Solved Forms for Path Ordering Constraints

  • Authors:
  • Robert Nieuwenhuis;José Miguel Rivero

  • Affiliations:
  • -;-

  • Venue:
  • RtA '99 Proceedings of the 10th International Conference on Rewriting Techniques and Applications
  • Year:
  • 1999

Quantified Score

Hi-index 0.00

Visualization

Abstract

A usual technique in symbolic constraint solving is to apply transformation rules until a solved form is reached for which the problem becomes simple. Ordering constraints are well-known to be reducible to (a disjunction of) solved forms, but unfortunately no polynomial algorithm deciding the satisfiability of these solved forms is known. Here we deal with a different notion of solved form, where fundamental properties of orderings like transitivity and monotonicity are taken into account. This leads to a new family of constraint solving algorithms for the full recursive path ordering with status (RPOS), and hence as well for other path orderings like LPO, MPO, KNS and RDO, and for all possible total precedences and signatures. Apart from simplicity and elegance from the theoretical point of view, the main contribution of these algorithms is on efficiency in practice. Since guessing is minimized, and, in particular, no linear orderings between the subterms are guessed, a practical improvement in performance of several orders of magnitude over previous algorithms is obtained, as shown by our experiments.