Distributed maximal matching: greedy is optimal

  • Authors:
  • Juho Hirvonen;Jukka Suomela

  • Affiliations:
  • University of Helsinki, Helsinki, Finland;University of Helsinki, Helsinki, Finland

  • Venue:
  • PODC '12 Proceedings of the 2012 ACM symposium on Principles of distributed computing
  • Year:
  • 2012

Quantified Score

Hi-index 0.00

Visualization

Abstract

We study distributed algorithms that find a maximal matching in an anonymous, edge-coloured graph. If the edges are properly coloured with k colours, there is a trivial greedy algorithm that finds a maximal matching in k-1 synchronous communication rounds. The present work shows that the greedy algorithm is optimal in the general case: if A is a deterministic distributed algorithm that finds a maximal matching in anonymous, k-edge-coloured graphs, then there is a worst-case input in which the running time of A is at least k1 rounds. If we focus on graphs of maximum degree Δ, it is known that a maximal matching can be found in O(Δ+ log* k) rounds, and prior work implies a lower bound of Ω(polylog(Δ) + log* k) rounds. Our work closes the gap between upper and lower bounds: the complexity is Θ(Δ+ log* k) rounds. To our knowledge, this is the first linear-in-Δ lower bound for the distributed complexity of a classical graph problem.