DMCA
Generating Special-purpose Stateless Propagators for Arbitrary Constraints
Cached
Download Links
| Citations: | 3 - 1 self |
BibTeX
@MISC{Gent_generatingspecial-purpose,
author = {Ian P. Gent and Chris Jefferson and Ian Miguel and Peter Nightingale},
title = {Generating Special-purpose Stateless Propagators for Arbitrary Constraints},
year = {}
}
Share
 |
 |
 |
 |
||
OpenURL
Abstract
Abstract. Given an arbitrary constraint c on n variables with domain size d, we show how to generate a custom propagator that establishes GAC in time O(nd) by precomputing the propagation that would be performed on every reachable subdomain of scope(c). Our propagators are stateless: they store no state between calls, and so incur no overhead in storing and backtracking state during search. The preprocessing step can take exponential time and the custom propagator is potentially exponential in size. However, for small constraints used repeatedly, in one problem or many, this technique can provide substantial practical gains. Our experimental results show that, compared with optimised implementations of the table constraint, this technique can lead to an order of magnitude speedup, while doing identical search on realistic problems. The technique can also be many times faster than a decomposition into primitive constraints in the Minion solver. Propagation is so fast that, for constraints available in our solver, the generated propagator compares well with a human-optimised propagator for the same constraint. 1
Keyphrases
arbitrary constraint special-purpose stateless propagator custom propagator primitive constraint preprocessing step domain size magnitude speedup generated propagator human-optimised propagator exponential time minion solver identical search realistic problem many time table constraint reachable subdomain optimised implementation experimental result substantial practical gain small constraint
