Improving Strategic Play in Shogi by Using Move Sequence Trees

The main weakness of shogi programs is considered to be in the opening and the middle game. Deep search is not enough to cover the lack of strategic understanding, so most strong shogi programs use a hill-climbing approach to build castle and assault formations. The problem of a hill-climbing approach is that if the final result of two different paths is the same, then the final score will also be the same. In shogi, this leads to high priority moves being pushed down the principal variation and in extreme cases such moves will never be actually played. To solve this problem, move sequence trees are proposed, which guide the program through the right order of moves. This approach was tested in the yagura opening. A preliminary self-play experiment shows that using move sequence trees could be an enhancement of hill-climbing approaches for strategic play in shogi.