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Subject: Re: Interesting search extension data

Author: Miguel A. Ballicora

Date: 10:40:54 01/25/01

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On January 24, 2001 at 23:39:12, Robert Hyatt wrote:

>recapture is the most interesting case.  It actually appears that removing
>this _completely_ gave the best score, which is surprising since
>win at chess is a tactical suite.  Lowering this extension obviously
>speeds up the overall search.  I currently use .75 here as well.
>
>The most interesting thing is the recapture extension.  I have used it forever,
>and took the idea from Cray Blitz since I used it there as well.  I am not yet
>sure why it actually hurts since it seems (to me) to be a logical idea.  I am
>going to test this more, just for my own interest.

I have the feeling the recapture extensions could be useful in positional
tests more than in tactical. In tactical tests, most of the the time the
solution does not involved a capture and a recapture like Bx(N)c6, bxc6.
Generally, those tactical tests are tough for humans because there are
sacrifices, quiet moves, etc. but no simple trades. In fact, you might see that
you need a negative extension because the test suite is telling "this is a
simple trade! the solution is not here! do not waste your time in this
variation!"
Humans do that when they are faced with a problem rather than a typical game.
They suspect that the obvious move is not the key move. You know that the first
move most probably is not check, so you do not consider that first...
In a real game you do! I wonder if using this type of suite creates this
artifact.

In a positional test there might be a lot of those "obvious" trades as part
of important lines of the tree. Can you try and test recaptures in a
positional test? I am very curious. Thanks,

Regards,
Miguel



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