Author: Dieter Buerssner
Date: 12:38:25 09/15/02
The following position is from a game Tiger-Yace on ICS. I watched the game, and
was happy about it first (you will find the game at the end). At some stage, I
thought, it looks really bad, and the knight of Yace may be lost. Then, there
was a trade into an endgame, with B vs. N in closed position. Yace had the
knight side, and it really seemed superior. I wondered, if it could introdude
into the white position with his K via th Q-side. I feared, that this may be
over the search horizont, but finally Yace succeeded, and had a winning
position. It showed score +8 (in favor of black) in this position:
[D] 8/8/4K1p1/4PpB1/3p1P1P/5n2/4k3/8 b - -
Now it moved Nxg5. After this move the position is a draw. It took quite a few
move, to find this out ...
I analyzed the pos later, and now and then used different chess engines. At
various points of the winning line, they all seem to fail, and spoil this to a
draw.
So, I give several test positions. The test should be, to solve them all
(otherwise it won't win). Actually each position is "avoid Nxg5". If at any
point, this is played, the game will be draw.
8/8/4K1p1/4PpB1/3p1P1P/5n2/4k3/8 b - - bm d3; c0 "Nxg5 only draws";
After d3 Kf7
8/5K2/6p1/4PpB1/5P1P/3p1n2/4k3/8 b - - bm d2; c0 "Nxg5 only draws";
After d2 e6
8/5K2/4P1p1/5pB1/5P1P/5n2/3pk3/8 b - - bm d1=Q; c0 "Nxg5 only draws";
after d1Q e7
8/4PK2/6p1/5pB1/5P1P/5n2/4k3/3q4 b - - bm Qd7; c0 "Nxg5 only draws";
After Qd7 Kf8, black has a nice winning line: Nd4 e8Q+ Ne6+ Qxe6+ Qxe6: three
checks in a row. More difficult for engines to win seems Qd7 Bf6 Ke3 Kf8:
5K2/3qP3/5Bp1/5p2/5P1P/4kn2/8/8 b - - bm Kxf4;
There are more ways to win, and what can happen here: The black side does not
want to give his Q for the pawn, and do many Q moves. In the end, it must give
the Q anyway, and it may very well end in a draw (at least with fast playing, my
engined did this stupid thing). So, I think, Kxf4 is the only convincing
immediate move.
The first position after Nxg5.
[D] 8/8/4K1p1/4Ppn1/3p1P1P/8/4k3/8 w - -
How does your engine evaluate this position? Are there any engines, that see
something close to draw value (or even say smaller 5 after some time)?
After +8 and draw, my excitement was not so big anymore. Especially, after not
long time earlier, I saw a similar, but less extreme case:
http://www.f11.parsimony.net/forum16635/messages/34505.htm
The whole game, the first position shown above was after 87. Kxe6
[Event "ICC 15 3"]
[Site "Internet Chess Club"]
[Date "2002.09.14"]
[Round "-"]
[White "Abraxis"]
[Black "Yace"]
[Result "1/2-1/2"]
[ICCResult "Game drawn by repetition"]
[WhiteElo "2653"]
[BlackElo "2586"]
[Opening "Sicilian"]
[ECO "B50"]
[NIC "SI.01"]
[Time "19:26:42"]
[TimeControl "900+3"]
1. e4 c5 2. Nf3 d6 3. c3 Nf6 4. Be2 g6 5. O-O Bg7 6. Bb5+ Bd7 7. Bxd7+ Qxd7
8. Re1 O-O 9. d4 cxd4 10. cxd4 d5 11. e5 Ne4 12. Nbd2 Nxd2 13. Bxd2 Nc6 14.
Rc1 Rfc8 15. h3 Nd8 16. Qb3 Ne6 17. Be3 a6 18. Rxc8+ Rxc8 19. Rc1 Rxc1+ 20.
Bxc1 Qc6 21. Be3 Nd8 22. Qb4 Qc7 23. Bg5 Nc6 24. Qb3 e6 25. a3 Na5 26. Qa4
b5 27. Qb4 Bf8 28. Qd2 Nb3 29. Qd1 Qc4 30. Be3 Be7 31. Nd2 Qc1 32. Qxc1 Nxc1
33. b4 Kf8 34. Kf1 h5 35. g3 Ke8 36. Ke1 f6 37. f4 f5 38. Kd1 Nd3 39. Kc2
Ne1+ 40. Kc3 Ng2 41. Bf2 h4 42. Nb3 hxg3 43. Bxg3 Ne3 44. Nc5 Bxc5 45. bxc5
Kd7 46. Bh4 Kc6 47. Bd8 Ng2 48. Bg5 a5 49. h4 Ne3 50. Bd8 Nc4 51. Kb3 Kd7
52. Bg5 Nd2+ 53. Kc3 Nf3 54. Bf6 b4+ 55. axb4 axb4+ 56. Kxb4 Nxd4 57. Bg5
Ne2 58. Kb5 Kc7 59. c6 Nd4+ 60. Kc5 Nxc6 61. Bf6 Kd7 62. Bg7 Ke8 63. Bh6 Na5
64. Kd4 Nb3+ 65. Kc3 Nc5 66. Kd4 Ne4 67. Ke3 Kd7 68. Bf8 Kc6 69. Kd4 Kc7 70.
Ba3 Kb6 71. Kd3 Ka5 72. Bf8 Nf2+ 73. Kc3 Nh3 74. Bh6 Kb5 75. Kd4 Kb4 76. Bg5
Kb3 77. Kd3 Nf2+ 78. Ke3 Kc2 79. Bd8 Ng4+ 80. Kd4 Kd2 81. Be7 Ne3 82. Bd8
Ng2 83. Be7 Ke2 84. Bg5 Ne1 85. Kc5 Nf3 86. Kd6 d4 87. Kxe6 Nxg5+ 88. fxg5
d3 89. Kf7 d2 90. e6 d1=Q 91. e7 Qd5+ 92. Kf8 Qc5 93. Kf7 Qc7 94. Kf8 Qd6
95. Kf7 Qd7 96. Kf8 Kf3 97. h5 Qd6 98. h6 Kg4 99. h7 Qh2 100. Kg7 Qb8 101.
Kf7 Qh8 102. e8=Q Qxh7+ 103. Kf6 Qh2 104. Qd7 Qh8+ 105. Kxg6 Qh5+ 106. Kf6
Qxg5+ 107. Ke5 Qe3+ 108. Kf6 Qc3+ 109. Kg6 Qe5 110. Qd1+ Kf4 111. Qf1+ Ke4
112. Qb1+ Kf4 113. Qf1+ Ke4 114. Qb1+ Kf4 115. Qf1+ {Game drawn by
repetition} 1/2-1/2
Regards,
Dieter
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