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Subject: Re: An algorithm for KBN vs. K

Author: David Dahlem

Date: 06:18:20 09/05/04

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On September 03, 2004 at 21:10:03, Robert Hyatt wrote:

>On September 03, 2004 at 18:49:27, Alessandro Scotti wrote:
>
>>I was trying to teach my engine this ending, and so far I haven't found a
>>solution I really like. I more or less know how the ending should be played, and
>>my attempts mainly focused on moving the lone king towards the "bishop corner"
>>and the other king in a sort of opposition. While I was tuning the parameters, I
>>noticed how slow is progress in some positions. In this one:
>>
>>[D]8/8/8/3k4/8/8/8/3BN2K w - - 0 1
>>
>>GNUChess takes 44 moves to mate, I gave up even earlier as pieces seemed to move
>>without a logic.
>>So I have two questions now, the most important: how should this ending be
>>played, exactly? Would it be useful (i.e. lead to a faster mate) to have say a
>>two-stage code where we first gain the center of the board and then push the
>>other king to the corner?
>>And the second one: using the EGTB for this ending, would it be possible to
>>analyze the paths that lead to mate and automatically generate good coefficients
>>to help an algorithm (or actually almost piece-square) based solution?
>
>
>All you need is an evaluation that will do the following:
>
>1.  drive the losing king to the edge of the board, using all three pieces to do
>so so that all three pieces are "close to the action."
>
>2.  drive the losing king to the corner attacked by the bishop.
>
>A 3-4 ply search is enough to do this, although not "optimally"...

What about when your engine is on the losing side of a kbnk ending? Does Crafty
have code to try to avoid the kbnk mate, if possible until the 50-move rule?

Regards
Dave



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