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

Author: Pete R.

Date: 16:03:25 08/04/99

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On August 04, 1999 at 14:57:02, José de Jesús García Ruvalcaba wrote:

>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?
>
>	I recommend to use crafty 16.15 with 'extension pushpp 1.0' for this and
>similar positions, it will extend more aggresively on passed pawn advances (the
>default is 0.75), and will see the dangers at shallowers depths.
>	I can not do it myself because I do not have "many" hours of computer time
>available.
>José.

Thanks, I'll play with these new parameters.  I think the ppscale might be the
one to use vs. the extension, but I'll have to fiddle with it.



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