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Subject: Re: Hash Table/Best Move

Author: Robert Hyatt

Date: 10:09:32 07/30/03

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On July 29, 2003 at 03:44:42, Rick Bischoff wrote:

>Hi all,
>
>I am getting the following statistic from my program:
>
><pre>
> 0/18      0  1426407 Ke6 h3 Kd5 Rg2 Kc5 h4 Kb5 h5 Ka5 h6 Ka6
>move found: 85570 not found: 118
></pre>
>
>Which means of the 88570 times the hashtable didn't have a good value, it still
>had a  good move to try first; the other 118 times it didnt have a good value,
>it had an illegal move... Is this the kind of percentage you all see in your
>engines?


I don't like the "illegal move" issue.  How can you possibly store an illegal
move in the hash table?

You have a good move to store if you back up a score that is > alpha, which
might mean you are backing up a PV, or a fail-high.  You don't have a good
move if you are backing up alpha, because _every_ move failed low and there is
no way to know which is best...

But storing an illegal move is something that should not happen.  If you back
up alpha, set the hash move to zero.



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