Author: Robert Hyatt
Date: 15:06:30 01/20/03
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On January 20, 2003 at 15:59:52, Matt Taylor wrote: >On January 20, 2003 at 14:06:15, Uri Blass wrote: > >>I find in crafty 2 functions for firstone >> >>The first function is something has some function cntlzw that I am unable to >>understand. > >The cntlzw is an intrinsic for "count leading zeros in a word." Since Dr. Hyatt >orders his bitboards in reverse (i.e. MSB = bit 0, LSB = bit 63), the count >leading zeros will give him the index. > I did this because Cray has always had the _same_ instruction. leadz for count leading zeros. :) >As far as I can tell, the least significant bit is the easiest to pull out. I've >still got my optimized "bit scan & reset" algorithms that work for LSB = bit 0 >and MSB = bit 63. I'm working on one last variant, but I think the winner is >already clear. Per request, I will be posting results here soon. > >-Matt
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