Boosting local search thanks to {CDCL}

International audienceIn this paper, a novel hybrid and complete approach for propositional satisfiability, called SAT HYS (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

Une recherche locale dirigée par l'analyse de conflits pour la satisfiabilité

National audienceCet article présente un algorithme de recherche locale guidée par l'analyse de conflits pour résoudre le problème SAT. L'usage d'une telle analyse, permettrait d'exploiter les dépendances entre les variables particulièrement présentes dans des instances structurées et d'accroître l'effet de la propagation unitaire. Les premiers résultats expérimentaux sont prometteurs

Hybrid solvers for the Boolean Satisfiability problem: an exploration

The Boolean Satisfiability problem (SAT) is one of the most extensively researched NP-complete problems in Computer Science. This thesis focuses on the design of feasible solvers for this problem. A SAT problem instance is a formula in propositional logic. A SAT solver attempts to find a solution for the formula. Our research focuses on a newer solver paradigm, hybrid solvers, where two solvers are combined in order to gain the benefits from both solvers in the search for a solution. Our hybrid solver, AmbSAT, combines two well-known solvers: the systematic Davis-Putnam-Logemann-Loveland solver (DPLL) and the stochastic WalkSAT solver. AmbSAT\u27s design is original and differs from the hybrid solver designs in the research literature. AmbSAT utilizes a DPLL algorithm to lead the search and WalkSAT at appropriate points to aid in the search process. Central to AmbSAT\u27s design is the notion of ambivalence. Essentially, ambivalence attempts to formally identify the points in time when the DPLL solver might be well served by further guidance from WalkSAT. In this thesis, we present three different ambivalence notions and analyze their performance against a pure DPLL solver. Our results are promising, and indicate that AmbSAT performs better than a pure DPLL solver on a diverse collection of SAT problem instances