Author: Russell Reagan
Date: 12:02:24 02/04/04
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On February 04, 2004 at 14:35:10, Dann Corbit wrote: >On February 04, 2004 at 14:01:06, Reinhard Scharnagl wrote: > >>Is there anything known as "inverted bitboard" or "reversed bitboard"? >> >>It would be good to know, because this could be a name for some parts of my >>approach. > >Yes. A fellow had a web page a while back and thought that his reversed >bitboards would make the fastest engine in the world. > >Actually, reading his page showed some interesting ideas, but I don't think he >ever got his chess engine off the ground. > >It was perhaps 2 years ago. I can see how to make it work, at a nontrivial cost (of course) ;-) As far as I can tell, you have to keep track of eight reversed bitboards, and then you can get fast attack generation using the x^(x-2) bit propogation trick with no table lookups. In isolation, x^(x-2) seems very fast, but updating eight reversed bitboards (as opposed to three rotated) seems like you might break even at best. Maybe it would work on a 64-bit machine that can execute many instructions per cycle. That might be fast enough since updating each bitboard can be independently done, and thus can be done in parallel.
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