A space-time tradeoff for memory-based heuristics

A memory-based heuristic is a function, h(s), stored in the form of a lookup table (pattern database): h(s) is computed by mapping s to an index and then retrieving the appropriate entry in the table. (Korf 1997) conjectures for search using memory-based heuristics that m.t is a constant, where m is the size of the heuristic's lookup table and t is search time. In this paper we present a method for automatically generating memory-based heuristics and use this to test Korf's conjecture in a large-scale experiment. Our results confirm that there is a direct relationship between m and t.