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Subject: Re: Incomplete egtbs can be harmful

Author: Uri Blass

Date: 05:02:32 11/06/01

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On November 06, 2001 at 07:18:29, Leen Ammeraal wrote:

>In the directory containing my Nalimov databases,
>when I give the command
>
>  dir kqr*.*
>
>I obtain the following output:
>
>KQRKNBB  EMD       296,182  10-04-99  2:31p KQRKNBB.EMD
>KQRKNBW  EMD       211,121  10-04-99  2:31p KQRKNBW.EMD
>KQRKQNBW EMD    21,727,039  04-11-99 11:37a KQRKQNBW.EMD
>KQRKQNBB EMD    37,812,136  04-11-99 11:40a KQRKQNBB.EMD
>
>This suggests that I have no file for the KQRkr endgame,
>which may very well be the case, since I know that
>my set of 5-man files is incomplete.
>
>I had always thought that this should not be a serious problem,
>because my program will probably deal well with KQRkr
>endgames without any egtb. However, I just found that there
>are a serious problems in the case of promotion moves,
>as in the following trivial position:
>
>[D]8/8/8/8/6r1/8/3K1kp1/R7 b - - 0 3
>
>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 is a known problem and all the commercial programs that I know had the same
problem when they started to use tablebases.

I was disappointed from it because I expected the commercial programs to test
their programs before releasing them and not after it.

The solution that was posted is also known.

Uri



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