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Subject: Re: Dr. Hyatt, have you decided to keep the VR change in Crafty?

Author: Robert Hyatt

Date: 13:37:36 12/18/02

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On December 18, 2002 at 16:28:09, Dezhi Zhao wrote:

>I read some days ago you experimented the verified null move idea with Crafty
>and some encouraging results. However, have you decided to keep the change?
>I think the VR=3 search is more akin to R=3 search in the long run. This idea
>seems to me is that you verify with reduced depth a likely cut node that was
>detected by a fast R=3 null move search. Though cheap screening (R=3) and
>expensive verification (reduced depth search) sounds a reasonable trade-off, all
>the sub-nodes of the verfication are still searched by using the less-reliable
>R=3 again.  The verification could fail the same way as standard R=3 to some
>less extent. I think the validation process of the verified null move
>in a real program like Crafty could be lengthy.

I haven't decided anything yet.  It seemed better in some cases, worse in
and overall seemed to be a "break-even" on the first implementation.  I got
tracked with the hyper-threading stuff and this new machine, and final exams and
projects, so I haven't played with it any more recently...

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