Boosting Search with Variable Elimination

Abstract. Variable elimination is the basic step of Adaptive Consistency 4 . It transforms the problem into an equivalent one, having one less variable. Unfortunately, there are many classes of problems for which it is infeasible, due to its exponential space and time complexity. However, by restricting variable elimination so that only low arity constraints are processed and recorded, it can be e ectively combined with search, because the elimination of variables, reduces the search tree size. In this paper we introduce VarElimSearchS;k, a hybrid metaalgorithm that combines search and variable elimination. The parameter S names the particular search procedure and k controls the tradeo between the two strategies. The algorithm is space exponential in k. Regarding time, we show that its complexity is bounded by k and a structural parameter from the constraint graph. We also provide experimental evidence that the hybrid algorithm can outperform state-of-the-art algorithms in binary spa...

• Type: Conference
• Year: 2000
• Where: CP
• Authors: Javier Larrosa
• Keywords: Artificial Intelligence, CP 2000, Low Arity Constraints, Search Tree Size, Variable Elimination