Common Misconceptions Concerning Heuristic Search

Abstract

This paper examines the following statements about heuristic search, which are commonly held to be true:

• More accurate heuristics result in fewer node expansions by A* and IDA*.
• A* does fewer node expansions than any other equally informed algorithm that finds optimal solutions.
•  Any admissible heuristic can be turned into a consistent heuristic by a simple technique called pathmax.
• In search spaces whose operators all have the same cost A* with the heuristic function h(s)=0 for all states, s, is the same as breadth-first search.
• Bidirectional A* stops when the forward and backward search frontiers meet.

The paper demonstrates that all these statements are false and provides alternative statements that are true.