On finding short resolution refutations and small unsatisfiable subsets

  • Authors:
  • Michael R. Fellows;Stefan Szeider;Graham Wrightson

  • Affiliations:
  • School of Electrical Engineering and Computer Science, University of Newcastle, Callaghan, NSW, Australia;Department of Computer Science, Durham University, Durham, UK;School of Electrical Engineering and Computer Science, University of Newcastle, Callaghan, NSW, Australia

  • Venue:
  • Theoretical Computer Science - Parameterized and exact computation
  • Year:
  • 2006

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Abstract

We consider the parameterized problems of whether a given set of clauses can be refuted within k resolution steps, and whether a given set of clauses contains an unsatisfiable subset of size at most k. We show that both problems are complete for the class W[1], the first level of the W-hierarchy of fixed-parameter intractable problems. Our results remain true if restricted to 3-SAT instances and/or to various restricted versions of resolution including tree-like resolution, input resolution, and read-once resolution. Applying a metatheorem of Frick and Grohe, we show that, restricted to classes of sets of clauses of locally bounded treewidth, the considered problems are fixed-parameter tractable. For example, the problems are fixed-parameter tractable for planar CNF formulas.