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From "Dawid Weiss (Commented) (JIRA)" <>
Subject [jira] [Commented] (MAHOUT-862) MurmurHash 3.0
Date Wed, 02 Nov 2011 16:31:33 GMT


Dawid Weiss commented on MAHOUT-862:

Are speed gains on bytebuffers a result of unsafe underlying buffer accesses? A simple array
loop with predictable ends should be optimized pretty much the same way though (boundary checks
only, followed by no-checks accesses); wonder where the gain comes from then?

Also, this could be rewritten to actually make use of Unsafe if it's available -- I bet with
larger memory chunks the speed gain would be noticeable.
> MurmurHash 3.0
> --------------
>                 Key: MAHOUT-862
>                 URL:
>             Project: Mahout
>          Issue Type: Improvement
>            Reporter: Grant Ingersoll
>            Assignee: Grant Ingersoll
>            Priority: Minor
>         Attachments: MAHOUT-862.patch
> Yonik has ported an implementation of MurmurHash 3.0 and put it in the public domain:
> It's a port of which says: 
> {quote}
> (I reserve the right to tweak the constants after people have had a chance to bang on
it). Murmur3 has better performance than MurmurHash2, no repetition flaw, comes in 32/64/128-bit
versions for both x86 and x64 platforms, and the 128-bit x64 version is blazing fast - over
5 gigabytes per second on my 3 gigahertz Core 2.
> In addition, the library of test code that I use to test MurmurHash (called SMHasher)
has been released - it's still rough (and will only compile under VC++ at the moment), but
it contains everything needed to verify hash functions of arbitrary output bit-lengths.
> Murmur3 and all future versions will be hosted on Google Code here -
- you can access the codebase via the 'Source' tab at the top.
> {quote}
> See also
> We should add support for it and hook into MinHash

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