Abstract
A resolution proof of an unsatisfiable propositional formula in conjunctive normal form is a “Davis-Putnam resolution proof” iff there exists a sequence of the variables of the formula such thatx is eliminated (with the resolution rule) beforey on any branch of the proof tree representing the resolution proof, only ifx is beforey in this sequence. Davis-Putnam resolution is one of several resolution restrictions. It is complete.
We present an infinite family of unsatisfiable propositional formulas and show: These formulas have unrestricted resolution proofs whose length is polynomial in their size. All Davis-Putnam resolution proofs of these formulas are of superpolynomial length. In the terminology of [4, definition 1.5]: Davis-Putnam resolution does notp-simulate unrestricted resolution.
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Goerdt, A. Davis-Putnam resolution versus unrestricted resolution. Ann Math Artif Intell 6, 169–184 (1992). https://doi.org/10.1007/BF01531027
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DOI: https://doi.org/10.1007/BF01531027