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Subject: Re: mate threat extension/null move

Author: Andrew Platt

Date: 14:19:04 09/25/04

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On September 25, 2004 at 16:35:05, Stuart Cracraft wrote:

>So do you solve WAC 141 in a reasonable amount of time?

As I said, I don't see the mate score in a reasonable time but I do find Qxf4!:

 6   -178         6      45906 Kf1 b4 Bc4 Nd5 Bg5 f5
 6   -178         6      47494 Kf1 b4 Bc4 Nd5 Bg5 f5
 7   -172        26     191354 Kf1 a5 Bg5 Nd3 Qc2 Re1+ Kg2 Re8
 7   -172        28     201701 Kf1 a5 Bg5 Nd3 Qc2 Re1+ Kg2 Re8
 8   -163        89     666343 Kf1 a5 Bg5 Ne6 Bxe6 Rxe6 Kg1 f5
 8   -163        92     692725 Kf1 a5 Bg5 Ne6 Bxe6 Rxe6 Kg1 f5
 9   -124       823    6360825 Kf1 Rc8 Qb1 Nd5 Kg1 b4 Bg5 Be7 f4
 9   +137      1218    9592419 Qxf4 ++
 9   +764      1459   11570166 Qxf4 Bxf4 Rxh5 gxh5 Rxh5 Bh6 Rxh6 Qg3+ fxg3 Re2+
Kh3 Rh2+ Kxh2 a5
 9   +764      1462   11596859 Qxf4 Bxf4 Rxh5 gxh5 Rxh5 Bh6 Rxh6 Qg3+ fxg3 Re2+
Kh3 Rh2+ Kxh2 a5
10   +764      1834   14726581 Qxf4 Bxf4 Rxh5 gxh5
10   +764      1870   15025646 Qxf4 Bxf4 Rxh5 gxh5

As you can see it misses the mate near the bottom. It extends at Rxh5 (mate
threat), Rxh5 again, Rxh6 (mate threat still), Qg3+ (check). I forget exactly
why it misses the mate at the bottom. I know it drops into qsearch with Rh8#
being move it doesn't consider because it's a capture; I think the line it comes
up with happens because it has the most extensions and captures!

I don't consider this conclusive; I expect I could change the search for
something else and find this one disappears again!

Andy.



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