On Spatial Gossip Algorithms for Average Consensus

  • Authors:
  • Michael G. Rabbat

  • Affiliations:
  • Dept. of Electrical and Computer Engineering, McGill University, Montréal, Québec. Email: michael.rabbat@mcgill.ca

  • Venue:
  • SSP '07 Proceedings of the 2007 IEEE/SP 14th Workshop on Statistical Signal Processing
  • Year:
  • 2007

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Abstract

This paper investigates the use of spatial gossip to compute the average consensus in networks such as grids or random geometric graphs, where connectivity is a function of proximity. Randomized gossip is a framework for distributed computation where, at each iteration, a random pair of nodes exchanges information, and then updates their local values by averaging. This simple protocol converges to an average consensus: every node obtains the average of the initial values across the network. In spatial gossip, if the distance between two nodes is d, then they communicate with probability proportional to d-β for some β ≥ 0. The special case β = 0 corresponds to an algorithm known in the sensor network literature as geographic gossip. Dimakis et al. have shown that geographic gossip computes the average to accuracy n-1 in O(n3/2√log n) transmissions. In this paper we show that the same rates are achieved for β = 2 and β = 3. Each setting offers a different balance between the rate of convergence (in gossip rounds) and the average number of transmissions per gossip round. We illustrate, via simulation, that spatial gossip with β = 2 generally yields superior performance over geographic gossip by a constant factor.