| | |
Summary: Look-Ahead Versus Look-Back for Satis ability
Problems
Chu Min Li and Anbulagan
LaRIA, Universite de Picardie Jules Verne
33, Rue St. Leu, 80039 Amiens Cedex 01, France
tel: (33) 3 22 82 78 75, fax: (33) 3 22 82 75 02
e-mail: fcli@laria.u-picardie.fr, Anbulagan@utc.frg
Abstract. CNF propositional satis ability (SAT) is a special kind of
the more general Constraint Satisfaction Problem (CSP). While look-
back 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 struc-
|
