From: Stephen Hemminger <shemminger@linux-foundation.org>
To: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [RFC] div64_64 support
Date: Mon, 26 Feb 2007 16:07:08 -0800 [thread overview]
Message-ID: <20070226160708.3c7a8d29@freekitty> (raw)
In-Reply-To: <Pine.LNX.4.61.0702270103060.23355@yvahk01.tjqt.qr>
On Tue, 27 Feb 2007 01:05:26 +0100 (MET)
Jan Engelhardt <jengelh@linux01.gwdg.de> 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...
--
Stephen Hemminger <shemminger@linux-foundation.org>
next prev parent reply other threads:[~2007-02-27 0:08 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-24 1:05 [RFC] div64_64 support Stephen Hemminger
2007-02-24 16:19 ` Sami Farin
2007-02-26 19:28 ` Stephen Hemminger
2007-02-26 19:39 ` David Miller
2007-02-26 20:09 ` Jan Engelhardt
2007-02-26 21:28 ` Stephen Hemminger
2007-02-27 1:20 ` H. Peter Anvin
2007-02-27 3:45 ` Segher Boessenkool
2007-02-26 22:31 ` Stephen Hemminger
2007-02-26 23:02 ` Jan Engelhardt
2007-02-26 23:44 ` Stephen Hemminger
2007-02-27 0:05 ` Jan Engelhardt
2007-02-27 0:07 ` Stephen Hemminger [this message]
2007-02-27 0:14 ` Jan Engelhardt
2007-02-27 6:21 ` Dan Williams
2007-03-03 2:31 ` Andi Kleen
2007-03-05 23:57 ` Stephen Hemminger
2007-03-06 0:25 ` David Miller
2007-03-06 13:36 ` Andi Kleen
2007-03-06 14:04 ` [RFC] div64_64 support II Andi Kleen
2007-03-06 17:43 ` Dagfinn Ilmari Mannsåker
2007-03-06 18:25 ` David Miller
2007-03-06 18:48 ` H. Peter Anvin
2007-03-06 13:34 ` [RFC] div64_64 support Andi Kleen
2007-03-06 14:19 ` Eric Dumazet
2007-03-06 14:45 ` Andi Kleen
2007-03-06 15:10 ` Roland Kuhn
2007-03-06 18:29 ` Stephen Hemminger
2007-03-06 19:48 ` Andi Kleen
2007-03-06 20:04 ` Stephen Hemminger
2007-03-06 21:53 ` Sami Farin
2007-03-06 22:24 ` Sami Farin
2007-03-07 0:00 ` Stephen Hemminger
2007-03-07 0:05 ` David Miller
2007-03-07 0:05 ` Sami Farin
2007-03-07 16:11 ` Chuck Ebbert
2007-03-07 18:32 ` Sami Farin
2007-03-08 18:23 ` asm volatile [Was: [RFC] div64_64 support] Sami Farin
2007-03-08 22:01 ` asm volatile David Miller
2007-03-06 21:58 ` [RFC] div64_64 support David Miller
2007-03-06 22:47 ` [PATCH] tcp_cubic: faster cube root Stephen Hemminger
2007-03-06 22:58 ` cube root benchmark code Stephen Hemminger
2007-03-07 6:08 ` Update to " Willy Tarreau
2007-03-08 1:07 ` [PATCH] tcp_cubic: use 32 bit math Stephen Hemminger
2007-03-08 2:55 ` David Miller
2007-03-08 3:10 ` Stephen Hemminger
2007-03-08 3:51 ` David Miller
2007-03-10 11:48 ` Willy Tarreau
2007-03-12 21:11 ` Stephen Hemminger
2007-03-13 20:50 ` Willy Tarreau
2007-03-21 18:54 ` Stephen Hemminger
2007-03-21 19:15 ` Willy Tarreau
2007-03-21 19:58 ` Stephen Hemminger
2007-03-21 20:15 ` [PATCH 1/2] div64_64 optimization Stephen Hemminger
2007-03-21 20:17 ` [PATCH 2/2] tcp: cubic optimization Stephen Hemminger
2007-03-22 19:11 ` David Miller
2007-03-22 19:11 ` [PATCH 1/2] div64_64 optimization David Miller
2007-03-08 4:16 ` [PATCH] tcp_cubic: use 32 bit math Willy Tarreau
2007-03-07 4:20 ` [PATCH] tcp_cubic: faster cube root David Miller
2007-03-07 12:12 ` Andi Kleen
2007-03-07 19:33 ` David Miller
2007-03-06 18:50 ` [RFC] div64_64 support H. Peter Anvin
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