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Subject: Re: Junior 8 doesn't see this simple mate

Author: Dieter Buerssner

Date: 12:56:45 08/21/03

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On August 21, 2003 at 15:20:40, Robert Hyatt wrote:

>There are ways to make it "safe".
>
>IE do it in the eval, so that if you have only a bishop, you say "that side
>can't win" and you limit the score to no more (or less depending on which side
>has the lone piece) than zero.

Yes, this will of course work in most cases, but not in all. There are some
rather long mates for the N in N vs pawns. Yace oversaw one case in a game,
where it could win in one variation by a nice B-sac on the rook file, leaving
only a knight, that would win the game. But it was too deep. (Other wins were
possible, but it was tricky, and Yace preferred to draw :-(). I use practically
the method you describe above (I give the pawn side a very small advantage in
eval).

>That way the search will find the mate _before_ the evaluation gets a chance
>to say "draw".  If you do it via "interior node recognizers" then you have to
>handle it directly or you lop the search tree off at that point and say draw
>when it is not.

Yes. All the critical cases involve a rook pawn (and/or a king already in the
corner) . So one can be lazy, and filter out that cases very easily, while still
using simple code for the interior node recognizers.

Regards,
Dieter



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