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From "Sean Owen (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAHOUT-890) Performance issue in FPGrowth
Date Sun, 20 Nov 2011 12:17:51 GMT

    [ https://issues.apache.org/jira/browse/MAHOUT-890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13153770#comment-13153770
] 

Sean Owen commented on MAHOUT-890:
----------------------------------

Do you have a suggested fix, or is it more of an observation? I didn't see a change in the
patches.
                
> Performance issue in FPGrowth
> -----------------------------
>
>                 Key: MAHOUT-890
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-890
>             Project: Mahout
>          Issue Type: Bug
>          Components: Frequent Itemset/Association Rule Mining
>    Affects Versions: 0.6
>            Reporter: tom pierce
>         Attachments: addSynth.patch, logtrees.patch, smallexample.dat
>
>
> I've encountered a dataset which indicates there is probably a performance bug lurking
in the FPGrowth implementation.  This set may be a bit of an unusual target for FPG - there's
a relatively modest number itemsets, and many items with a Zipfy distribution.  I am attaching
a patch (addSynth.patch) to add a similar dataset as core/src/test/resources/FPGsynth.dat.
> FPGsynth.dat can take minutes or a few hours to process, depending on how it is grouped
out to machines.  If run in sequential mode, or with "-g 50" it will take considerable time.
 Most reducers/"anchor items" are processed quickly, but a small number take a handful of
minutes, and one or two take a long time.  If you experiment with this data, I suggest using
 '-s 50 -regex "[ ]+"'. 
> Digging into this, I've found that the tree pruning code sometimes creates surprising
trees.  One oddity I've observed is 0-count nodes, sometimes with non-zero children.  The
other is that sometimes subtrees seem to get repeated.  I'm attaching a sample input file
(smallexample.dat, use the whitespace regex with this one, too) and a patch which adds some
logging in pruneFPTree and growthBottomUp which will print out some interesting trees when
run with the smallexample.dat input.

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