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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-875) Use MurmurHash instead of JenkinsHash
Date Mon, 22 Sep 2008 17:40:44 GMT

    [ https://issues.apache.org/jira/browse/HBASE-875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12633391#action_12633391
] 

stack commented on HBASE-875:
-----------------------------

Thanks for the patch Andrzej.  It looks great.  One comment. In  src/java/org/onelab/filter/Filter.java,
you add in versioning.  Deserializing, if first int is > 0, then you assume Filter is of
an older version.  Is this test safe?  Its not possible for a hash to be negative?

Otherwise, the configuration of which hash to use applies to BloomFilters only it seems? 
If so, that seems right; it shouldn''t break hbase finding encoded region names in the filesystem.


> Use MurmurHash instead of JenkinsHash
> -------------------------------------
>
>                 Key: HBASE-875
>                 URL: https://issues.apache.org/jira/browse/HBASE-875
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: util
>    Affects Versions: 0.19.0
>            Reporter: Andrzej Bialecki 
>         Attachments: murmur.patch
>
>
> I recently ported the MurmurHash (http://murmurhash.googlepages.com/) to Java, and according
to my tests it's roughly 5 times faster than the current version of JenkinsHash in the trunk/
. According to the author (and other analysts at comp.sci.crypt) this hash has an excellent
avalanche behavior, and low collision rate. I propose to either replace the JenkinsHash or
add this hash as an option to be used in BloomFilter-s and related classes.
> If your opinion is positive, I'll prepare a patch. The Java implementation of the hash
can be found here: http://www.getopt.org/murmur/MurmurHash.java

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