an:06323002
Zbl 1366.68072
Bergman, David; Cire, Andre A.; van Hoeve, Willem-Jan
MDD propagation for sequence constraints
EN
J. Artif. Intell. Res. (JAIR) 50, 697-722 (2014).
00332785
2014
j
68Q17 68Q25 68T20
Summary: We study propagation for the \textsc{Sequence} constraint in the context of constraint programming based on limited-width MDDs. Our first contribution is proving that establishing MDD-consistency for \textsc{Sequence} is NP-hard. Yet, we also show that this task is fixed parameter tractable with respect to the length of the sub-sequences. In addition, we propose a partial filtering algorithm that relies on a specific decomposition of the constraint and a novel extension of MDD filtering to node domains. We experimentally evaluate the performance of our proposed filtering algorithm, and demonstrate that the strength of the MDD propagation increases as the maximum width is increased. In particular, MDD propagation can outperform conventional domain propagation for \textsc{Sequence} by reducing the search tree size and solving time by several orders of magnitude. Similar improvements are observed with respect to the current best MDD approach that applies the decomposition of \textsc{Sequence} into \textsc{Among} constraints.