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Planning to Guide Opening and Middle Game Play in Shogi. Reijer Grimbergen (Electrotechnical Laboratory) Hitoshi Matsubara (Future University Hakodate). Opening Databases in Two-player Complete Information Games. Two-player complete information games:
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Planning to Guide Opening and Middle Game Play in Shogi Reijer Grimbergen(Electrotechnical Laboratory) Hitoshi Matsubara (Future University Hakodate)
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
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:
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
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
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))
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.
Extension Experiment • Same 25 games against AI Shogi 2000, Kakinoki Shogi IV, Kanazawa Shogi 98 and Todai Shogi 2:
Self-Play Experiment • 100 games between three identical shogi programs: • NM: No Matching. • HM: Half Matching. • HQM: Half and Quarter Matching.
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).
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.