Author: Bas Hamstra
Date: 07:57:15 02/10/04
Go up one level in this thread
On February 09, 2004 at 09:07:41, Gerd Isenberg wrote:
>On February 09, 2004 at 05:09:07, Renze Steenhuisen wrote:
>
>>
>>Hi there!
>>
>>does anyone know the fastest way to determine the lcoation of the Least/Most
>>Significant Bit, and to clear that bit?
>>
>>In my case the most important platforms (at the moment) are Pentium III and IV.
>>
>>Thanks!
>
>find lsb from CCC archives:
>
>http://chessprogramming.org/cccsearch/ccc.php?art_id=265616
>
>Walter Faxon's magic BitScan:
>http://chessprogramming.org/cccsearch/ccc.php?art_id=272378
>
>Matt Taylor's De Bruijn folding trick:
>http://chessprogramming.org/cccsearch/ccc.php?art_id=305965
>
>Gerd
>
>
>>
>>Renze
Gerd,
IMO the BSF instruction is still fastest. Don't test this in loops, in a
searching engine you get quite different results and BSF is in my case clearly
the winner, especially for the paltforms he mentiones, and besides he is not
talking 64 bit...
Bas.
int LastOne(unsigned int Number)
{ asm mov EAX, Number
asm BSF EAX, EAX
}
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