Abstract
Are randomized consensus algorithms more powerful than deterministic ones? Seemingly so, since randomized algorithms exist that reach consensus in expected constant number of rounds, whereas the deterministic counterparts are constrained by the r ≥ t + 1 lower bound in the number of communication rounds, where t is the maximum number of faults to be tolerated.
In this paper, however, we study the behavior of deterministic algorithms when consensus is repeatedly needed, say k times. We show that it is possible to achieve consensus with the optimal number of processors (n > 3t), and optimal amortized cost in all other measures: the number of communication rounds r*, the maximal message size m*, and the total bit complexity b*.
More specifically, we achieve the following amortized bounds for k consensus instances: r*=O(1 + t/k), b*=O(t2 + t1/k), and m*=O(1 + t2/k). When k ≥ t2, then r* and m* are O(1) and b*=O(t2) which is optimal.
Work of second and fourth authors partially supported by the NSERC (Natural Sciences and Engineering Research Council of Canada) International Postdoctoral Fellowship and research grants from the NSERC and the Advanced Systems Institute of British Columbia.
This work was carried out while this author was at the School of Computing Science, Simon Fraser University.
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© 1992 Springer-Verlag Berlin Heidelberg
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Bar-Noy, A., Deng, X., Garay, J.A., Kameda, T. (1992). Optimal amortized distributed consensus. In: Toueg, S., Spirakis, P.G., Kirousis, L. (eds) Distributed Algorithms. WDAG 1991. Lecture Notes in Computer Science, vol 579. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0022440
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DOI: https://doi.org/10.1007/BFb0022440
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