Task Computability in Unreliable Anonymous Networks

Authors Petr Kuznetsov, Nayuta Yanagisawa

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Petr Kuznetsov
  • LTCI, Télécom ParisTec, Université Paris-Saclay, France
Nayuta Yanagisawa
  • DeNA Co., Ltd., Japan

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Petr Kuznetsov and Nayuta Yanagisawa. Task Computability in Unreliable Anonymous Networks. In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, pp. 23:1-23:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


We consider the anonymous broadcast model: a set of n anonymous processes communicate via send-to-all primitives. We assume that underlying communication channels are asynchronous but reliable, and that the processes are subject to crash failures. We show first that in this model, even a single faulty process precludes implementations of atomic objects with non-commuting operations, even as simple as read-write registers or add-only sets. We, however, show that a sequentially consistent read-write memory and add-only sets can be implemented t-resiliently for t<n/2, i.e., provided that a majority of the processes do not fail. We use this implementation to establish an equivalence between the t-resilient read-write anonymous shared-memory model and the t-resilient anonymous broadcast model in terms of colorless task solvability. As a result, we obtain the first task computability characterization for unreliable anonymous message-passing systems.

Subject Classification

ACM Subject Classification
  • Theory of computation → Distributed computing models
  • Theory of computation → Computability
  • Distributed tasks
  • anonymous broadcast
  • fault-tolerance


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