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Shogi and Realization Probability search

Shogi and Realization Probability search. Hashimoto Tsuyoshi JSPS Research Fellow. Chess, Shogi and Go. Average number of possible moves Go > Shogi > Chess Chess = simple (brute force was enough for beating human champion!) Shogi = complex ( ← reuse of captured pieces)

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Shogi and Realization Probability search

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  1. Shogi and Realization Probability search Hashimoto Tsuyoshi JSPS Research Fellow Hashimoto Tsuyoshi

  2. Chess, Shogi and Go • Average number of possible moves Go > Shogi > Chess Chess = simple (brute force was enough for beating human champion!) Shogi = complex ( ←reuse of captured pieces) Go = shogi’s experience is useful!! (I wish) Hashimoto Tsuyoshi

  3. My Shogi program Tacos • Realization-Probability Search [Tsuruoka, 2001] • Df-pn (mating search) [Nagai, 2000] • SPH (brinkmate search) [my Ph.D Thesis, 2001] Hashimoto Tsuyoshi

  4. My current 2 problems • When call mating search? • What is good category? (= To find good shape of search) Hashimoto Tsuyoshi

  5. Low probability High probability stop Realization-Probability (R-P) Search Tree Threshold = 0.1 Move probability Deeper & Wider Shallower & Narrower Realization probability = Position probability Hashimoto Tsuyoshi

  6. Move Probability Our program = 2500 category • Calculate from many games records • Category (Shogi) Check, capture piece, attack, promotion… • Category (Go) Atari, Take stones, Tsuke, Kakari, …? Hashimoto Tsuyoshi

  7. Why R-P search is effective? • Systematic and statistical • Simple search algorithm ⇒ Complex games = tuning parameters by hand is too difficult! • Search deeply after important moves • Drastically reduce search after unimportant moves ⇒ Complex games = Courage to stop searching is important!! Hashimoto Tsuyoshi

  8. Advanced category 1 “Just before” group • Just before capture, just before escape, just before attack ex: Capture with high gain (pawn): normal = 40.3% just before = 85.9% Hashimoto Tsuyoshi

  9. Advanced category 2 History Analysis • Renda no Fu (re-attack pawn) 3.1%⇒15.4% • Hashizeme Fu tarashi (put pawn at edge after sacrifice of pawn) 0.2%⇒9.3% Hashimoto Tsuyoshi

  10. Advanced category 3Okuri no Tesuji • ▲2二金（22gold) Before After ( check with loss) (Okuri no Tesuji) 0.592% ⇒　 5.44% Hashimoto Tsuyoshi

  11. Advanced category 4 Area Analysis Move of pieces on board • Come close to opponent king, soppo (keep off from opponent king) Put captured pieces • Around opponent king, Around self king, normal Normal → Soppo 1～2%→0~0.3% Hashimoto Tsuyoshi

  12. Experiment • With History Analysis + Okuri v.s. • Without History Analysis + Okuri 61-38-1 • With Area Analysis v.s. without 58-42 Hashimoto Tsuyoshi

  13. Conclusion • RPsearch = good for Go? • Advanced categories Pick up good category from big category of low probability! (or Pick up bad category from big category ) Hashimoto Tsuyoshi

  14. Future (Current) work • Make programs stronger for tournaments (Computer Olympiad, Nov. GPW cup, Nov. The World Computer Shogi Championship, May.) Hashimoto Tsuyoshi

  15. About Me Date of birth: September 17, 1970 Place of birth: Kyoto City, Japan (Old capital, 794 – 1869) Language: Japanese >> Chinese(mandarin) > English Hobby: Shogi (4 dan, Rating 2100-2200 = level of amateur champion in a city) , Travel, Camp Ph.D: March 2002, Shizuoka University, Hamamatsu, Japan (about Shogi Endgame, brinkmate search) Programs: Shogi (Tacos), LOA ((T-T)), AMAZONS(ASKA), 4 persons Shogi (HIRA)… Big Goal: Defeat Meijin (Champion of proffesional Shogi player) Hashimoto Tsuyoshi

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