NP-hard and linear variants of hypergraph partitioning

  • Authors:
  • Laurent Lyaudet

  • Affiliations:
  • LIP (UMR CNRS, ENS Lyon, INRIA, Univ. Claude Bernard Lyon 1), École Normale Supérieure de Lyon, 46 allée dItalie 69364 LYON cedex 07, France

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2010

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Abstract

This article presents an infinite family of combinatorial problems that shows abrupt changes of complexity between neighbour problems. We define problem P"k^l as a purely constraint-driven variant of hypergraph partitioning with parameters k and l as follows. Given a hypergraph on n vertices and k sizes of colours t"1,...,t"k of sum n, can we colour the vertices with k colours of given size such that each hyperedge intersects at most l colours? We show that, for fixed parameters k and l, P"k^l is: polynomial when l=1, and NP-complete when l1 on the class of hypergraphs; NP-complete when l=1, and linear when l1 on the class of hypergraphs with pairwise disjoint hyperedges. This inversion of complexity is possible since hypergraphs with disjoint hyperedges can be encoded in a more compact way, namely @Q(mlog(n)) instead of @Q(mn) bits (n and m are the number of vertices and edges of the hypergraph).