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Subject: Re: Bounds... when is an exact score an EXACT score?

Author: Richard Pijl

Date: 00:31:15 08/01/03

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On August 01, 2003 at 02:33:13, Ross Boyd wrote:

>Hi all,
>
>I want to get a clear definition of hash table bounds...
>
>So, this is what I understand...
>
>When we get a score during search, one of 3 things can happen:
>
>1. The score is >= beta... so we store this as a LOW_BOUND.
>2. The score is <= alpha... so we store this as a HIGH_BOUND
>3. Or its between alpha and beta... so its an EXACT score.
>
>So the definition of an EXACT score is anything we find between alpha and
>beta...
>
>So far so good....
>
>Ok, what about an EGTB probe? A successful EGTB probe returns a true score
>whether it be a draw or the number of moves to mate.
>
>By applying the 3 rules above I SHOULD store the EGTB score as a LOW, HIGH or an
>EXACT bound...  Is that correct?
>
>Why not store it as an EXACT score?  (Its as exact as you're going to get...)
>Will the ab search break in some subtle way if I do this?

No problem with that.
I even have a special kind of EXACT score: Absolute truth ;-)
I store EGTB probes like that and also matescores with depth>distance to mate.
These scores will be used even when the depth of the entry is not sufficient.
Richard.




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