R232
On the Impact of Subproblem Orderings on Anytime AND/OR Best-First Search for Lower Bounds
William Lam, Kalev Kask, Rina Dechter, and Javier Larrosa

Abstract
Best-first search can be regarded as anytime scheme for producing lower bounds on the optimal solution, a characteristic that is mostly overlooked. We explore this topic in the context of AND/OR best-first search, guided by the MBE heuristic, when solving graphical models. In that context, the impact of the secondary heuristic for subproblem ordering may be significant, especially in the anytime context. Indeed, our paper illustrates this, showing that the new concept of bucket errors can advise in providing effective subproblem orderings in AND/OR search.

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