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Subject: Re: Singular extensions

Author: Chris Whittington

Date: 09:20:48 01/09/98

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On January 09, 1998 at 11:45:51, Bruce Moreland wrote:

>On January 09, 1998 at 08:51:07, Amir Ban wrote:
>>On January 08, 1998 at 20:00:31, Robert Hyatt wrote:
>>>Does anyone else get a real mate here in reasonable time?  I've been
>>>extensions and none seem to be "out of control"..  However, this has
>>>been *the*
>>>hard problem for Crafty for a couple of years, so at least it now finds
>>>right move fairly quickly...
>>On P5/133 I see Qxf4 after 28 sec. and mate in 6 after 84 sec.
>>Why are singular extensions supposed to be important here ?
>This is a position where white goes down big material then wins without
>any checking moves.  He makes a series of moves that threaten mate, and
>black can do something about all of them except the last one, although
>at the end he's having to throw away material.
>A critical line for computers would be Qxf4 Bxf4 Rxh5 gxh5 Rxh5 Bh6 Rxh6
>Qg3+ Kxg3 and white is ahead material.  I might be slightly wrong about
>this line, I'm doing it from memory, but you get the idea.
>This problem has always been hard for my program for some reason, and
>Bob has the same problem.
>Interestingly, Fritz gets it pretty quickly.  You'd think that Fritz
>would have bad null move problems here, but it doesn't.
>To some other programs this position is no problem at all.  Vincent's
>program gets this in 3 plies, for instance.
>I had always assumed that other programs solved it with a mate threat
>extension, but perhaps there are other ways.
>Genius solves this problem instantaneously, and I was wondering if it
>might have something to do with this rumored singular extension thing.
>It takes mine 14 seconds on a P6/200 to find Qxf4, and I do it with a
>mate extension.  How do you do it?

Is this BT2630 position 17 ? (from the analysis above, I guess it is).

CSTal gets the key in 0 secs and the mate score in about 2 secs at 4000
nps on a p6 200.

Its done by threat detection in the evaluation function.

Chris Whittington

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