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A sharp threshold in proof complexity yields lower bounds for satisfiability search

机译:证明复杂性的严格阈值会产生可满足性搜索的下限

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摘要

Let F(rhon, Deltan) denote a random CNF formula consisting of rhon randomly chosen 2-clauses and Deltan randomly chosen 3-clauses, for some arbitrary constants rho, Delta greater than or equal to 0. It is well-known that, with probability 1 - o(1), if rho > 1 then F(rhon, Deltan) has a linear-size resolution refutation. We prove that, with probability 1- o(1), if rho < 1 then F(rhon, Deltan) has no subexponential-size resolution refutation. Our result also yields the first proof that random 3-CNF formulas with densities well below the generally accepted range of the satisfiability threshold (and thus believed to be satisfiable) cause natural Davis-Putnam algorithms to take exponential time (to find a satisfying assignment). (C) 2003 Published by Elsevier Inc. [References: 36]
机译:令F(rhon,Deltan)表示一个随机CNF公式,该公式由rhon随机选择的2个子句和Deltan随机选择的3个子句组成,对于某些任意常数rho,Delta大于或等于0。概率为1-o(1),如果rho> 1,则F(rhon,Deltan)具有线性大小的分辨率反驳。我们证明,当概率为1 o(1)时,如果rho <1,则F(rhon,Deltan)没有次指数大小的分辨率反驳。我们的结果还提供了第一个证明,即密度远低于可满足性阈值的公认范围(因此被认为是可满足的)的随机3-CNF公式导致自然的Davis-Putnam算法花费指数时间(以找到令人满意的赋值) 。 (C)2003年由Elsevier Inc.出版。[参考:36]

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