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Subject: Re: Ruffian quirk?

Author: Gabor Szots

Date: 00:51:01 05/23/03

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On May 22, 2003 at 20:31:37, Jay Kasick wrote:

>WHy is that sometimes when ruffian is playingand it has say a king queen and a
>pawn vs king and pawn, it will like sacrifice the queen with some stupid check
>next to the king, then run the other pawn for queen promotion?  It seems to do
>this scenerio a lot...

This behaviour is probably due to using an incomplete set of 5-man tablebases.
Ruffian (and a lot of other engines, too) is told that he can mate in n moves.
But if he promotes a pawn to queen, he may not find the corresponding tablebase,
so its score will decrease from 'mate in n' to a certain value which is big but
NOT MATE. Therefore he sacrifices the queen in order to arrive at a 4-man
position the score of which is again mate.
I hope this was clear. The main thing is that 'mate in 30 moves' is better than
a score of +20.

Regards,
Gábor



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