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Subject: Re: How to draw a won pawn endgame

Author: Dieter Buerssner

Date: 14:31:29 05/13/03

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On May 13, 2003 at 15:55:00, Tim Foden wrote:

>On May 13, 2003 at 15:18:22, Martin Giepmans wrote:
>
>>
>>From a game Ruffian - SpiderChess
>>
>>8/7p/p2k4/1p4p1/4K1P1/P6P/8/8 b - - 0 50
>>
>>
>>
>>In this position SpiderChess played 50 .. Kc5? (it should have played
>>Ke6 Kd4 a5 -+) and thought it was winning.
>>
>>The game continued:
>>51. Kf5 Kc4 52. Kxg5 Kb3 53. Kh6 Kxa3 54. Kxh7 b4 55. h4 b3 56. g5 b2

>I'm not convinced that Kc5 is so bad.  It looks to me that 52... Kb3 was more
>likely the wrong move.  It looks to me (with brief computer assisted analysis)
>like it should have been 52... a5.

I thought the same. Actually, Yace can show a mate score after 52...a5 (with the
help of some backward analysis). I tried Kb3 as well. The score stayed around
+8, and Yace did not seem to make progress. I thought, just try to do the
suggested moves in Analyse mode fast. I expected a draw score sooner or later.
To my surprise, black won. The game went already through repetitions. When I go
back from the end position, I get a score of +14 after Kb3. I am aware, that
with advanced pawn vs Q the engine score can be very wrong. But +14 seems rather
convincing. So, the error was probably even later.

[Event "Computer chess game 60 600 +0 20 200"]
[Site "?"]
[Date "2003.05.13"]
[Round "1"]
[White "?"]
[Black "Yace 0.99.81"]
[Result "*"]
[SetUp "1"]
[FEN "8/7p/p2k4/1p4p1/4K1P1/P6P/8/8 b - - 0 50"]

50...Kc5 51. Kf5 Kc4 52. Kxg5 Kb3 53. Kh6 Kxa3 54. Kxh7 b4 55. h4 b3
56. g5 a5 57. g6 b2 58. h5 a4 59. g7 b1=Q+ 60. Kh6 Qc1+ 61. Kh7 Qc2+
62. Kh6 Qc6+ 63. Kh7 Qc2+ 64. Kh6 Qc6+ 65. Kh7 Qe4+ 66. Kh6 Qe6+
67. Kh7 Qe4+ 68. Kh6 Qf4+ 69. Kh7 Qc7 70. Kh6 Qd6+ 71. Kh7 Qd3+ 72. Kh6
Qd6+ 73. Kh7 Qe7 74. Kh6 Qf6+ 75. Kh7 Qf7 76. h6 Kb4 77. Kh8 Qh5
78. Kh7 Qf7 79. Kh8 Qh5 80. Kh7 Qf5+ 81. Kh8 Qe6 82. Kh7 Qe4+
83. Kh8 Qg6 84. h7 Qf6 85. Kg8 a3 86. h8=Q a2 87. Kh7 Qh4+ 88. Kg6
Qe4+ 89. Kh6 Qh1+ 90. Kg6 Qg2+ 91. Kf7 Qb7+ *

Regards,
Dieter



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