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Subject: Singular extensions?

Author: Jeremiah Penery

Date: 17:38:08 03/15/02

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On March 15, 2002 at 19:27:32, Slater Wold wrote:

>On March 15, 2002 at 17:59:26, Kim Roper Jensen wrote:
>
>>Hi
>>
>>Just wanted to share a position from a game I played some years ago.
>>
>>It's a position where its hard to see which side, have the best protected king.
>>
>>[D] 2r1k1nr/4ppbp/3p2p1/p3P3/bp1B1PP1/7P/qPPQ2B1/1NKR3R w - - 0 1
>>
>>How long does it take to see that white have the better position ??
>>
>>Best move here is 1.exd6!
>
>     10    18.98     ++   1. exd6!!
>     10->  49.07  -1.27   1. exd6 Bxd4 2. d7+ Bxd7 3. Qxd4 Nf6
>                          4. g5 Ba4 5. Be4 Rc4 6. Qd8# <HT>
>     11     2:01     ++   1. exd6!!
>    time=3:00  cpu=208%  mat=-1  n=245840938  fh=93%  nps=1364k
>    ext-> chk=17801393 cap=870361 pp=502965 1rep=1877028 mate=95160 sing=16
>From my (very unstable) Crafty.  As you can see, it's using singular extensions.

I tried a version of Crafty with singular extensions recently, and I always
wondered about the number given in the search statistics for singular extensions
done.  The extensions incur a very large overhead in the search (1-2 plies of
depth at least are lost), and yet only 16 nodes in the search are extended?!  I
would bet there are more than 16 singular nodes out of 245 million nodes - is
the number reported just wrong, or is that all the extension it's doing?

Jeremiah



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