Predicting Derivation Lengths in Rule-based Constraint Programs
نویسنده
چکیده
We automatically predict the maximal number of rule applications, i.e. worst-case derivation lengths of computations, in rule-based constraint solver programs written in the CHR language. The derivation lengths are derived from rankings used in termination proofs for the respective programs. We are especially interested in rankings that give us a good upper bound, we call such rankings tight. We apply our method to constraint solvers ranging from Boolean and arithmetic to terminological and path-consistent constraints. In most cases, the worst-case derivation length is linear in the syntactic size of the constraint problem. RÉSUMÉ. Nous prévoyons automatiquement le nombre maximal d’application de règles (c.-à.d. longueur de dérivation dans les pires des cas) dans des solveur de contraintes basés sur des règles écrits dans le langage CHR. Les longueurs de dérivation sont dérivées à partir des rangs utilisés dans des preuves de terminaison pour ces programmes. Nous sommes particulièrement intéressés par les rangs qui nous donnent une bonne limite supérieure. Nous appliquons notre méthode sur des differents solveurs de contraintes, tels que contraintes booléennes, équations linéaires et contraintes terminologiques. Dans la plupart des cas, la longueur de dérivation (dans les pires des cas) est linéaire dans la taille syntactique du problème.
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