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 >>>checking >>>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 >>>the >>>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 ? >> >>Amir > >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? > >bruce 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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