Hierarchical portfolio search in prismata

Many unique challenges are faced when trying to write an AI system for a modern online strategy game. Players can control groups of tens or even hundreds of units, each with their own unique properties and strategies, making for a gigantic number of possible actions to consider at any given state of the game. Even state-of-the-art search algorithms such as Monte Carlo Tree Search (MCTS) are unable to cope with such large action spaces, as they …