Guiding Backtrack Search by Tracking Variables During Constraint Propagation
Résumé
It is well-known that variable ordering heuristics play a central role in solving efficiently Constraint Satisfaction Problem (CSP) instances. From the early 80’s, and during more than two decades, the dynamic variable ordering heuristic selecting the variable with the smallest domain was clearly prevailing. Then, from the mid 2000’s, some adaptive heuristics have been introduced: their principle is to collect some useful information during the search process in order to take better informed decisions. Among those adaptive heuristics, wdeg/dom (and its variants) remains particularly robust. In this paper, we introduce an original heuristic based on the midway processing of failing executions of constraint propagation: this heuristic called pick/dom tracks the variables that are directly involved in the process of constraint propagation, when ending with a conflict. The robustness of this new heuristic is demonstrated from a large experimentation conducted with the constraint solver ACE. Interestingly enough, one can observe some complementary between the early, midway and late forms of processing of conflicts.
Mots clés
Variable Ordering Heuristics
Variable Weighting
Computing methodologies → Discrete space search
2012 ACM Subject Classification Computing methodologies → Discrete space search phrases Variable Ordering Heuristics
Variable Weighting Digital Object Identifier 10 4230/LIPIcs CP 2023 9
Variable Weighting Digital Object Identifier 10
4230/LIPIcs
CP
2023
9
Domaines
Informatique [cs]
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