Computing in the Presence of Concurrent Solo Executions

  • Maurice Herlihy
  • Sergio Rajsbaum
  • Michel Raynal
  • Julien Stainer
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8392)


In a wait-free model any number of processes may crash. A process runs solo when it computes its local output without receiving any information from other processes, either because they crashed or they are too slow. While in wait-free shared-memory models at most one process may run solo in an execution, any number of processes may have to run solo in an asynchronous wait-free message-passing model.

This paper is on the computability power of models in which several processes may concurrently run solo. It first introduces a family of round-based wait-free models, called the d-solo models, 1 ≤ d ≤ n, where up to d processes may run solo. The paper gives then a characterization of the colorless tasks that can be solved in each d-solo model. It also introduces the (d,ε)-solo approximate agreement task, which generalizes ε-approximate agreement, and proves that (d,ε)-solo approximate agreement can be solved in the d-solo model, but cannot be solved in the (d + 1)-solo model. The paper studies also the relation linking d-set agreement and (d,ε)-solo approximate agreement in asynchronous wait-free message-passing systems.

These results establish for the first time a hierarchy of wait-free models that, while weaker than the basic read/write model, are nevertheless strong enough to solve non-trivial tasks.


Convex Hull Iterate Model Barycentric Subdivision Approximate Agreement Communication Object 
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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© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Maurice Herlihy
    • 1
  • Sergio Rajsbaum
    • 2
  • Michel Raynal
    • 3
    • 4
  • Julien Stainer
    • 4
  1. 1.Brown UniversityProvidenceUSA
  2. 2.Instituto de MathematicasUNAMMexico
  3. 3.Institut Universitaire de FranceFrance
  4. 4.INRIAIRISA Université de Rennes 1Rennes CedexFrance

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