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Subject: Hash kollision ??

Author: Andreas Herrmann

Date: 05:28:33 02/13/01

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On February 13, 2001 at 07:37:41, Gian-Carlo Pascutto wrote:

>On February 13, 2001 at 07:25:52, Andreas Herrmann wrote:
>
>>>It depends on whether you apply the extensions before probing into
>>>the hashtable or not.
>>>
>>
>>Means this, i can use both ways?
>
>As long as you keep things consistent. Same position at same
>point in tree should be same hit in hash.
>
>>If i extend before the hash probe, i have to store depth as depth+extension?
>
>Indeed.
>
>--
>GCP


Is one of the above ways better than the other (depth with or without
extension)?


Thanks for your answers. I ask this because i have a bug if i use upper and
exact bounds. Sometimes my chess program spends the opponent a piece (a queen, a
rook or so) for nothing.
From the above ways i tryd in the past very often both ways, but the bug was in
both cases. I think i have to look to other reasons for that?

I often ask me, could this be a hash kollision? But i think not, because this
happens in about 1 of 3 games. I only uses 32-bit hash keys because Delphi
cannot manage XOR with 64-bit values. But i think many other chess programs uses
only 32-bit hash keys and have not such a bug. If i play the same position in
what this happens i never got the wrong move in the pv. So i cannot reproduce
the error.


Andreas




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