Boosting Local Search Thanks to cdcl

Abstract

Abstract. In this paper, a novel hybrid and complete approach for propositional satisfiability, called SATHYS (Sat Hybrid Solver), is introduced. It efficiently combines the strength of both local search and CDCL based SAT solvers. Considering the consistent partial assignment under construction by the CDCL SAT solver, local search is used to extend it to a model of the Boolean formula, while the CDCL component is used by the local search one as a strategy to escape from a local minimum. Additionally, both solvers heavily cooperate thanks to relevant information gathered during search. Experimentations on SAT instances taken from the last competitions demonstrate the efficiency and the robustness of our hybrid solver with respect to the state-of-the-art CDCL based, local search and hybrid SAT solvers.

Local Search Based on Conflict Analysis for the Satisfiability Problem

“…At each occurrence of this case, a conflict graph and a partial assignment is derived from beginning followed by some flips and clause learning. In [8], Sathys is defined as an hybridization method between a LS and a minisat-like solvers working alternately according to some balancing criteria which indicates the evolution of the search. In [9], a comparable hybridization scheme to Sathys is proposed with a memory sharing in a parallel architecture for Max-SAT problem.…”

“…This restriction is motivated by the fact that the assignments of I p variables is done thanks to hypothetical relations that should be maintained. A comparative process is also used in [8], [9] for other reasons.…”

Stochastic Local Search for SMT: Combining Theory Solvers with WalkSAT

“…A few attempts have been made in order to enhance SLS algorithms with techniques borrowed from CDCL solvers (e.g. [6,4]). In particular, Belov and Stachniak [6] propose two techniques that exploit the search history to improve the variable selection process of the classic SLS procedures for SAT.…”

Inference Rules in Local Search for Max-SAT

“…One of the difficulties to overcome in order to make this rule applicable in a LS algorithm is the definition of refutation trees in the LS context. This issue has already been studied for the SAT context, for example in [19], [20], [21], [22], [23]. Moreover, a balance must be struck between the time spent on applying the rule and the time consumed in solving the instance.…”