netdev - Re: [RFC] div64

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Message-ID: <Pine.LNX.4.61.0702270111200.23355@yvahk01.tjqt.qr>
Date:	Tue, 27 Feb 2007 01:14:00 +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 16:07, Stephen Hemminger wrote:
>> 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.
>
>Once before a missed paren's caused a TCP congestion window bug that
>took 6 months before it was found...

Hah, just as I expected.

|On Tue, 27 Feb 2007 00:02:50 +0100 (MET), Jan Engelhardt wrote:
|>Then our reviewers should catch it, and if not, the janitors will.


Jan
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