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Subject: Re: Incomplete egtbs can be harmful

Author: Robert Hyatt

Date: 07:21:04 11/06/01

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On November 06, 2001 at 09:35:13, José Carlos wrote:

>On November 06, 2001 at 07:23:07, Gian-Carlo Pascutto wrote:
>
>>On November 06, 2001 at 07:18:29, Leen Ammeraal wrote:
>>
>>>My program sees that black deserves a very high score,
>>>derived from the egtb, but fails to make the trivial
>>>move 1. ... g1Q because it does not find an entry
>>>for the resulting position in the egtb, and because
>>>the computed score after this promotion move
>>>is lower than the egtb score retrieved after the
>>>move Rg3, so the latter move is made and the
>>>game results in a draw instead of in a win for
>>>black. Has anyone encountered similar problems?
>>>It seems to me that for any egtb file with
>>>pawns, there should be a corresponding file
>>>for the case that one of the pawns has turned
>>>into a queen. If not, the result may be
>>>completely wrong, as in the above example.
>>>Leen
>>
>>This is wellknown.
>>
>>A possible solution is to turn off egtb's if you are in an egtb
>>position and you note that the distance to mate does not shorten
>>anymore.
>>
>>--
>>GCP
>
>  I don't understand. If the draw-by-repetition and draw-by-50-moves-rule tests
>are done correctly, this is, _before_ probing, the program will surely move the
>rook stupidly during 50 moves. Then it will see the draw, and chose another
>move. I don't see how the program can accept the draw here.
>
>  José C.


If you find that the present position (at the root) is a mate in N, but after
you try each legal move you can't find a TB score of mate in N-1, then you
_must_ have a missing TB.  Just turn the tablebases off _completely_ as the
promotion should be findable by normal search.



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