Hierarchical heuristic search revisited

Abstract

Pattern databases enable difficult search problems to be solved very quickly, but are large and time-consuming to build. They are therefore best suited to situations where many problem instances are to be solved, and less than ideal when only a few instances are to be solved. This paper examines a technique - hierarchical heuristic search especially designed for the latter situation. The key idea is to compute, on demand, only those pattern database entries needed to solve a given problem instance. Our experiments show that Hierarchical IDA* can solve individual problems very quickly, up to two orders of magnitude faster than the time required to build an entire high-performance pattern database. © Springer-Verlag Berlin Heidelberg 2005.