Hiding Satisfying Assignments: Two Are Better than One

The evaluation of incomplete satisfiability solvers depends critically on the availability of hard satisfiable instances. A plausible source of such instances consists of random kSAT formulas whose clauses are chosen uniformly from among all clauses satisfying some randomly chosen truth assignment A. Unfortunately, instances generated in this manner tend to be relatively easy and can be solved efficiently by practical heuristics. Roughly speaking, for a number of different algorithms, A acts as a stronger and stronger attractor as the formula's density increases. Motivated by recent results on the geometry of the space of satisfying truth assignments of random k-SAT and NAE-k-SAT formulas, we introduce a simple twist on this basic model, which appears to dramatically increase its hardness. Namely, in addition to forbidding the clauses violated by the hidden assignment A, we also forbid the clauses violated by its complement, so that both A and A are satisfying. It appears that un...

• Type: Conference
• Year: 2004
• Where: AAAI
• Authors: Dimitris Achlioptas, Haixia Jia, Cristopher Moore
• Keywords: AAAI 2004, Hard Satisfiable Instances, Incomplete Satisfiability Solvers, Intelligent Agents, Truth Assignment