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Satisfiability of Acyclic and Almost Acyclic CNF Formulas

By Sebastian Ordyniak, Daniel Paulusma and Stefan Szeider


We show that the Satisfiability (SAT) problem for CNF formulas with {\beta}-acyclic hypergraphs can be solved in polynomial time by using a special type of Davis-Putnam resolution in which each resolvent is a subset of a parent clause. We extend this class to CNF formulas for which this type of Davis-Putnam resolution still applies and show that testing membership in this class is NP-complete. We compare the class of {\beta}-acyclic formulas and this superclass with a number of known polynomial formula classes. We then study the parameterized complexity of SAT for "almost" {\beta}-acyclic instances, using as parameter the formula's distance from being {\beta}-acyclic. As distance we use the size of a smallest strong backdoor set and the {\beta}-hypertree width. As a by-product we obtain the W[1]-hardness of SAT parameterized by the (undirected) clique-width of the incidence graph, which disproves a conjecture by Fischer, Makowsky, and Ravve.Comment: Extended abstracts appeared in the Proceedings of FSTTCS 2010 and SAT 2011. The latter corresponds to revision 1 of this arXiv paper (arXiv:1104.4279v1

Topics: Computer Science - Data Structures and Algorithms
Year: 2013
DOI identifier: 10.1016/j.tcs.2012.12.039
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