Satisfiability threshold of the skewed random k-SAT

  • Authors:
  • Danila A. Sinopalnikov

  • Affiliations:
  • Department of Mathematics and Mechanics, St. Petersburg State University, Russia

  • Venue:
  • SAT'04 Proceedings of the 7th international conference on Theory and Applications of Satisfiability Testing
  • Year:
  • 2004

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Abstract

We consider the k-satisfiability problem. It is known that the random k-SAT model, in which the instance is a set of mk-clauses selected uniformly from the set of all k-clauses over n variables, has a phase transition at a certain clause density, below which most instances are satisfiable and above which most instances are unsatisfiable. The essential feature of the random k-SAT is that positive and negative literals occur with equal probability in a random formula. How does the phase transition behavior change as the relative probability of positive and negative literals changes? In this paper we focus on a distribution in which positive and negative literals occur with different probability. We present empirical evidence for the satisfiability phase transition for this distribution. We also prove an upper bound on the satisfiability threshold and a linear lower bound on the number of literals in satisfying partial assignments of skewed random k-SAT formulas.