Rybka promotes to Bishop!!

[David Dahlem]

[Event "AEGT_Div./P4-2Ghz_40Min"]
[Site "?"]
[Date "2004.??.??"]
[Round "2"]
[White "Tinker 4.6.9"]
[Black "Rybka 1.06"]
[Result "1/2-1/2"]
[ECO "A87"]
[PlyCount "257"]
[EventDate "2004.??.??"]
[Source "W.Eigenmann"]
[SourceDate "2002.01.01"]

1. d4 f5 2. g3 Nf6 3. Bg2 g6 4. c4 d6 5. Nc3 Bg7 6. Nf3 O-O 7. O-O Qe8 8. d5
Na6 9. Rb1 e5 10. dxe6 Nc5 11. Ng5 h6 12. b4 Nxe6 13. Nxe6 Bxe6 14. Bxb7 Bxc4
15. Bxa8 Qxa8 16. Be3 Ne4 17. Nxe4 Qxe4 18. Qd2 Re8 19. Bxh6 Qxe2 20. Rfe1 Qxd2
21. Rxe8+ Kf7 22. Bxd2 Kxe8 23. Rc1 d5 24. Bc3 Bh6 25. Re1+ Kf7 26. a3 a6 27.
h4 Bf8 28. f3 c5 29. Kg2 d4 30. Bb2 d3 31. bxc5 Bxc5 32. Bc1 Be7 33. Rd1 Ke6
34. a4 Bf6 35. Bd2 Kd5 36. Rh1 Bb3 37. a5 Ke6 38. h5 gxh5 39. Rxh5 Bd5 40. Rh7
Kd6 41. Bb4+ Ke6 42. Rh1 Bc6 43. Rh6 Kf7 44. Bd2 Bd5 45. Rh1 Ke6 46. Rh5 Bc6
47. Rh6 Ke7 48. Rh1 Kd6 49. Rd1 Kd5 50. Kf2 Bd7 51. Rh1 Bd4+ 52. Kg2 Bc6 53.
Rh6 Ba1 54. Rh5 Ke6 55. Rh4 Be5 56. Kf2 Kd5 57. Rh5 Bd4+ 58. Kg2 Ke6 59. Rh6+
Kd5 60. Rh1 Bg7 61. Rb1 Bd4 62. Rb3 Kc4 63. Rb4+ Kc5 64. Rb8 Bd7 65. Rb7 Kd6
66. Bf4+ Ke6 67. Rb1 Kd5 68. Rc1 Be6 69. Rd1 Kc4 70. Bd2 Kb3 71. Be3 Kc4 72.
Rc1+ Kb3 73. Bxd4 d2 74. Rc3+ Kb2 75. f4 Kb1 76. Ra3 Kc2 77. Ra1 d1=R 78. Rxd1
Kxd1 79. Kh3 Bd7 80. Kh4 Ke2 81. Ba7 Kf3 82. Bb6 Ba4 83. Bc7 Bc2 84. Be5 Bb1
85. Bd6 Bc2 86. Bc7 Bd1 87. g4 fxg4 88. f5 Bc2 89. f6 Bb3 90. Kg5 Ba2 91. Bb6
g3 92. Bc7 Bf7 93. Kf5 g2 94. Bh2 Bc4 95. Bg1 Ba2 96. Bc5 Bf7 97. Bb6 Ba2 98.
Bg1 Bb1+ 99. Kg5 Ba2 100. Kg6 Ke2 101. Bc5 Bb1+ 102. Kg5 Ba2 103. Kf4 Bf7 104.
Bd4 Kd3 105. Bg1 Kc4 106. Ke5 Kb5 107. Kd6 Kxa5 108. Kc5 Ka4 109. Be3 a5 110.
Kd4 Kb3 111. Ke4 a4 112. Kf3 Bd5+ 113. Kf2 a3 114. f7 g1=B+ 115. Kxg1 Bxf7 116.
Kf2 Bg6 117. Bd4 a2 118. Be5 Kc4 119. Ke3 Bb1 120. Bf6 Kb5 121. Be5 Kb4 122.
Bd6+ Kb5 123. Be5 Bh7 124. Kf4 Kc6 125. Bd4 Kd5 126. Bf6 Ke6 127. Bd4 Kd5 128.
Bf6 Bb1 129. Bc3 1/2-1/2

[Sean Evans]

Hi,

It wouldn't matter, the White King could would eat any chess piece.

Cordially,

Sean

[David Dahlem]

Hi,

It wouldn't matter, the White King could would eat any chess piece.

Cordially,

Sean

The purpose of posting this game, to show that Rybka could promote to bishop at one time, but now will not. So Vas must have intentionally removed this knowledge from Rybka.

[Edmund]

Hi,

It wouldn't matter, the White King could would eat any chess piece.

Cordially,

Sean

The purpose of posting this game, to show that Rybka could promote to bishop at one time, but now will not. So Vas must have intentionally removed this knowledge from Rybka.

IIRC Vasik's public statement was that he removed that knowledge in order to fit the promotion state easier into the move variable, as it only requires 2 bits to store {no promotion, queen, rook, knight}

[bob]

Hi,

It wouldn't matter, the White King could would eat any chess piece.

Cordially,

Sean

The purpose of posting this game, to show that Rybka could promote to bishop at one time, but now will not. So Vas must have intentionally removed this knowledge from Rybka.

IIRC Vasik's public statement was that he removed that knowledge in order to fit the promotion state easier into the move variable, as it only requires 2 bits to store {no promotion, queen, rook, knight}

Makes absolutely no sense unless one extra bit makes the move not fit in 32 bits or whatever size of "move variable" type he is using. There are other ways to gain 1 bit. I believe this was done simply to reduce the size of the generated move list, since a B promotion is quite rare. Rare but still sometimes seen for good reasons (not just to promote to something that gets captured as a gesture of futility).

[M ANSARI]

A position that has a bishop under promotion as a possible non detrimental move is extremely rare, and a position where this under promotion can actually make a difference in the game being won, drawn or lost is even rarer ... so rare as to make this item not worth putting into a chess playing engine if that inclusion could have even a minute drop in ELO strength. I have yet to see a game where such an under promotion was able to save even a half point. I do think that this feature should be added to an engine in "analysis" mode, where the performance hit would be less of an issue.