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Subject: Re: 64 bit 90 degree rotations -- a summary from USENET

Author: Dann Corbit

Date: 12:39:01 06/11/02

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On June 11, 2002 at 15:27:27, Gian-Carlo Pascutto wrote:

>On June 11, 2002 at 14:28:24, Dann Corbit wrote:
>
>>True enough.  But I have a notion for that which I have not tried yet.  The
>>table of bytes idea works for those.  You just grab the 8 bytes from the
>>original bitboard and by a table lookup, put them in the target slot in a single
>>operation.  I am also going to try a union with unsigned char to see if it is
>>faster than shifting.
>
>If you figure out the fastest method on x86 for each rotation
>(and the reversed bitboard), can you send me a mail?

I'll probably post it here.  Another interesting notion is the reversed (mirror)
bitboard.  This was a guy going on about it some time ago:
http://www.fys.ku.dk/~fischer/Temp/New%20Technology.htm
and I found a good way to reverse it in a hurry.  I don't know if it is any good
for actual chess calculations, but it makes some interesting food for thought.



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