Using Local Search to Speed Up Filtering Algorithms for Some NP-Hard Constraints

Abstract. This paper proposes to use local search inside filtering algo-rithms of combinatorial structures for which achieving a desired level of consistency is too computationally expensive. Local search quickly pro-vides supports for many variable-value pairs, thus reducing the effort re-quired to check and potentially filter the rest of them. The idea is demon-strated on the SomeDifferent constraint, a graph coloring substructure. An experimental evaluation confirms its significant computational gain in many cases.