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Subject: Re: Bug in CHEST - CHEST doesn't see a mate in 2

Author: leonid

Date: 07:34:29 04/28/02

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On April 28, 2002 at 08:00:15, Vincent Vega wrote:

>Simplified position to show the bug:
>[D]8/8/8/8/8/8/4KP2/R1Qn3k w - - 0 1
>
>This is a mate in 2 (1. Qxd1+).
>
>But CHEST says:
>
>CHEST version 3.19, 18-Dec-1999
>Input file: 'xx'
>Reading job:
>#	xx
>W:  Ke2 Qc1 Ra1 Pf2 (4)
>B:  Kh1 Nd1 (2)
>FEN: 8/8/8/8/8/8/4KP2/R1Qn3k w - -
>analysing (mate in 2 moves):
>No solution in 2 moves.
>refu  1: Qxd1+   --      [  1-]   M2: move
>refu  2: Qc6+    --      [  1-]   M2: move
>refu  3: Qh6+    Kg1     [  1-]
>refu  4: f3      --      [  1-]   M2: move
>refu  5: f4      --      [  1-]   M2: move
>refu  6: Rb1     --      [  1-]   M2: move
>refu  7: Ra2     --      [  1-]   M2: move
>refu  8: Ra3     --      [  1-]   M2: move
>refu  9: Ra4     --      [  1-]   M2: move
>refu 10: Ra5     --      [  1-]   M2: move
>refu 11: Ra6     --      [  1-]   M2: move
>refu 12: Ra7     --      [  1-]   M2: move
>refu 13: Ra8     --      [  1-]   M2: move
>refu 14: Qb1     --      [  1-]   M2: move
>refu 15: Qc2     --      [  1-]   M2: move
>refu 16: Qc3     --      [  1-]   M2: move
>refu 17: Qc4     --      [  1-]   M2: move
>refu 18: Qc5     --      [  1-]   M2: move
>refu 19: Qc7     Kg1     [  1-]
>refu 20: Qc8     --      [  1-]   M2: move
>refu 21: Qd2     --      [  1-]   M2: move
>refu 22: Qe3     --      [  1-]   M2: move
>refu 23: Qf4     Kg1     [  1-]
>refu 24: Qg5     --      [  1-]   M2: move
>refu 25: Qb2     --      [  1-]   M2: move
>refu 26: Qa3     --      [  1-]   M2: move
>refu 27: Kd2     --      [  1-]   M2: move
>refu 28: Ke1     --      [  1-]   M2: move
>refu 29: Kf3     --      [  1-]   M2: move
>refu 30: Kxd1    --      [  1-]   M2: move
>refu 31: Kf1     Ne3+    [  1-]
>refu 32: Kd3     --      [  1-]   M2: move
>Time (virt) = 0.000 sec

I doubt very much that it is some bug in Chest. I verified with this program
huge number of extremely tough positions and it never fail. It could be that
your indication to the program was not what it should be.

I tried this position with my mate solver, LLchess. It confirm mate exactly in 2
moves. White queen take black knight. Black side have after this two moves. Both
of them by black king. After each of them white Queen make immediate mate.

Only it is true that I am not sure about significance of "w - - 0 1", and maybe
everything is only in this small difference. My solver looked into this position
as one that have no rock for white or black side.

Leonid.



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