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Subject: Re: Meaningless Underpromotions

Author: blass uri

Date: 04:59:50 08/11/99

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On August 11, 1999 at 05:30:47, David Blackman wrote:

>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
>
>If two different promotions transpose to the same position in all critical lines
>(eg. the piece must be taken immediately either way) then most programs will
>choose randomly.
>
>This reminds me, a few years back IM Guy West was playing against my program
>Desperado over the board. He reached a postion where he could promote to either
>Rook or Queen and either way would work out the same. With a big smile he
>promoted to a Rook. Desperado handled it ok, but lost anyway.
>
>There are supposed to be a couple of competitive programs (but not commercial
>ones i think) that can't handle underpromotion.

There is a commercial program that does not consider underpromotions(Junior)

It has no problem to continue if the opponent underpromotes but it does not
consider underpromotions in the search

Uri



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