linux-kernel - Re: [RFC] div64

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Message-ID: <20070306120433.3863e6c9@freekitty>
Date:	Tue, 6 Mar 2007 12:04:33 -0800
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Roland Kuhn <rkuhn@....physik.tu-muenchen.de>,
	Andi Kleen <andi@...stfloor.org>,
	Eric Dumazet <dada1@...mosbay.com>,
	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC] div64_64 support

On Tue, 6 Mar 2007 20:48:41 +0100
Andi Kleen <andi@...stfloor.org> wrote:

> On Tue, Mar 06, 2007 at 10:29:41AM -0800, Stephen Hemminger wrote:
> > Don't count the existing Newton-Raphson out. It turns out that to get enough
> > precision for 32 bits, only 4 iterations are needed. By unrolling those, it
> > gets much better timing.
> 
> But did you fix the >2^43 bug too?

It was caused by not doing x^2 in 64 bit.

> 
> SGI has already shipped 10TB Altixen, so it's not entirely theoretical.
> 
> -Andi
> 


-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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