An Evaluation Function for Shogi

Shogi and chess are similar games. The aim in both games is to mate the opponent's king. However, the main di erence between shogi and chess is that in shogi pieces taken from the opponent can be used again. This has important consequences for the evaluation function. In chess the material balance is vital for the evaluation of a position while in shogi the evaluation of a position is much more based on abstract concepts like bad piece formations and danger to the king. In this paper a set of features will be proposed that are vital for an evaluation function for shogi. These features have been implemented in an evaluation function which is part of a complete shogi playing program. This evaluation function has been tested by comparing its position assessment with the opinion of professional players in 54 middlegame positions and 46 endgame positions from professional games. The evaluation function agreed with the expert opinion in 64 of these positions, judging the middlegame positions a little better (67%) than the endgame position (61%).