Space bounds for resolution

  • Authors:
  • Juan Luis Esteban;Jacobo Torán

  • Affiliations:
  • Dept. Llenguatges i sistemes informàtics, Universitat Politècnica de Catalunya, Barcelona, Spain;Abt. Teoretische Informatik, Universität Ulm, Ulm, Germany

  • Venue:
  • STACS'99 Proceedings of the 16th annual conference on Theoretical aspects of computer science
  • Year:
  • 1999

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Abstract

We introduce a new way to measure the space needed in a resolution refutation of a CNF formula in propositional logic. With the former definition [6] the space required for the resolution of any unsatisfiable formula in CNF is linear in the number of clauses. The new definition allows a much finer analysis of the space in the refutation, ranging from constant to linear space. Moreover, the new definition allows to relate the space needed in a resolution proof of a formula to other well studied complexity measures. It coincides with the complexity of a pebble game in the resolution graphs of a formula, and as we show, has strong relationships to the size of the refutation. We also give upper and lower bounds on the space needed for the resolution of unsatisfiable formulas.