Untangling Partial Agreement: Iterated x-consensus Simulations

  • Damien Imbs
  • Sergio Rajsbaum
  • Adrián Valle
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 9212)


The basic read/write shared memory model where asynchronous and crash prone processes communicate to solve a task is difficult to analyze. A more structured model is the iterated immediate snapshot model (IIS), where processes execute communication closed rounds. In each round, they communicate using read/write registers that cannot be reused in later rounds. It is known that a task is solvable in the IIS model if and only if it is solvable in the basic read/write model. Both models are also equivalent when, in addition to read/write registers, processes also have access to stronger communication objects called 01-tasks.

This paper extends further the task computability equivalence presenting a simulation that includes x-consensus objects, which solve consensus among up to x processes. The simulation implies that an iterated model where processes communicate through a sequence consisting only of x-consensus objects is equivalent to the basic shared memory model augmented with x-consensus objects.


Asynchronous systems Consensus Distributed computing Iterated Immediate Snapshot Read/write shared memory Task solvability Wait-freedom 


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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  1. 1.Department of MathematicsUniversity of BremenBremenGermany
  2. 2.Instituto de MatemáticasUNAMCiudad de MexicoMexico
  3. 3.OracleZapopanMexico

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