Computer Chess Club Archives




Subject: Mate Extensions (Re: Singular extensions)

Author: Ernst A. Heinz

Date: 13:23:11 01/09/98

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On January 09, 1998 at 13:54:00, Bruce Moreland wrote:

>The trick is detecting that you are getting mated if you do nothing.  I
>am already doing a null move search, which will fail low because the
>opponent has a threat.  The problem is to figure out how low it is
>failing.  I try to return scores that are outside the alpha-beta bounds
>when I can, and sometimes I catch a -MATE here, and in those cases there
>is obviously a mate threat.  I am sure there are other ways, lots of
>ideas to try.

Hi Bruce,

Thank you very much for the detailed explanation and your willingness
to share ideas.

If I understand you correctly, your "mate extension" looks like a
specialization of Donninger's 1993 fail-low "deep search" extension
applied everywhere in the tree and not just near the leaves.

Really cute!

"DarkThought" has used "deep search" extensions for a while now and
I still like them very much although Donninger does no longer use them.
Making them sticky, however, did not gain anything in our

The fact that "DarkThought" did not terribly suffer from null-move
related mating problems is probably due to our "deep search" extensions.


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