Extending Dual Arc Consistency

Comparisons between primal and dual approaches have re-cently been extensively studied and evaluated from a theoret-ical standpoint based on the amount of pruning achieved by each of these when applied to non-binary constraint satisfac-tion problems. Enforcing arc consistency on the dual encod-ing has been shown to strictly dominate enforcing GAC on the primal encoding (Stergiou & Walsh 1999). More recently, extensions to dual arc consistency have extended these results to dual encodings that are based on the construction of com-pact constraint coverings, that retain the completeness of the encodings, while using a fraction of the space. In this paper we present a complete theoretical evaluation of these different consistency techniques and also demonstrate how arbitrarily high levels of consistency can be achieved efficiently using them