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Subject: Re: underpromotion to rook

Author: Robert Hyatt

Date: 15:13:42 04/23/00

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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..



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