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Message-ID: <20090211232335.GA16996@rere.qmqm.pl>
Date: Thu, 12 Feb 2009 00:23:35 +0100
From: Michał Mirosław <mirq-linux@...e.qmqm.pl>
To: Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org,
Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH] Update jhash.h with the new version of Jenkins' hash
On Wed, Feb 11, 2009 at 11:50:38PM +0100, Jozsef Kadlecsik wrote:
> On Wed, 11 Feb 2009, Micha? Miros?aw wrote:
> > On Wed, Feb 11, 2009 at 11:19:20AM +0100, Jozsef Kadlecsik wrote:
> > > /* The golden ration: an arbitrary value */
> > > -#define JHASH_GOLDEN_RATIO 0x9e3779b9
> > > +#define JHASH_GOLDEN_RATIO 0xdeadbeef
> > I have a stupid question: if this is arbitrary value, then why not
> > just get rid of it (IOW use zero as it's used in addition)?
> lookup3() is a quite generic hash function and it supports 0-byte strings
> as input keys too. If the input key is a 0-byte string and the arbitrary
> value is zero, then the hash value simply equal to the initval. In order
> to avoid that case, the arbitrary value must be nonzero.
Double-hashing, of course! I really need more sleep. Sorry for the noise. :>
Best Regards,
Michał Mirosław
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