Message-ID: <37B4D8BC.6465@ns.sympatico.ca>
From: Klaas <klaas AT ns DOT sympatico DOT ca>
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Newsgroups: comp.os.msdos.djgpp
Subject: Re: Bit counting?
References: <37B45836 DOT EAD7C82D AT swipnet DOT se> <37B48ABE DOT 110D2C13 AT intel DOT com>
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Date: Fri, 13 Aug 1999 23:47:24 -0300
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To: djgpp AT delorie DOT com
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Kurt Alstrup wrote:
> 
> Try this little function, I guess it may gain if written in assembly
> though ..
> 
> /*
>  *      Ones
>  *
>  * This magic counts the number of bits in one longword
>  */
> 
> int
> Ones(unsigned long mask)
> {
>   register unsigned long y;
> 
>   y = (mask >> 1) & 033333333333;
>   y = mask - y - ((y >>1) & 033333333333);
>   return (int) (((y + (y >> 3)) & 030707070707) % 077);
> }
> 
> Regards,
> Kurt Alstrup

Doesn't the modulo make it rather slow?

-Mike