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arXiv · 1104.4279

Satisfiability of Acyclic and Almost Acyclic CNF Formulas

Sebastian Ordyniak·Daniel Paulusma·Stefan Szeider
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Abstract

We show that the Satisfiability (SAT) problem for CNF formulas with β-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 β-acyclic formulas and this superclass with a number of known polynomial formula classes. We then study the parameterized complexity of SAT for "almost" β-acyclic instances, using as parameter the formula's distance from being β-acyclic. As distance we use the size of a smallest strong backdoor set and the β-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.

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Sebastian Ordyniak, Daniel Paulusma, Stefan Szeider. 2013-04-03. Satisfiability of Acyclic and Almost Acyclic CNF Formulas. https://doi.org/10.1016/j.tcs.2012.12.039

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