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Subject: Re: When to RecordHash()?

Author: Sune Fischer

Date: 01:52:35 12/26/01

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On December 25, 2001 at 23:56:56, Robert Hyatt wrote:

>On December 25, 2001 at 20:21:49, Sune Fischer wrote:
>
>>I'm sitting here with an implementation problem, I can think of a few ways to
>>solve it, but perhaps there is an even better one.
>>
>>The problem is I can't always get the best move in a position when searching, I
>>need a beta cutoff or an improvement in the alpha value. So it isn't save for me
>>to assume there is killer in all recorded hash entries, and if I only
>>recordhash() when I _can_ put a killer in, then I miss out on some scores.
>>
>>So I was wondering what solution you guys have found?
>>
>>-S.
>
>
>If I understand your question, there are three kinds of positions where you
>can store a hash entry.  PV entry where the score is _EXACT_.  You should
>have a best move to store hre.
>
>LOWER entry which is AKA a fail-high position.  A move caused this fail high
>and it should be stored in the hash as best.
>
>UPPER entry which is AKA a fail-low position.  There is _no_ best move in this
>position.  I simply store a 0 for such cases...

Yeah that's what I mean, the first thing i do in the AB search (I'm not using
PVS yet) is to probe, and if succesful I put the killer into the pv and return
with the score.
At the end of the search I expect there to be a move in the pv, namely the best
move the search could find. What if the entire search is returned from a probe
hit, one that did not have a move stored, then the pv is empty!
I hasn't happend to me yet because most entries do have a killer, but it could
happen I guess.

-S.



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