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Subject: Re: new thoughts on verified null move

Author: Robert Hyatt

Date: 07:41:01 11/24/02

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On November 23, 2002 at 08:11:37, scott farrell wrote:

>Just after other people's thoughts.
>I think Omid's work overlooked the adapative null move searching many of us do,
>ie. transitioning from r=3 to r=2.
>I think adaptive null move tries to GUESS where to use r=2 to reduce the errors
>that R=3 makes. I guess it depends on how often this GUESS is correct, the cost
>of the verification search, and how long it takes the adaptive searching to
>catch the error at the next ply.
>Has anyone looked at setting the verification search to reduced depth of 2
>(rather than 1)? obviously to reduce the cost of the verification search.
>Robert : How did your crafty implmentation go?

I have not had time to finish it yet.  We've been ordering a bunch of new
machines, my ftp machine developed a disk error, a lab was broken into and
some minor equipment stolen, etc.  Hopefully I will get a chance to work on
it some more tonight.

>I know that measuring nodes for a fixed search depth sounds like good science,
>but I think you really need to look at where one method makes a mistake, and how
>quickly it can find the mistake at the next ply. Obviously my point is if it
>finds a given move with less nodes, thats good, if it takes an extra ply of
>search, sometimes that's acceptable if we can catch it quick enough. We've all
>seen how quickly at the next ply a fail low is often fast, well that is my major
>"verification search" for ALL search problems - horizon, null move, etc etc. I
>think it might be better to include some nodes from the next iteration, where
>the next ply fails low really really quickly, and finds the mistake anyway,
>maybe consider the nodes as part of the previous ply.

Whether it works or not is probably going to depend on the program.  Which is
not unexpected.  I think that most of the null-move errors happen right at the
border where the search collapses to a q-search only.  This might help some
of them (but not the ones where R-1 also collapses to a q-search only.)  And it
will obviously handle the cases where zugzwang plays a big role, such as in
endgames, which might allow null-move to be turned on always...

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