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Subject: Re: Why do programs have such a hard time with pawn promotion threats?

Author: Bruce Moreland

Date: 18:53:56 08/03/99

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On August 03, 1999 at 21:29:14, Pete R. wrote:

>Currently in the Kasparov vs. The World correspondence game there are a number
>of endgames that involve races between passed pawns on either side of the board.
>While the programs have been quite useful so far, they aren't too swift in the
>transition to the endgame when passed pawns are the issue.  Where a human player
>would push his passed pawn at every opportunity, the programs tend to diddle
>around moving pieces, until the pawn is almost promoted, when they suddenly
>realize that one side is winning. For example in the following position,
>
>8/1p1kp2Q/2np4/1p2bpB1/8/3q3P/5PP1/5RK1 w - -
>
>I ran Fritz 5.32, Hiarcs 7.32, and Crafty 16.12 for many hours, enough to get to
>18 ply for Fritz and Crafty.  All of them recommend the move g4 for white
>(Crafty switches to g4 at 15+ ply), which gets buried by b4!.  For example,
>
>27. g4 b4
>28. Qxf5 Qxf5
>29. gxf5 b3
>30. Rb1 b2
>31. Kf1 Na5
>
>and by now they will realize that white is losing.  There are a number of
>possible endgames coming up involving a race between white's passed h pawn and
>black's passed b pawn, and the programs have a real hard time with it.  What's
>going on here?

Pawns are hard to evaluate.  A advanced passed pawn can be worth anything
between nothing and a whole queen.  A rook, on the other hand, is usually worth
approximately a rook.

Queening threats are hard to evaluate because they are often long-term in
computer chess terms, they are similar to long-term sacrifices, which are
notoriously hard to evaluate.

bruce



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