A best - rst - search approach to constraint satisfaction problems ∗

Backtrack-style exhaustive search algorithms for NP-hard problems, such as constraint satisfaction, tend to have large variance in their runtime. This is because fortunate branching decisions can lead to nding a solution quickly, whereas unfortunate decisions in another run can lead the algorithm to a region of the search space with no solutions. In this paper, we show how a bestrst-search heuristic can be used to mitigate this problem and signi cantly speed up the algorithm, without sacri cing the optimality of the output.