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Subject: Re: Root Position

Author: Robert Hyatt

Date: 06:45:47 01/05/01

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On January 05, 2001 at 08:05:26, David Rasmussen wrote:

>What is the best way to sort moves at the root after each iteration?

My approach is to (a) put the PV move from the previous iteration first.
Sort the remainder of the moves based on the number of nodes in the subtree
produced by each of the other moves...


>
>What is the best way adjust alpha and beta at the root after each iteration?

center it around the value returned by the previous iteration.  Look at your
output carefully to find your "swing" value.  This is the amount of score
"swing" caused only by even/odd ply searching.  If yours happens to be zero,
then just center the score on the last iteration value.  If you notice that
your odd ply searches have a score about .15 higher than even ply searches for
the same move, then factor that in.



>
>I notice I sometimes when I get a fail low at the root, I do a research, and
>then get a fail high! The most likely explanation is that I am a moron and it is
>bug. Can you think of another explanation? Or an easy way to catch this bug?

this is not common, but perfectly normal, and it can't really be avoided.


>
>Are there other issues that are important in the root position, or any "tricks"
>that one should know?
>
>Spank you.


One problem if you do null-move, is to watch for cases where a root move fails
high, then fails low on the re-search.  In that case I do _not_ make that move
a PV move.



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