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Subject: Re: Hash in Crafty

Author: Dave Gomboc

Date: 15:22:13 06/01/00

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On May 31, 2000 at 18:59:13, Tom Kerrigan wrote:

>On May 31, 2000 at 18:28:43, Brian Richardson wrote:
>
>>On May 31, 2000 at 17:45:27, Bas Hamstra wrote:
>>
>>>What is the philosophy behind Crafty's hashcode? I see a couple of things that
>>>make me wonder:
>>>
>>>- Black hashvalue is NOT-ted
>>>- 2 separate hashtables, one depth-preferred, one always-replace
>>>
>>>Is this fundamentally better than my method:
>>>
>>>- Table[Size][BucketSize] where BucketSize = 8
>>>- With a "store" simply replace the worst depth of the 8 entries (is there is
>>>none empty) regardless of movecolor
>>>- A bit in the hashrecord indicates movecolor
>>>
>>>Note that a "retrieve" has to read 8 hashrecords worst case. It doesn't seem to
>>>slow me down much. I don't store D=0 nodes or qnodes.
>>>
>>>Comments are appreciated.
>>>
>>>
>>>Regards,
>>>Bas.
>>
>>Allow me to comment on Crafty (subject to correction/amplification by Bob Hyatt,
>>of course).  I have looked at Crafty's hash code quite a bit.
>>
>>The NOT for black skips the need for separate black/white hash tables or the
>>need to double XOR the side to move (once to back out the old side and once
>>again to update the new side), since the side to move is a part of the
>
>I just have one value, black_to_move.
>-Tom

I guess so does Bob, and it is 0xFFFFFFFF. ;-)

Dave



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