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Subject: Re: Hash move question

Author: Robert Hyatt

Date: 18:32:57 06/25/04

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On June 25, 2004 at 06:12:45, Jeff GAZET wrote:

>Hi,
>
>in the search function, when i've got a corresponding hash entry for the current
>position, i look as the hash move. And this move is not valid for the current
>position (i.e. there is no piece on the from square), how is it possible as
>current hash and the hash in the table are the same ?


You have a bug.  One of the following is happening most likely:

(1) your hash signature is wrong.  As you incrementally update it, you are
wrecking it.  This can be detected by simply re-computing the hash after the
incremental update to see if you get the _same_ thing.  If not, fix it.

(2) you are not using a 64 bit hash signature.  32 bits is not enough and you
can expect _lots_ of this kind of problem.  Go to 64 bit random numbers and
signature.

(3) you are storing a bogus move inside the search.  IE when you store a "UPPER"
bound position, you have _no_ best move to store.  Be sure you store zero rather
than garbage.  This is a likely candidate.




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