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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