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Subject: Re: Draw recognition by eval problems

Author: Simon Finn

Date: 10:51:55 10/17/01

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On October 17, 2001 at 06:19:46, Rafael Andrist wrote:

>[D]6k1/8/7P/3pK3/8/8/2B5/8 w - - 0 1
>
>As most of the others, my program knows that KBP-K with a rook pawn and bishop
>of wrong colour is drawn if some conditions are met. In the position given above
>black has also pawn and the position remains a theoretical draw. Now, my program
>evaluates it as +3.5 and refuses to capture the black pawn. Of course I could
>add this special case too but there are lots of other combinations of pieces I
>had to add too. Did someone try a more general attempt to solve this problem?
>Would the following rule work in this case? If White is ahead in material and if
>it is a drawn KBP-K position after removing all black pieces, the position is a
>draw.

There are some positions where adding a Black pawn on g7 (vs White pawn on h5)
or g6 (vs White pawn on h6) to converts a KBPKP draw to a loss by obstructing
the Black king.

There are lots of positions where adding 2 Black pawns (h+g or doubled g pawns)
allows White to win. For example:

[D]8/8/1k6/1p1K4/1p3B2/8/P7/8 w - - 0 1 bm Bd2 c0 "Kling & Horwitz 1851 (Fine
#152)"

[D]8/4k1p1/6Bp/7P/8/2K6/8/8 w - - 0 1 bm Kd4 c0 "Walker 1841 (Fine #153)"

>
>The problem are IMO possible Zugzwang positions which could occur, at least in
>other types of drawn endgames with big material imbalance, e.g. KQ-KP. In this
>case a theoretically drawn position could converted to a lost in some cases if a
>black piece is added.

That's what happens in both the above studies.

I don't know any such cases where Black has no g-pawn. Perhaps that could be the
basis for a generalised rule?


Simon




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