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Subject: Re: underpromotion to rook

Author: David Blackman

Date: 03:07:36 04/25/00

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On April 24, 2000 at 22:34:28, Dann Corbit wrote:

>On April 23, 2000 at 18:13:42, Robert Hyatt wrote:
>
>>On April 23, 2000 at 17:15:52, Michael Fuhrmann wrote:
>>
>>>Why would a program ever underpromote to a rook? Saw Crafty do this recently.
>>>(In this particular case, it had no impact on the outcome of the game.)
>>
>>
>>1. it is necessary at times.  IE if you promote to queen, you stalemate your
>>opponent.  if you promote to rook, you can still win without stalemating him.
>>
>>2.  In the case of chess engines, it is pretty common to see this.  The most
>>common reason is that the =R is not a check, when the =Q is a check, or the
>>rook allows fewer checks later in the tree.  So by promoting to a rook, it
>>avoids some tactic that it really can't avoid...  IE this is a horizon effect
>>situation..
>
>Are there any cases where you would promote to bishop or rook to achieve
>stalemate for yourself?  (e.g. you are far behind in material (say down two
>queens or more), and the only legal move is the pawn promotion or something of
>that nature)

I've seen carefully constructed problem positions where underpromoting to rook
or bishop was the only way to get a draw. I don't have any examples handy.

There are supposed to have been about 10 master games played where
underpromotion to rook or bishop was played and was actually the best move in
the position. Not sure how many were to achieve a stalemate draw and how many to
win. The only real game position i saw was promote to bishop to win.



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