An upper bound on the time complexity of iterative-deepening-A*

Abstract

This paper establishes an upper bound on the time complexity of iterative-deepening-A* (IDA*) in terms of the number of states that are surely-expanded by A* during a state space tree search. It is shown that given an admissible evaluation function, IDA* surely-expands in the worst caseN(N+1)/2 states, whereN is the number of states that are surely-expanded by A*. The conditions that give rise to the worst case performance of IDA* on any state space tree are described. Worst case examples are also given for uniform and non-uniform state space trees.