linux-kernel - Re: [RFC] div64

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Message-ID: <Pine.LNX.4.61.0702270103060.23355@yvahk01.tjqt.qr>
Date:	Tue, 27 Feb 2007 01:05:26 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC] div64_64 support


On Feb 26 2007 15:44, Stephen Hemminger wrote:
>> >-		x = (2 * x + (uint32_t) div64_64(a, x*x)) / 3;
>> >+		x = (2 * x + (u32) (a / x*x)) / 3;
>> 
>> Previously there was div64_64(a, x*x) which is equivalent to
>> (a)/(x*x), or just: a/(x^2). But now you do a/x*x, which is
>> equivalent to a*x/x (in the domain of real numbers). Furthermore,
>> a/x*x is a-(a%x), which does not even remotely match a/(x^2).
>> 
>Been there, done that, don't want to repeat it...

I am sorry I don't quite follow.


Jan
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