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

Author: Ross Boyd

Date: 03:52:55 08/02/03

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On August 01, 2003 at 03:31:15, Richard Pijl wrote:

>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.

I thought about storing mate scores as exact but the possibility of there being
a shorter mate worried me. So I just store them as a HIGH bound.

Do you find any side effects with doing it your way?

Thanks Richard,

Ross





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