Recent Results from Analyzing the Performance of Heuristic Search

This paper extends existing analyses of the performance of heuristic search in several directions. First we show experimentally that, with minor modifications, an existing analysis of IDA* also applies to A*. Furthermore, we apply a related model to predict the performance of IDA*, using only the branching factor of the problem, the search depth, and the size of a pattern database, to the 15 puzzle. Finally, we extend this existing model to additive disjoint pattern databases. The reduction in the number of nodes expanded for IDA* using multiple additive pattern databases is the product of the reductions achieved by the individual databases. We experimentally verify this result using the 4-peg Towers of Hanoi problem. This is the first analysis of the performance of disjoint additive pattern databases.