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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-68) Bloom filters have much higher false-positive rate than expected
Date Fri, 10 Apr 2009 02:25:13 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-68?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12697714#action_12697714
] 

Jonathan Ellis commented on CASSANDRA-68:
-----------------------------------------

Made words test optional.

Also split 0004 changes into tests and code, but I don't think that's going to be too useful.
 If you want to test the old hash functions the easiest thing is probably to modify Filter.getHashBuckets
to use the old hash functions instead.

But I remember that you will see from 50% to 200% more FP than you should.  Sorry I don't
have the code anymore.  (Lost in a git rebase, apparently.)

> Bloom filters have much higher false-positive rate than expected
> ----------------------------------------------------------------
>
>                 Key: CASSANDRA-68
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-68
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>         Attachments: 0001-r-m-unused-code-including-entire-CountingBloomFilte.patch,
0002-replace-JenkinsHash-w-MurmurHash.-its-hash-distrib.patch, 0003-rename-BloomFilter.fill-add.patch,
0004-rewrite-bloom-filters-to-use-murmur-hash-and-combina.patch, 0004a-tests.patch, 0004b-code.patch
>
>
> Gory details: http://spyced.blogspot.com/2009/01/all-you-ever-wanted-to-know-about.html

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