A Lookahead Strategy for Heuristic Search Planning

Relaxed plans are used in the heuristic search planner FF for computing a numerical heuristic and extracting helpful actions. We present a novel way for extracting information from the relaxed plan and for dealing with helpful actions, by considering the high quality of the relaxed plans in numerous domains. For each evaluated state, we employ actions from these plans in order to find the beginning of a valid plan that can lead to a reachable state. We use this lookahead strategy in a complete best-first search algorithm, modified in order to take into account helpful actions. In numerous planning domains, the performance of heuristic search planning and the size of the problems that can be handled have been drastically improved.

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