Decomposition of the NVALUE constraint
Abstract
We study decompositions of the global NVALUE constraint. Our main contribution is theoretical: we show that there are propagators for global constraints like NVALUE which decomposition can simulate with the same time complexity but with a much greater space complexity. This suggests that the benefit of a global propagator may often not be in saving time but in saving space. Our other theoretical contribution is to show for the first time that range consistency can be enforced on NVALUE with the same worst-case time complexity as bound consistency. Finally, the decompositions we study are readily encoded as linear inequalities. We are therefore able to use them in integer linear programs.
Cite
@article{arxiv.1007.0603,
title = {Decomposition of the NVALUE constraint},
author = {Christian Bessiere and George Katsirelos and Nina Narodytska and Claude-Guy Quimper and Toby Walsh},
journal= {arXiv preprint arXiv:1007.0603},
year = {2010}
}
Comments
To appear in the Proceedings of the 16th International Conference on Principles and Practice of Constraint Programming 2010 (CP 2010). An earlier version appeared in the Proceedings of the Eighth International Workshop on Constraint Modelling and Reformulation, held alongside the 15th International Conference on Principles and Practice of Constraint Programming (CP 2009)