Look-ahead versus look-back for satisfiability problems

  • Chu Min Li
  • Anbulagan
Session 5b
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1330)


CNF propositional satisfiability (SAT) is a special kind of the more general Constraint Satisfaction Problem (CSP). While lookback techniques appear to be of little use to solve hard random SAT problems, it is supposed that they are necessary to solve hard structured SAT problems. In this paper, we propose a very simple DPL procedure called Satz which only employs some look-ahead techniques: a variable ordering heuristic, a forward consistency checking (Unit Propagation) and a limited resolution before the search, where the heuristic is itself based on unit propagation. Satz is favorably compared on random 3-SAT problems with three DPL procedures among the best in the literature for these problems. Furthermore on a great number of problems in 4 well known SAT benchmarks Satz reaches or outspeeds the performance of three other DPL procedures among the best in the literature for structured SAT problems. The comparative results suggest that a suitable exploitation of look-ahead techniques, while very simple and efficient for random SAT problems, may allow to do without sophisticated look-back techniques in a DPL procedure.


Search Tree Unit Propagation Conjunctive Normal Form Unit Clause Conjunctive Normal Form Formula 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Chu Min Li
    • 1
  • Anbulagan
    • 1
  1. 1.LaRIA, Université de Picardie Jules VerneAmiens Cédex 01France

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