Self-Adaptive Monte Carlo Tree Search in General Game Playing

Many enhancements for Monte Carlo tree search (MCTS) have been applied successfully in general game playing (GGP). MCTS and its enhancements are controlled by multiple parameters that require extensive and time-consuming offline optimization. Moreover, as the played games are unknown in advance, offline optimization cannot tune parameters specifically for single games. This paper proposes a self-adaptive MCTS strategy (SA-MCTS) that integrates within the search a method to automatically tune search-control parameters online per game. It presents five different allocation strategies that decide how to allocate available samples to evaluate parameter values. Experiments with 1 s play-clock on multiplayer games show that for all the allocation strategies the performance of SA-MCTS that tunes two parameters is at least equal to or better than the performance of MCTS tuned offline and not optimized per-game. The allocation strategy that performs the best is N-Tuple Bandit Evolutionary Algorithm (NTBEA). This strategy also achieves a good performance when tuning four parameters. SA-MCTS can be considered as a successful strategy for domains that require parameter tuning for every single problem, and it is also a valid alternative for domains where offline parameter tuning is costly or infeasible.