A Threshold for a Polynomial Solution of #2SAT

  • Authors:
  • Guillermo De Ita;J. Raymundo Marcial-Romero;José Antonio Hernández

  • Affiliations:
  • (Correspd.) Computer Sciences Department, Benemérita Universidad Autónoma de Puebla, México. deita@cs.buap.mx;Facultad de Ingeniería, Universidad Autónoma del Estado de México. rmarcial@fi.uaemex.mx;Facultad de Ingeniería, Universidad Autónoma del Estado de México. xoseahernandez@gmail.com

  • Venue:
  • Fundamenta Informaticae - Latin American Workshop on Logic Languages, Algorithms and New Methods of Reasoning (LANMR)
  • Year:
  • 2011

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Abstract

The #SAT problem is a classical #P-complete problem even for monotone, Horn and two conjunctive formulas (the last known as #2SAT). We present a novel branch and bound algorithm to solve the #2SAT problem exactly. Our procedure establishes a new threshold where #2SAT can be computed in polynomial time. We show that for any 2-CF formula F with n variables where #2SAT(F) ≤ p(n), for some polynomial p, #2SAT(F) is computed in polynomial time. This is a new way to measure the degree of difficulty for solving #2SAT and, according to such measure our algorithm allows to determine a boundary between ‘hard’ and ‘easy’ instances of the #2SAT problem.