Searching for Macro-operators with Automatically Generated Heuristics

Abstract. Macro search is used to derive solutions quickly for large search spaces at the expense of optimality. We present a novel way of building macro tables. Our contribution is twofold: (1) for the first time, we use automatically generated heuristics to find optimal macros, (2) due to the speed-up achieved by (1), we merge consecutive subgoals to reduce the solution lengths. We use the Rubik’s Cube to demonstrate our techniques. For this puzzle, a 44 % improvement of the average solution length was achieved over macro tables built with previous techniques.