Improved approximations of independent sets in bounded-degree graphs via subgraph removal

  • Authors:
  • Magnús M. Halldórsson;Jaikumar Radhakrishnan

  • Affiliations:
  • School of Information Science, Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa 923-12, Japan;Theoretical Computer Science Group, Tata Institute of Fundamental Research, Bombay, India

  • Venue:
  • Nordic Journal of Computing
  • Year:
  • 1994

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Abstract

Finding maximum independent sets in graphs with bounded maximum degree Δ is a well-studied NP-complete problem. We introduce an algorithm schema for improving the approximation of algorithms for this problem, which is based on preprocessing the input by removing cliques.We give an implementation of a theorem on the independence number of clique-free graphs, and use it to obtain an O(Δ/log log Δ) performance ratio with our schema. This is the first o(Δ) ratio for the independent set problem. We also obtain an efficient method with a Δ/6(1 + o(1)) performance ratio, improving on the best performance ratio known for intermediate values of Δ.