A New Variable Ordering for In-processing Bounded Variable Elimination in SAT Solvers

A New Variable Ordering for In-processing Bounded Variable Elimination in SAT Solvers

Shuolin Li, Chu-Min Li, Mao Luo, Jordi Coll, Djamal Habet, Felip ManyĆ 

Proceedings of the Thirty-Second International Joint Conference on Artificial Intelligence
Main Track. Pages 1979-1987. https://doi.org/10.24963/ijcai.2023/220

Bounded Variable Elimination (BVE) is an important Boolean formula simplification technique in which the variable ordering is crucial. We define a new variable ordering based on variable activity, called ESA (variable Elimination Scheduled by Activity), for in-processing BVE in Conflict-Driven Clause Learning (CDCL) SAT solvers, and incorporate it into several state-of-the-art CDCL SAT solvers. Experimental results show that the new ESA ordering consistently makes these solvers solve more instances on the benchmark set including all the 5675 instances used in the Crafted, Application and Main tracks of all SAT Competitions up to 2022. In particular, one of these solvers with ESA, Kissat_MAB_ESA, won the Anniversary track of the SAT Competition 2022. The behaviour of ESA and the reason of its effectiveness are also analyzed.
Keywords:
Constraint Satisfaction and Optimization: CSO: Satisfiabilty
Constraint Satisfaction and Optimization: CSO: Solvers and tools