynamic look). Our transformation preserves the time complexity and the contention of the original counting network. Since it was shown that there exists no linearizable counting network, dynamic counting seems to be the strongest condition one can impose on a counting network.