A local algorithm for finding dense subgraphs

  • Authors:
  • Reid Andersen

  • Affiliations:
  • Microsoft Research

  • Venue:
  • Proceedings of the nineteenth annual ACM-SIAM symposium on Discrete algorithms
  • Year:
  • 2008

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Abstract

A local graph algorithm is one that searches for an approximation of the best solution near a specified starting vertex, and has a running time independent of the size of the graph. Recently, local algorithms have been developed for graph partitioning and clustering. In this paper, we present a local algorithm for finding dense subgraphs of bipartite graphs, according to the measure of density proposed by Kannan and Vinay. The algorithm takes as input a bipartite graph with a specified starting vertex, and attempts to find a dense subgraph near that vertex. We prove the following local approximation guarantee for the algorithm. For any subgraph S with k vertices and density θ, there is a large set of starting vertices within S for which the algorithm produces a subgraph with density Ω(θ/log Δ), where Δ is the maximum degree. The running time of the algorithm is O(Δk2), independent of the number of vertices in the graph.