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https://issues.apache.org/jira/browse/MAHOUT-953?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13404611#comment-13404611
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Stuart Smith commented on MAHOUT-953:
-------------------------------------
Yup, let me take a look at this when I look into another bug I have (since I
should be re-syncing & re-duplicating for both anyways). Thanks for checking
these out!
> ArffVectorIterable does not gracefully handle duplicate attribute name
> ----------------------------------------------------------------------
>
> Key: MAHOUT-953
> URL: https://issues.apache.org/jira/browse/MAHOUT-953
> Project: Mahout
> Issue Type: Improvement
> Components: Integration
> Affects Versions: 0.6
> Reporter: Stuart Smith
> Priority: Trivial
>
> If you have duplicate attribute names in your ARFF file, and you have
> non-sparse arff vectors, ARFFVectorIterable.computeNext will throw a
> ArrayIndexOutOfBoundsExceptions, as it allocates a DenseVector with the size
> of your attribute labels (duplicates removed), but your arff vectors could
> have more values (if they reference the attribute at both indexes). This is a
> somewhat pathological ARFF file.
> Not sure if I should note the error (throw an exception) in computeNext()
> when it's out of bounds, or when someone tries to add duplicate label to the
> MapBackedArffModel.
> My first impulse would be to check in computeNext(), but addLabel() in
> MapBackedArffModel will do something rather pathological in the case of
> duplicate attributes: it overwrites the Label map with the new index, but the
> idxLabel map will hold a mapping from both indexes to the attribute name, so
> it's out of sync.. so it may be best to disallow duplicate attribute names
> "IllegalArgumentException" altogether.
> For example
> @attribute my_attribute NUMERIC
> @attribute my_attribute NUMERIC
> addLabel()
> addLabel()
> labelBindings -> ('my_attribute', 1)
> idxLabel -> (0, 'my_attribute), (1, 'my_attribute')
> I'll happily submit a patch, just wondering if it should be in computeNext()
> or addLabel()
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