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Subject: Re: Fruit - Question for Fabien

Author: Fabien Letouzey

Date: 09:56:37 03/11/04

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On March 11, 2004 at 12:40:40, Dan Honeycutt wrote:

>Can you explain your statement in an earlier thread "I never "hash cut" at PV
>nodes (I only read the best move) so that my PV is never truncated."

>At the start of each iteration i save the pv from the previous iteration and set
>a flag.  while the flag lasts i use it to order moves and avoid hash cuts.
>however, once the old pv plays out and the flag is cleared any new pv is
>(likely) truncated.  do you have a way around that?

So you flag the "leftmost branch" only right?  If one of your PV move is wrong
(another one is found to be better), you "lose" the flag, is that it?  This
reminds me of a non well-known algorithm called P-alpha-beta which is a hybrid
between alpha-beta and PVS.  It is interesting in itself, but I disgress ...

If you use a PVS variant, a common way of knowing that the current node type is
"PV node" is to test if (beta!=alpha+1) (non-null window, this assumes you are
using PVS).  If you never apply hash cuts at those nodes, your PV should always
be complete.

Note that this may be affected by "window reductions" (aspiration, "shrunk"
window after a re-search failed high, ...).

But the short answer is (beta!=alpha+1) :)  If you don't use PVS, then you can't
predict in advance if the current node is going to be PV or not of course :)

Maybe I did not understand your question correctly, don't hesitate asking for
more precision.

Fabien.




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