Satisfiability decay along conjunctions of pseudo-random clauses

Eli Shamir*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

k-SAT is a fundamental constraint satisfaction problem. It involves S(m), the satisfaction set of the conjunction of m clauses, each clause a disjunction of k literals. The problem has many theoretical, algorithmic and practical aspects. When the clauses are chosen at random it is anticipated (but not fully proven) that, as the density parameter m/n (n the number of variables) grows, the transition of S(m) to being empty, is abrupt: It has a "sharp threshold", with probability 1 - o(1). In this articlewe replace the random ensemble analysis by a pseudo-random one: Derive the decay rule for individual sequences of clauses, subject to combinatorial conditions, which in turn hold with probability 1 - o(1). This is carried out under the big relaxation that k is not constant but k = γ log n, or even r log log n. Then the decay of S is slow, "near-perfect" (like a radioactive decay), which entails sharp thresholds for the transition-time of S below any given level, down to S = 0.

Original languageEnglish
Pages (from-to)815-825
Number of pages11
JournalLogic Journal of the IGPL
Volume14
Issue number5
DOIs
StatePublished - Oct 2006

Keywords

  • Constraint satisfaction
  • k-SAT
  • Learning from examples
  • Pseudorandom analysis
  • Sharp thresholds
  • Unique k-SAT representations

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