Enhanced Iterative-Deepening Search

|Iterative-deepening searchesmimic a breadthrst node expansion with a series of depthrst searches that operate with successively extended search horizons. They have been proposed as a simple way to reduce the space complexity of bestrst searches like A* from exponential to linear in the search depth. But there is more to iterative-deepening than just a reduction of storage space. As we show, the search e ciency can be greatly improved by exploiting previously gained node information. The information management techniques considered here owe much to their counterparts from the domain of two-player games, namely the use of fast-execution memory functions to guide the search. Our methods not only save node expansions, but are also faster and easier to implement than previous proposals. Keywords|Heuristic search, depthrst iterative-deepening, A*, game trees, memory functions, fteen puzzle, traveling salesman problem.