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Subject: Re: Hash in Crafty

Author: Tom Kerrigan

Date: 15:59:13 05/31/00

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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



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