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Recognizing frozen variables in constraint satisfaction problems
Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, TCSLAB - Theoretical Computer Science Laboratory.
Departament of Computer Science, University of Durham, Durham, DH1 3LE, United Kingdom.
2004 (English)In: Theoretical Computer Science, ISSN 0304-3975, Vol. 329, no 1-3, 93-113 p.Article in journal (Refereed) Published
Abstract [en]

In constraint satisfaction problems over finite domains, some variables can be frozen, that is, they take the same value in all possible solutions. We study the complexity of the problem of recognizing frozen variables with restricted sets of constraint relations allowed in the instances. We show that the complexity of such problems is determined by certain algebraic properties of these relations. Under the assumption that NP ? coNP (and consequently PTIME ? NP), we characterize all tractable problems, and describe large classes of NP-complete, coNP-complete, and DP-complete problems. As an application of these results, we completely classify the complexity of the problem in two cases: (1) with domain size 2, and (2) when all unary relations are present. We also give a rough classification for domain size 3.© 2004 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
2004. Vol. 329, no 1-3, 93-113 p.
Keyword [en]
Computational complexity, Constraint satisfaction, Frozen variable, Polymorphism
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-45552DOI: 10.1016/j.tcs.2004.08.006OAI: diva2:266448
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2011-01-12

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Jonsson, Peter
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