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https://issues.apache.org/jira/browse/MAHOUT-890?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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tom pierce updated MAHOUT-890:
------------------------------
Attachment: MAHOUT-890-2.patch
This patch (MAHOUT-890-2) adds the new implementation (under fpgrowth2)
alongside the old with a minimal number of boxed primitives in the parallel
version. This patch depends on MAHOUT-920, MAHOUT-921 and MAHOUT-927.
Tests are included that check the new implementation against known-good output
and the existing implementation.
The sequential implementation does not have a post-filter to create the
complete per-item itemsets (though all the same itemsets are found - the new
implementation returns de-duped sets). Otherwise the results should be
interchangeable.
> 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: MAHOUT-890-2.patch, MAHOUT-890.patch, addSynth.patch,
> logtrees.patch, simpleFPG.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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