Parameterized Bounded-Depth Frege Is not Optimal

  • Authors:
  • Olaf Beyersdorff;Nicola Galesi;Massimo Lauria;Alexander A. Razborov

  • Affiliations:
  • University of Leeds;Sapienza University Rome;Sapienza University Rome;University of Chicago

  • Venue:
  • ACM Transactions on Computation Theory (TOCT)
  • Year:
  • 2012

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Abstract

A general framework for parameterized proof complexity was introduced by Dantchev et al. [2007]. There, the authors show important results on tree-like Parameterized Resolution---a parameterized version of classical Resolution---and their gap complexity theorem implies lower bounds for that system. The main result of this article significantly improves upon this by showing optimal lower bounds for a parameterized version of bounded-depth Frege. More precisely, we prove that the pigeonhole principle requires proofs of size nΩ(k) in parameterized bounded-depth Frege, and, as a special case, in dag-like Parameterized Resolution. This answers an open question posed in Dantchev et al. [2007]. In the opposite direction, we interpret a well-known technique for FPT algorithms as a DPLL procedure for Parameterized Resolution. Its generalization leads to a proof search algorithm for Parameterized Resolution that in particular shows that tree-like Parameterized Resolution allows short refutations of all parameterized contradictions given as bounded-width CNFs.