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Re: [RFC] enhanced version of net_random()

To: root@xxxxxxxxxxxxxxxxxx
Subject: Re: [RFC] enhanced version of net_random()
From: "David S. Miller" <davem@xxxxxxxxxx>
Date: Fri, 20 Aug 2004 12:48:23 -0700
Cc: adilger@xxxxxxxxxxxxx, jlcooke@xxxxxxxxxxxxxx, shemminger@xxxxxxxx, alan@xxxxxxxxxxxxxxxxxxx, tytso@xxxxxxx, netdev@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <Pine.LNX.4.53.0408201518250.25319@chaos>
References: <20040812104835.3b179f5a@xxxxxxxxxxxxxxxxxxxxx> <20040820175952.GI5806@xxxxxxxxxxxxxx> <20040820185956.GV8967@xxxxxxxxxxxxxxxxxxxx> <Pine.LNX.4.53.0408201518250.25319@chaos>
Sender: netdev-bounce@xxxxxxxxxxx
On Fri, 20 Aug 2004 15:22:09 -0400 (EDT)
"Richard B. Johnson" <root@xxxxxxxxxxxxxxxxxx> wrote:

> The attached code will certainly work on Intel machines. It is
> in the public domain, having been modified by myself to produce
> a very long sequence...

How long a period does it have?  The one we're adding to the
networking has one which is 2^88.

> I wouldn't suggest converting it to 'C' because the rotation
> takes many CPU instructions when one tries to do the test, shift,
> and OR in 'C',

You only need 2 'shifts' and an 'or' to do a rotate in C.
No tests are needed.

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