Condition-Based Protocols for Set Agreement Problems

  • A. Mostéfaoui
  • S. Rajsbaum
  • M. Raynal
  • M. Roy
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2508)


A condition C is a set of input vectors to a problem. A class of conditions that allow to solve k-set agreement in spite of f crashes in an asynchronous system is identified. A k-set agreement protocol that is always safe is described: it is guaranteed to terminate when the input vector belongs to C and it always decides on at most k different values, even if the input vector does not belong to C. While there are simple solutions when f < k, it is known that the k-set agreement problem has no solution when fk. Thus, the paper identifies classes of conditions that allow to solve this problem even when fk. The paper gives evidence that these are the only conditions that allow to solve set agreement, by proving the wait-free case. Two natural concrete conditions that belong to such a class are described. Finally, a more efficient k-set agreement protocol with only linear complexity (does not use snapshots), for any C that allows to solve consensus, when kf/(n - f) + 1 is presented. This shows how to trade fault-tolerance for agreement precision using the condition based approach.


Input Vector Shared Memory Failure Detector Impossibility Result Consensus Problem 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2002

Authors and Affiliations

  • A. Mostéfaoui
    • 1
  • S. Rajsbaum
    • 2
  • M. Raynal
    • 1
  • M. Roy
    • 1
  1. 1.IRISAUniversité de RennesRennesFrance
  2. 2.HP Research LabOne Cambridge CenterCambridgeUSA

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