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arXiv 1102.2880cs.CC
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四个元素的最小CSP:超越子模块化

Min CSP on Four Elements: Moving Beyond Submodularity

Peter Jonsson, Fredrik Kuivinen, Johan Thapper

摘要:

我们报告的价值约束满足问题(VCSP)的复杂性的新结果。在唯一对策猜想下,有限值VCSP的可逼近性已经得到了很好的理解。然而,目前还没有一个可以在多项式时间内精确求解的VCSP特性。这是不令人满意的,因为这样的结果是有趣的组合优化的角度来看,有深刻的联系,例如,submodular和bisubmodular最小化。我们考虑最小和最大CSP问题(即成本函数仅在{0,1}中获得值)在四元素域上,并确定所有易处理的片段。类似的分类以前已知的两个和三个元素域。在这个过程中,我们引入了一类新的听话的VCSPs的基础上推广的子模块。我们还扩展和修改了Kolmogorov和Zivny(最初由Takhanov介绍)的基于图形的技术,以有效地获得硬度结果。这使我们能够证明结果,而无需依赖计算机辅助的案例分析(在研究VCSP的复杂性和可近似性时,这是相当常见的)。通过引入强大的还原技术,硬度结果进一步简化。

英文摘要:

We report new results on the complexity of the valued constraint satisfaction problem (VCSP). Under the unique games conjecture, the approximability of finite-valued VCSP is fairly well-understood. However, there is yet no characterisation of VCSPs that can be solved exactly in polynomial time. This is unsatisfactory, since such results are interesting from a combinatorial optimisation perspective; there are deep connections with, for instance, submodular and bisubmodular minimisation. We consider the Min and Max CSP problems (i.e. where the cost functions only attain values in {0,1}) over four-element domains and identify all tractable fragments. Similar classifications were previously known for two- and three-element domains. In the process, we introduce a new class of tractable VCSPs based on a generalisation of submodularity. We also extend and modify a graph-based technique by Kolmogorov and Zivny (originally introduced by Takhanov) for efficiently obtaining hardness results in our setting. This allow us to prove the result without relying on computer-assisted case analyses (which otherwise are fairly common when studying the complexity and approximability of VCSPs.) The hardness results are further simplified by the introduction of powerful reduction techniques.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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