1. Planning to Guide Opening and Middle Game Play in Shogi Reijer Grimbergen (Electrotechnical Laboratory) Hitoshi Matsubara (Future University Hakodate)

2. Opening Databases in Two-player Complete Information Games Two-player complete information games: Starting position determined by the rules of the game. Opening book: Database from which early moves can be played. Vital in chess, checkers and Othello programs. Our opening book for Shogi: 1000 professional games. More than 20 books on joseki. More than 110,000 positions

3. Opening Book Use in Shogi We tested the effectiveness of our opening book in 25 games against AI Shogi 2000, Kakinoki Shogi IV, Todai Shogi 2 and Kanazawa Shogi 98:

4. Opening Book Use in Shogi Our program gets out of book quickly: Within five moves in 32 games; within ten moves in 71 games. Average: out of book after 8.5 moves. Most of the knowledge in the opening book is never used. Idea: use opening book also when there is no perfect match between the position on the board and the position in the opening book

5. Partial Matching Half matching: all of the pieces of the player to move in the current position are on the same squares as the pieces in a position in the database. Quarter matching: look only at pieces in two areas of the shogi board: i

6. Implementation If there is a full match, book move is played. No full match: both half and quarter matching. Half matching: current move number equals the move number of the position in the opening book. Quarter matching: move difference between current position and opening book position is smaller than 10. Bonuses based on the number of times the move was found: Half matching: max(0.75*PV, (0.5*PV+2*FQ)) Quarter matching: max(0.25*PV, (0.125*PV+FQ))

7. Experiments Opening book extension with partial matching: how far can the use of the opening book be extended by using our method? Self-play experiments between three identical shogi programs: No partial matching. Half matching. Half matching and quarter matching.

8. Extension Experiment Same 25 games against AI Shogi 2000, Kakinoki Shogi IV, Kanazawa Shogi 98 and Todai Shogi 2: OpponentFullHalfQuarter #Mv Played#MvPlayed AI Shogi 200010.415.876.7%19.945.2% Kakinoki Shogi IV9.012.469.4%17.347.5% Kanazawa Shogi 987.614.677.1%17.317.9% Todai Shogi 26.813.277.0%17.037.9% Total8.514.075.8%17.939.1%

9. Self-Play Experiment 100 games between three identical shogi programs: NM: No Matching. HM: Half Matching. HQM: Half and Quarter Matching. NoVersion123PWL 1HQMX54-4664-36211882 2HM46-54X63-37110991 3HN36-6437-63X073127

10. Related Work Match only with pieces in one’s own camp (Kotani 1999). Generate move sequences from an opening book (Nakaie 1996). Pattern matching with opening book (Nakaie 1997).

11. Conclusions and Future Work Conclusions: Half matching and quarter matching significantly extends the phase of the game in which the opening book can be used. Half matching and quarter matching improves the playing strength of a shogi program. Future work: Tuning of the bonus values. Finding the optimal quarter match window. Investigate other types of matching: e.g. also match the pieces of the opponent, match even smaller areas, use of similarity count.