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Subject: Re: Q. Aspiration, PVS, Fail-Soft

Author: Robert Hyatt

Date: 18:16:58 07/02/04

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On July 02, 2004 at 08:23:46, David B Weller wrote:

>Hi all,
>
>This is my first post to this forum [I have been reading it for some time]
>
>Some questions in arbitrary order:
>
>1. should PVS kick in after 1st move, or after PV found as Bruce suggests on his
>page? [I *think* tree is smaller Bruce's way]

PVS kicks in after the first move is searched at _any_ ply in the tree...


>
>2. if using fail soft, which is right: pvs(-best-1, best)  or  pvs(-alpha-1,
>alpha) ?
>
>3. depending on 2., how do you test for failure, and what bounds to use for
>research? best or alpha


fail-soft uses the same bounds as non-fail-soft.  It just allows values < alpha
or > beta to be returned, and it tries to do this intentionally at fail-low
nodes...




>
>4. Fruit uses 'mate distance prunning'  - I read in the archive [now down],
>where some suggest using shallower mate score hash entries, and others suggest
>boosting the 'draft' of mate scores [which is similar, I suppose]
>Are these all different versions of the same thing? - any help?


You _must_ use "draft" as a mate is "mate in N from the position in question"
which is different than the distance from the root.



>
>Thanks for *ALL* your help: past, present, and future;
>
>David



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