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Subject: Re: Hashing, history and killers

Author: Robert Hyatt

Date: 08:09:07 11/12/00

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On November 12, 2000 at 09:12:39, Alvaro Jose Povoa Cardoso wrote:

>Could someone please explain where exactly we update the hash table, the history
>table and the killers?

history/killers:  whenever the search at a particular ply finishes with
score > alpha.

hash:  whenever the search at a particular ply finishes, no matter what
it returns as the final value.


>
>I have seen several chess program sources, and in some the update is done only
>when Score>Alpha (a better move is found).
>Others, like Crafty, update when Score>Alpha_and_Score>=Beta, in other words,
>when a fail high occurs.

Crafty doesn't do that.  It updates killers/history when the score is > alpha.
You missed the _second_ call to History() near the bottom of search,
where the test is "is current value different than original alpha value?"



>I'm cunfused.
>What is the difference, between updating only when Score>Alpha and updating when
>Score>=Beta (fail high) ?
>
>Thank you
>
>Alvaro Cardoso



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