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Subject: Re: Meaningless Underpromotions

Author: Bruce Moreland

Date: 18:36:25 08/10/99

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On August 10, 1999 at 19:56:10, Marc Plum wrote:

>A while back I ran some multiple engine tournaments within the Nimzo99
>interface.  One thing that I noticed was that some  programs would make
>meaningless underpromotions.  That is, in a position where a promoted pawn would
>be immediately exchanged anyway, the computer might promote to a bishop or rook
>rather than a queen.  I had occasionally encountered the same thing in my own
>games with computers; I also found a small number of computer games like this
>when doing a database search for underpromotions.  I don't have any statistics
>to present; I'm just noting that this happens not infrequently.
>
>When a human player does this, he is probably just being whimsical, or it could
>be a psychological ploy.  I wonder, though, why a computer would do it.  Is it
>just a random thing?  Does the computer reason that losing a bishop is less bad
>than losing a queen, even though the resulting position is the same? Or do
>computers like messing with people's minds too?
>
>Marc Plum

To a computer 10-10=0 the same way that 3-3=0.  They don't consider the
possibility that the opponent might not recapture the promoted piece, because
the opponent will recapture the promoted piece unless they want to be down big
material.

Except in one game that my program played.  It ended up with two bishops on the
same color squares, and was unable to win a piece up.  This was a complex case
with pawns and possibly with other pieces at the start, so it's not just simply
that it didn't know that KBB vs K is a draw if the bishops are on the same color
squares.

bruce



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