Richard J. Lorentz

EXPERIMENTS WITH MONTE-CARLO TREE SEARCH IN THE GAME OF HAVANNAH

Havannah is a game played on an hexagonal board of hexagons where the base of the board typically ranges from four to ten hexagons. The game is known to be difficult to program. We study an MCTS-based approach to programming Havannah using our program named WANDERER. We experiment with six enhancements of the basic MCTS algorithms and discover which are most useful for improving WANDERER. At normal time controls of approximately 30 seconds per move WANDERER can make quite strong moves with bases of size four or five, and play a reasonable game with bases of size six or seven. At longer time controls (ten minutes per move) WANDERER (1) appears to play nearly perfectly with base four, (2) is difficult for most humans to beat at base five, and (3) gives a good game at bases six and seven. 2