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CP
2008
Springer

A Soft Constraint of Equality: Complexity and Approximability

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A Soft Constraint of Equality: Complexity and Approximability
We introduce the SoftAllEqual global constraint, which maximizes the number of equalities holding between pairs of assignments to a set of variables. We study the computational complexity of propagating this constraint, showing that it is intractable in general, since maximizing the number of pairs of equally assigned variables in a set is NP-hard. We propose three ways of coping with NP-hardness. Firstly, we develop a greedy linear-time algorithm to approximate the maximum number of equalities within a factor of 2. Secondly, we identify a tractable (polynomial) class for this constraint. Thirdly, we identify a parameter based on this class and show that the SoftAllEqual constraint is fixedparameter tractable with respect to this parameter.
Emmanuel Hebrard, Barry O'Sullivan, Igor Razgon
Added 18 Oct 2010
Updated 18 Oct 2010
Type Conference
Year 2008
Where CP
Authors Emmanuel Hebrard, Barry O'Sullivan, Igor Razgon
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