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Subject: Re: Winning Chances vs Material/Positional Evaluation

Author: Albert Silver

Date: 11:34:11 07/31/99

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On July 31, 1999 at 13:35:11, David Eppstein wrote:

>On July 31, 1999 at 11:33:59, Albert Silver wrote:
>> ...what about...situations where the defending side has a fortress with a rook
>> and a couple of pawns against which the attacking side, despite it's queen and
>> maybe a few blocked pawns, has no winning chances? The eval will certainly be
>> extremely optimistic, and understandably so, yet statistically will never
>> represent the reality of the situation. Can one make up for this sort of thing?
>
>Of course.  In the game I programmed, Fanorona, fortresses are an extremely
>important feature of the endgame.  Often, to win, you need to sacrifice some
>material to break a fortress, and yet still retain enough of a material
>advantage to clean up afterwards.  My evaluation function has code to recognize
>many commonly-occurring fortresses, and give them a bonus slightly greater than
>the amount of material needed to be sacrificed to break them, so that the
>attacking side is forced to actually make the sacrifice rather than just sitting
>around on a winning position.
>
>If fortresses occurred more frequently in chess endgames, I bet you'd see
>similar code added to chess program evaluations.  Of course, the other way of
>handling a lot of these situations is with endgame tablebases...

Yes, but what about the fortresses that cannot be won? Can the program create
them, an extremely valuable tool albeit uncommon, or recognize the possibility
in order to prevent their creation by the opponent? This would be a good basis
for a couple of test positions IMO.

                                  Albert Silver



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