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Subject: Re: Kortchnoi - Rechlis

Author: Dieter Buerssner

Date: 11:52:01 11/15/01

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On November 15, 2001 at 06:51:23, José Carlos wrote:

>>[D] 8/8/6p1/6Q1/2K4p/6kP/5p2/8 b - - 0 55

>  This is the kind of position programs can chose the right moves, but don't
>understand at all. My program says +7.xx for white, but it defends correctly
>with black.

Yes.

>  I guess this position won't be solved by any program in a long time because it
>requires reasoning. You can't write code for positions like this easily, because
>an extra pawn here or there makes a difference.

Certainly not easy. But this has bothered me for a while. I have seen it in
games of Yace, and just accidently I saw this game yesterday.

Perhaps a naive idea would be: Dectect the cases of drawn Q vs. P (R or B-P on
7th rank and some rules for K positions). If all pawns of the Q-side are
blocked, it gets tricky. When from no blocking pawn a check can be given, or the
promotion square can be controlled, give the P on 7th the value of the Q. It is
of course still no guarantee for draw, because the Q side may be able to force
the promotion, exchange Qs and have a won pawn endgame.

Perhaps a table with all such blocked pawn positions. Or some special table
base.

Perhaps also a special search rule, although this won't be easy. When I play
against Yace in the above position after about 20 moves, I get a draw score.
When I go back, immediately a draw score is seen for any move almost until back
to the position (Yace remembers the positions together with search depth and
score, that where analyzed). Only at one point, where the move Qxg6 was, this
capture will be avoided, again with a bogus high score for white. When I do
again about 10 moves forward I see the draw score again. No I can go back until
the root, and the draw score will be seen there. This is a totally mechanical
manner - so it should be possible to do this automatically. I think, essentially
some sort of tablebase will be built for this position.

Cheers,
Dieter




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