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arXiv 1504.03543cs.LO
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有限值CSP的可定义性二分法

A Definability Dichotomy for Finite Valued CSPs

Anuj Dawar, Pengming Wang

摘要:

有限值约束满足问题是描述许多自然优化问题的一种形式,其中对变量可以采用的值的约束具有合理的权重,目的是找到最小成本的分配。Thapper和Zivny最近建立了有限值约束语言的复杂性二分法。他们表明,每一个这样的语言要么产生一个多项式时间可解的优化问题,或一个NP难的,并建立一个标准来区分这两种情况。我们细化二分法表明,在第一类中的所有优化问题是可定义的定点语言计数,而在第二类中的所有语言是不可定义的,即使在无限逻辑计数。我们的可定义性二分法不以任何复杂性理论假设为条件。

英文摘要:

Finite valued constraint satisfaction problems are a formalism for describing many natural optimization problems, where constraints on the values that variables can take come with rational weights and the aim is to find an assignment of minimal cost. Thapper and Zivny have recently established a complexity dichotomy for finite valued constraint languages. They show that each such language either gives rise to a polynomial-time solvable optimization problem, or to an NP-hard one, and establish a criterion to distinguish the two cases. We refine the dichotomy by showing that all optimization problems in the first class are definable in fixed-point language with counting, while all languages in the second class are not definable, even in infinitary logic with counting. Our definability dichotomy is not conditional on any complexity-theoretic assumption.

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