[infinispan-dev] MurmurHash fixes

[Manik Surtani]

I don't have a problem with including libraries in principle, but it really needs to be worth it.  In this case, there is no point dragging in a whole bunch of Hadoop stuff for a single class implementation of a hash function.  :-)

On 14 Jan 2011, at 03:20, david marion wrote:

> Manik,
>  
>   Being new here, I'm not totally sure of JBoss' stance on including other libraries. Hadoop has a Murmur2 hash implementation that I have been using at work for a while with no problems. Just a thought.
>  
> -- Dave Marion
> 
>  
> > From: manik at jboss.org
> > Date: Thu, 13 Jan 2011 19:35:44 +0000
> > To: infinispan-dev at lists.jboss.org
> > Subject: [infinispan-dev] MurmurHash fixes
> > 
> > Guys,
> > 
> > The MurmurHash2 impl we have in 4.2.0 is buggy in that my translation from the original C source was faulty and it effectively hashes over just 31 bits instead of 32. It means the distribution result isn't as good as it could be.
> > 
> > Now it isn't that easy for me to just *fix* this in 4.2.1, since it means keys mapped to nodes using 4.2.0 may not map to the same node in 4.2.1.
> > 
> > So here is what I propose:
> > 
> > 1) Fix it in 4.2.x as MurmurHash2A
> > 2) Use MurmurHash2A by default, *unless* a config flag is provided that forces the use of MurmurHash2. (e.g., <hash function="MurmurHash2">)
> > 
> > This will even give us the ability to use MurmurHash3 in 5.0 when we have it.
> > 
> > WDYT?
> > 
> > Cheers
> > Manik
> > --
> > Manik Surtani
> > manik at jboss.org
> > twitter.com/maniksurtani
> > 
> > Lead, Infinispan
> > http://www.infinispan.org
> > 
> > 
> > 
> > 
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--
Manik Surtani
manik at jboss.org
twitter.com/maniksurtani

Lead, Infinispan
http://www.infinispan.org



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