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Subject: Re: regular hash key & pawn hash key together--good idea?

Author: Andrew Dados

Date: 17:36:36 09/16/99

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On September 16, 1999 at 20:24:45, Robert Hyatt wrote:

>On September 16, 1999 at 12:38:41, Andrew Dados wrote:
>
>>On September 16, 1999 at 12:19:24, Tom Kerrigan wrote:
>>
>>>The overhead of separating 24 bits is trivial:
>>>
>>>(hash_key >> 40)
>>>
>>>-Tom
>>
>> Well.. you have to detect pawn moves/captures exactly as in 'normal, 2-key
>>way', separate that, xor, mask topmost bits and finally combine back. No real
>>gain when you think of that. (otherwise xor would screw both 'parts' of key).
>>But that of course only for xor way...
>> -Andrew-
>
>
>You probably wouldn't have to do this...  you would just put bits in the right
>part of each of the random numbers you xor in/out.  IE pawns only have bits on
>the right end, pieces only on the left.. then you would ignore which is which.

 If I did that, I would end up with a pawn signature dependant on what pieces
was moved and where...  because even xoring with all zeroes would change pawn
signature part bits (talking 24 pawn bits here).

>
>However, on a PC, if I did this, I would just do two 32 bit values separately
>to avoid the overhead...

 That's only way to make this efficiency idea efficient, imo (or 64/32 separate
signatures, but then 96 bit divide (or modulo) operation is needed - so I'll
wait for merced with that :)



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