Coloration neighbourhood search with forward checking

Two contrasting search paradigms for solving combinatorial problems are systematic backtracking and local search. The former is often effective on highly structured problems because of its ability to exploit consistency techniques, while the latter tends to scale better on very large problems. Neither approach is ideal for all problems, and a current trend in artificial intelligence is the hybridisation of search techniques. This paper describes a use of forward checking in local search: pruning coloration neighbourhoods for graph colouring. The approach is evaluated on standard benchmarks and compared with several other algorithms. Good results are obtained; in particular, one variant finds improved colourings on geometric graphs, while another is very effective on equipartite graphs. Its application to other combinatorial problems is discussed.