Computer Chess Club Archives




Subject: Re: negascout and PVS?

Author: Fabien Letouzey

Date: 02:47:53 07/28/04

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On July 28, 2004 at 05:16:24, Russell Reagan wrote:

>On July 27, 2004 at 06:39:25, Fabien Letouzey wrote:
>>I think this difference is Bruce's own interpretation and does not represent the
>>original PVS algorithm.  I think that, in the official articles, both PVS and
>>NegaScout use what you describe as "negascout" here.
>>I might be wrong.
>>It seems Bruce's modification is an attempt to integrate the aspiration-search
>>assumption with PVS.  This is interesting.
>How is "original PVS" different from Bruce's version? I learned Bruce's version
>first... :)

OK, ignoring the PVS/NegaScout differences, normal PVS is:

1) search the first (leftmost) move with full window
2) use a scout search (null window) for all other moves

The assumption is that the first move will often be the best one.  Bruce's
assumption seems to include the aspiration-search assumption (the final score is
likely to be inside of the window).

Of course if aspiration is not used, both algorithms give the same result.


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