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Subject: Re: Unusual Crafty behavior ?!

Author: Robert Hyatt

Date: 21:29:28 11/18/01

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On November 18, 2001 at 12:09:10, Jeff Lischer wrote:

>On November 18, 2001 at 10:03:15, piet de hoop wrote:
>
>>The next position occured in Diep versus Rebel Century 4 round 6 of the Dutch
>>Open Computer Chess 2001
>>
>>[D] 8/6p1/3k3p/8/3K4/7P/8/8 b - - 0 43
>>
>>The result was a draw, but for some computerprograms I tried, the evaluation was
>>from -1 to -3.4 pawn. (Fritz 6.0, Crafty,Yace)
>>
>>I expect that programs equipped with the right pawntable base have no problem
>>with this position, but i expected that programs without these tablebase while
>>calculating over 30 plys or more should give the right evalution?
>>
>>Or do i miss something?
>>
>>Piet
>
>When I tried this position with programs using all 3,4, and 5 piece tablebases
>they saw the draw immediately.
>
>The only oddity was Crafty. I was using Crafty 18.12 in WinBoard 4.2.3. When
>Crafty played White, it saw the draw in tablebases and moved immediately. When
>it was Black, however, it did not see the draw in tablebases. Instead it anayzed
>the position as it normally would and gave Black a 2-3 pawn advantage. Other
>programs (Yace, Gandalf) worked fine in WinBoard as both White and Black.
>
>Is this the intended behavior for Crafty or a bug? If it is intended, why?


Normal.  It is called "swindle mode" and can be turned off with "swindle=off"
in the crafty.rc file.

The idea is that if you are ahead in material, but it is drawn, it is better
to search and keep the material waiting for an opponent mistake, rather than
giving up the extra material into an even easier-to-draw position.

This has been discussed here dozens of times...



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