Move pruning and duplicate detection

Abstract

This paper begins by showing that Burch and Holte's move pruning method is, in general, not safe to use in conjunction with the kind of duplicate detection done by standard heuristic search algorithms such as A*. It then investigates the interactions between move pruning and duplicate detection with the aim of elucidating conditions under which it is safe to use both techniques together. Conditions are derived under which simple interactions cannot possibly occur and it is shown that these conditions hold in many of the state spaces commonly used as research testbeds. Unfortunately, these conditions do not preclude more complex interactions from occurring. The paper then proves two conditions that must hold whenever move pruning is not safe to use with duplicate detection and discusses circumstances in which each of these conditions might not hold, i.e. circumstances in which it would be safe to use move pruning in conjunction with duplicate detection. © 2013 Springer-Verlag.