Stockfish + EGTB = Win

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muxecoid
Posts: 150
Joined: Sat Jan 30, 2010 9:54 am
Location: Israel

Stockfish + EGTB = Win

Post by muxecoid » Sun Feb 03, 2013 11:10 pm

The Critter-Stockfish TCEC game was really interesting.

Black had this:
[D]5k2/8/q4b2/8/7p/2p3N1/6P1/1Q5K b - - 0 122

But unfortunately ended with this:
[D]8/8/8/b7/8/3k2p1/6P1/7K w - - 35 148
For every player rated above 1400 the draw is obvious, but not to Stockfish without EGTB.


Offtopic:
I explored similar EGTB position in search for chess composition ideas and here is one:
[D]6k1/4K1p1/6P1/8/8/6P1/8/2B5 w - - 0 1
Mate in 9

Martin Thoresen
Posts: 1833
Joined: Wed Jun 21, 2006 10:07 pm

Re: Stockfish + EGTB = Win

Post by Martin Thoresen » Sun Feb 03, 2013 11:23 pm

Here's the game, as far as I can tell 122...c2 is a huge blunder:
[pgn][Event "nTCEC - Stage 1 - Season 1"]
[Site "http://www.tcec-chess.net"]
[Date "2013.02.03"]
[Round "3.1"]
[White "Critter 1.6a"]
[Black "Stockfish 2.31"]
[Result "1/2-1/2"]
[Variant "normal"]

1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. c3 Nf6 5. d4 Bb6 6. O-O O-O 7. Bg5 h6 8. Bh4
d6 9. Bxc6 bxc6 10. dxe5 dxe5 11. Nbd2 Re8 12. Bg3 Bg4 13. Qe1 Nd7 14. Qe2 Qe7
15. h3 Bh5 16. Rfd1 f6 17. Bh2 Nc5 18. Nf1 a5 19. Ng3 Bf7 20. b3 Rad8 21. Nf5
Qf8 22. Qc2 Rxd1+ 23. Rxd1 Rd8 24. Rd2 Rxd2 25. Nxd2 Qd8 26. Kf1 a4 27. bxa4
Kh7 28. f4 g6 29. a5 Bxa5 30. Ne3 exf4 31. Nec4 Bb6 32. Bxf4 Ba7 33. Be3 Qc8
34. Bxc5 Bxc5 35. Qd3 Be7 36. Kg1 Kg7 37. a4 Qa6 38. a5 Be6 39. Qf1 h5 40. Kh2
Qb5 41. Kh1 Qa4 42. Kh2 h4 43. Qd3 g5 44. Qe2 Qb5 45. Qf1 Bc5 46. e5 f5 47. Qd3
Be7 48. Qd4 Kf7 49. Qd3 Ke8 50. Kg1 Kf8 51. Kh1 Kg7 52. Kg1 g4 53. hxg4 fxg4
54. Qe4 g3 55. Kh1 Qa4 56. Ne3 Qxa5 57. Nf3 Qa1+ 58. Ng1 Qxc3 59. Nf5+ Bxf5
60. Qxf5 Qd4 61. Nf3 Qd1+ 62. Ng1 Bd8 63. Qc8 c5 64. Qe6 Qd4 65. Qf5 c6 66. Nh3
c4 67. e6 Bf6 68. Qh5 Qe5 69. Qf7+ Kh6 70. Qf8+ Kg6 71. Qf7+ Kf5 72. e7 Qxe7
73. Qxc4 Qe1+ 74. Ng1 Qe4 75. Qf7 Qd5 76. Qh5+ Ke6 77. Qe8+ Be7 78. Qc8+ Kf7
79. Qb7 Qd6 80. Qb1 Qg6 81. Qf1+ Kg7 82. Qe2 Qf6 83. Qe4 Qd6 84. Qg4+ Kf8
85. Qc8+ Kf7 86. Qf5+ Ke8 87. Qc8+ Bd8 88. Nf3 Qd1+ 89. Ng1 Qd5 90. Qb7 Qc4
91. Qa7 c5 92. Qb7 Kf8 93. Qd7 Be7 94. Qc8+ Kg7 95. Qf5 Qd4 96. Nf3 Qa1+
97. Ng1 Qf6 98. Qe4 Bd6 99. Qg4+ Kf7 100. Qd7+ Be7 101. Nf3 Qf4 102. Nd2 Qe3
103. Qf5+ Bf6 104. Qd7+ Qe7 105. Qd5+ Qe6 106. Qe4 Qe5 107. Qh7+ Kf8 108. Qh6+
Bg7 109. Qa6 Bf6 110. Nf1 Kg7 111. Qb7+ Kg6 112. Qb5 Qf5 113. Nd2 Qe6 114. Nf1
c4 115. Qb1+ Kg7 116. Ne3 c3 117. Qb4 Qa6 118. Qg4+ Kf8 119. Qb4+ Kf7 120. Qb1
Kg7 121. Nf5+ Kf8 122. Nxg3 c2 123. Qb8+ Kf7 124. Qc7+ Ke8 125. Qxc2 hxg3
126. Qg6+ Ke7 127. Qh7+ Kd6 128. Qa7 Qf1+ 129. Qg1 Qxg1+ 130. Kxg1 Ke5 131. Kf1
Ke4 132. Ke1 Ke3 133. Kf1 Kd2 134. Kg1 Ke2 135. Kh1 Ba1 136. Kg1 Bd4+ 137. Kh1
Be5 138. Kg1 Kd2 139. Kf1 Ke3 140. Kg1 Ke2 141. Kh1 Bf4 142. Kg1 Ke3 143. Kf1
Kd2 144. Kg1 Bc7 145. Kf1 Ba5 146. Kg1 Ke2 147. Kh1 Kd3 148. Kg1 Ke4 149. Kf1
Bd2 150. Ke2 Bg5 151. Kf1 Be7 152. Ke2 Bb4 153. Kf1 Ke3 154. Kg1 Kd2 155. Kf1
Bd6 156. Kg1 Ke2 157. Kh1 Ba3 158. Kg1 Bb2 159. Kh1 Bc3 160. Kg1 Kd3 161. Kh1
Kd2 162. Kg1 Bd4+ 163. Kf1 Bg7 164. Kg1 Bf6 165. Kf1 Be7 166. Kg1 Bd6 167. Kf1
Bb4 168. Kg1 Ke2 169. Kh1 Be1 170. Kg1 Bd2 171. Kh1 Bc1 1/2-1/2[/pgn]

gladius
Posts: 537
Joined: Tue Dec 12, 2006 9:10 am

Re: Stockfish + EGTB = Win

Post by gladius » Mon Feb 04, 2013 2:16 am

muxecoid wrote:The Critter-Stockfish TCEC game was really interesting.

Black had this:
[D]5k2/8/q4b2/8/7p/2p3N1/6P1/1Q5K b - - 0 122
Yes, this was quite unfortunate. I've added the knowledge to detect this type of draw to stockfish, we shall see if it makes it into the next version.

The rule is in KBPKP endgames, if the weaker side has a pawn on 7th rank, file B or G, the opposing bishop is on the opposite color, and the opposing king can't get closer to the pawn then the weaker king, then it's a draw.

After a depth 27 search, in the given position Stockfish now prefers Qa4 with eval of 4.72, instead of c2??.

https://github.com/mcostalba/Stockfish/pull/44.

carldaman
Posts: 1681
Joined: Sat Jun 02, 2012 12:13 am

Re: Stockfish + EGTB = Win

Post by carldaman » Mon Feb 04, 2013 5:35 am

OK, but can Stockfish detect K+ (wrong Bishop) + Rook Pawn vs lone King is a draw if the defending King can occupy the would-be queening square?

A lot of engines wrongly evaluate this as a win.

Thanks,
Carl

gladius
Posts: 537
Joined: Tue Dec 12, 2006 9:10 am

Re: Stockfish + EGTB = Win

Post by gladius » Mon Feb 04, 2013 1:05 pm

carldaman wrote:OK, but can Stockfish detect K+ (wrong Bishop) + Rook Pawn vs lone King is a draw if the defending King can occupy the would-be queening square?

A lot of engines wrongly evaluate this as a win.

Thanks,
Carl
Hi Carl,

Stockfish handles rook pawns well already (and has for some time now). So, thankfully no need to add that :).

Gary

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