Hard examples for resolution

  • Authors:
  • Alasdair Urquhart

  • Affiliations:
  • Univ. of Toronto, Toronto, Ont., Canada

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1987

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Abstract

Exponential lower bounds are proved for the length-of-resolution refutations of sets of disjunctions constructed from expander graphs, using the method of Tseitin. Since these sets of clauses encode biconditionals, they have short (polynomial-length) refutations in a standard axiomatic formulation of propositional calculus.