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Subject: Re: KRBKPP

Author: Robert Hyatt

Date: 10:39:58 10/30/01

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On October 30, 2001 at 11:18:02, Dan Andersson wrote:

>I have to agree that it is most often correct to assume that it is a draw. But
>that was not my point. The point is that it is an inadmissible heuristic and you
>did say that it was a draw or better for black. And that is just not true is it?
>Christophe does/did something similar with the two knights (and a host of other
>endgames), maybe you do to? But I restate that it is not a fact that KRBkrpp is
>draw or win for black! And you actually did say that. Comments, or maybe a Mea
>Culpa!?

If I said it that way, it was accidental.  What I had hoped to say was that
"for Crafty, KRB vs KRanything" can't be won by the KRB side."  IE that is the
base assumption being hade here...

The counter-example position given is so very unlikely to happen (both
black pawns blockaded at f7/h7, black king can't get out of the "box", etc.
I suspect that at least for _my_ program, that position can _never_ occur
in a real game.  Somewhere within the previous 5 moves one of those pawns
would have been moved, or else the king would have left the box on f7...

I hope I never called this a "fact" anyway.  I usually call this a "heuristic"
which means something that is right in the general case, but may have exceptions
at times...

IE I suspect that in the position given, the search is more than enough to
find the direct win before the evaluation heuristic gets a chance to hide
it...  IE if you can win my rook, the heuristic doesn't apply.  Ditto if
you mate my king on the back rank...


>
>>In KRB vs KRPP the score will _never_ be positive.  It will either be zero,
>>if the pawns are not advanced very far, or less than zero if the black pawns
>>are getting advanced enough to be a problem.
>>
>>But _never_ greater than zero since white has no chances.
>
>MvH Dan Andersson



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