Constraint Propagation in Graph Coloring
Journal of Heuristics
Searching for doubly self-orthogonal latin squares
CP'11 Proceedings of the 17th international conference on Principles and practice of constraint programming
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For the Queens_n2 graph coloring problems no chromatic numbers are available for n 9 except where n is not a multiple of 2 or 3. In this paper we propose an exact algorithm that takes advantage of the particular structure of these graphs. The algorithm works on the independent sets of the graph rather than on the vertices to be colored. It combines branch and bound, for independent set assignment, with a clique based filtering procedure. A first experimentation of this approach provided the coloring number values ranging for n = 10 to n = 14.