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

Author: Ross Boyd

Date: 03:46:15 08/02/03

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On August 01, 2003 at 09:58:45, Robert Hyatt wrote:

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

>>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.
>
>You are mixing apples and oranges.  Suppose you get a hash hit with an
>EXACT indicator, but it is outside the alpha;/beta window.  What would
>you store for such a position later?  Answer = EXACT.  Because it is an
>exact score.  An EGTB hit is the same.  It is not the result of an alpha/
>beta search below this position with the current bounds in force, it is
>the result of a _complete_ search from this position.

So, any time we KNOW the true score we can store it as an EXACT bound...

And further, you're saying any backed up score which was retrieved with an EXACT
score should also be saved as an exact score...

That suggests to me that I should change search() and quiesce() to return a
structure which contains the score AND whether its an EXACT score...

Am I understanding you correctly?

I imagine that this would increase the population of exact scores in the hash
table and result in a lot more early cutoffs....



>
>Complete searches always produce EXACT scores.  Searches with an alpha/beta
>bound to speed up the search only produces an EXACT score when the score lies
>within the alpha/beta window.
>

Yep, agreed.

Thanks for your help Bob. This has given me some more food for thought....

Ross









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