Convergence Speed in Distributed Consensus and Averaging

  • Authors:
  • Alex Olshevsky;John N. Tsitsiklis

  • Affiliations:
  • alex_o@mit.edu and jnt@mit.edu;-

  • Venue:
  • SIAM Journal on Control and Optimization
  • Year:
  • 2009

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Abstract

We study the convergence speed of distributed iterative algorithms for the consensus and averaging problems, with emphasis on the latter. We first consider the case of a fixed communication topology. We show that a simple adaptation of a consensus algorithm leads to an averaging algorithm. We prove lower bounds on the worst-case convergence time for various classes of linear, time-invariant, distributed consensus methods, and provide an algorithm that essentially matches those lower bounds. We then consider the case of a time-varying topology, and provide a polynomial-time averaging algorithm.