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Subject: Re: Endgame trap; some progs see it - Fritz looking stupid again

Author: José de Jesús García Ruvalcaba

Date: 16:32:02 05/26/99

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On May 26, 1999 at 13:30:47, James Robertson wrote:

>On May 26, 1999 at 13:09:05, Paul Richards wrote:
>
>>On May 26, 1999 at 08:42:07, eric guttenberg wrote:
>>
>>>This is an interesting trap from a real gm game (Chandler-Z. Polgar, 1987):
>>>
>>>White  K on e6  B on e4  P's on g5 and h2
>>>Black  K on g7  N on g8
>>>Black to move
>>>
>>>In this losing position Black played 1...N-h6; White played 2.gxh6ch?? and
>>>was forced to accept the draw after Black played 2...K-h8!
>>
>>Of the engines I have running under Fritz, the following handle this
>>easily: Crafty 16.1, Crafty 16.6, LGGold 2.0, Doctor?3.0, and a couple
>>versions of Comet.  Exchess 2.50 and 2.51 have no clue, and neither does
>>Fritz 5.32, which is sad as Fritz is one of the top programs.  So why
>>is Fritz being stupid again??
>
>My program has no clue either. I think the depth required to see that there is
>nothing better than repetition is quite high (my program did not see the
>repetition after 14 plies), and unless you have special knowledge, a program
>will not solve this one.
>
>James

	The main problem is that no program will see the repetition, as white can
easily make 50 moves without allowing a third repetition. The program would need
to detect the 50-moves draw with the search, and that would not be enough as
white can make five pawn advances, resetting the count.
	Then the program needs to search 50x5x2=500 plies to detect the draw, and that
is quite far from what current programs reach on current hardware.
	Of course a complete set of five men tablebases will handle this position, but
no program has them yet, and it would not help if we add another white pawn on
the h-file.
José.



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