From: wli@movementarian.org
To: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
netfilter-devel@vger.kernel.org,
Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH] Update jhash.h with the new version of Jenkins' hash
Date: Wed, 11 Feb 2009 19:12:23 -0500 [thread overview]
Message-ID: <20090212001223.GA5757@movementarian.org> (raw)
In-Reply-To: <alpine.DEB.2.00.0902111107480.15665@blackhole.kfki.hu>
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
The golden ratio is not an arbitrary value, nor is it a food ration.
It is (sqrt(5)+1)/2. and the original value of JHASH_GOLDEN_RATIO
approximated its reciprocal and/or fractional part in fixed point.
(double)0xdeadbeef/((unsigned long long)1 << 32) is a rather poor
approximation of (sqrt(5)-1)/2. If this value which is not the
golden ratio is arbitrary, calling it something different from
JHASH_GOLDEN_RATIO would surprise the code's readers much less.
-- wli
next prev parent reply other threads:[~2009-02-12 0:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-11 10:19 [PATCH] Update jhash.h with the new version of Jenkins' hash Jozsef Kadlecsik
2009-02-11 20:19 ` Michał Mirosław
2009-02-11 22:50 ` Jozsef Kadlecsik
2009-02-11 23:23 ` Michał Mirosław
2009-02-12 0:12 ` wli [this message]
2009-02-12 0:29 ` David Miller
2009-02-12 0:41 ` Jan Engelhardt
2009-02-12 9:05 ` Jarek Poplawski
2009-02-12 9:55 ` Jarek Poplawski
2009-02-12 9:11 ` Jozsef Kadlecsik
2009-02-12 9:16 ` Patrick McHardy
2009-02-12 9:41 ` Jozsef Kadlecsik
2009-02-12 13:46 ` Kyle Moffett
2009-02-17 17:13 ` Jozsef Kadlecsik
2009-02-18 5:11 ` Rusty Russell
2009-02-18 11:50 ` Ilpo Järvinen
2009-02-12 19:58 ` Eric W. Biederman
2009-02-12 2:58 ` Rusty Russell
-- strict thread matches above, loose matches on Subject: below --
2009-02-10 19:40 Jozsef Kadlecsik
2009-02-10 21:19 ` Scott Feldman
2009-02-10 22:03 ` Jozsef Kadlecsik
2009-02-11 1:17 ` David Miller
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