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From: dbrooks@osf.osf.org (David Brooks)
Newsgroups: comp.lang.c
Subject: Re: count of bits set in a long
Keywords: bits set, count of, long
Message-ID: <13772@paperboy.OSF.ORG>
Date: 25 Sep 90 02:44:39 GMT
References: <37545@ut-emx.uucp>
Sender: news@OSF.ORG
Reply-To: dbrooks@osf.org (David Brooks)
Organization: Open Software Foundation
Lines: 19

In article <37545@ut-emx.uucp> nwagner@ut-emx.uucp (Neal R. Wagner) writes:
>
>  I need a fast method to count the number of bits that are set in a 32-bit
>integer on a Sun 3/80 running 4.0.3 SunOS.

I wish people who aren't using the net to do their homework, but look
as though they are, would say so.

>Is there a faster way in C?  How close in speed to a hand-coded assembly
>routine would a fast method in C be (after the latter is run through the
>optimizer)?

Well, if you don't restrict youself to the Sun3, I once knew a machine
that could do it in one instruction.  I doubt if any compiler could
compile your code into that.
-- 
David Brooks				dbrooks@osf.org
Systems Engineering, OSF		uunet!osf.org!dbrooks
"A Loaf of Bread, a Jug of Wine, and Six Spades Redoubled -- Omar somebody.