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Subject: Re: I hate null moves

Author: Tord Romstad

Date: 10:11:17 01/31/04

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On January 30, 2004 at 16:09:51, Ed Schröder wrote:

>I can imagine my way of doing things is confusing, maybe when I tell a little
>about Rebel's history you will understand better.
>
>In the past (before 2001 or so) Rebel was a full static selective search
>program. Every node in the tree is evaluated and the score is used as a base to
>prune the tree.
>
>And now nullmove moves in, in the case the selective search returns the message
>to prune I call nullmove with as only reason to verify if it is safe to prune.
>If nullmove returns a score >= alpha the node is searched after all. So I use
>nullmove to verify my static selective search.

Thanks.  Seems rather similar to the "lazy verification searches" I experimented
with
recently, which I ended up discarding.  I should probably give it another try.

>Nullmove is only practiced in the very few plies of the search, iteration
>driven. It takes out the worst failures of my static selective search.
>
>With a simple parameter I can make Rebel a standard R=2 or R=3 program, it then
>runs 2 times slower and loses considerable against the default setting.
>
>Hope this helps.

Yes, I hope I understand it better now.  I hope to find the time to do some
experiments
next week, and will contact you again if I have further questions or discover
some
interesting ideas

Thanks for your help,
Tord



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