[jira] [Comment Edited] (MAHOUT-1180) Multinomial throws ConcurrentModificationException when iterating and setting probabilities

["Dan Filimon (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAHOUT-1180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13626484#comment-13626484 ] 

Dan Filimon edited comment on MAHOUT-1180 at 4/9/13 11:11 AM:
--------------------------------------------------------------

Fixed indentation and added a relevant tests.
                
      was (Author: dfilimon):
    Updated and added a relevant tests.
                  
> Multinomial<T> throws ConcurrentModificationException when iterating and setting probabilities
> ----------------------------------------------------------------------------------------------
>
>                 Key: MAHOUT-1180
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-1180
>             Project: Mahout
>          Issue Type: Bug
>    Affects Versions: 0.8
>            Reporter: Dan Filimon
>            Priority: Minor
>         Attachments: MAHOUT_1180.patch, MAHOUT_1180.patch
>
>
> Here's [1] an example of the problem (from BallKMeans, lines 225-232, [2]).
> When iterating through the elements in a Multinomial and updating the probabilities, sometimes newWeight becomes 0 (because of using CosineDistances).
> When setting a weight to 0 in Multinomial, the element is removed from the items hash map while using the hash map for iteration.
> This causes a ConcurrentModificationException.
> [1] https://gist.github.com/dfilimon/5270234
> [2] https://github.com/dfilimon/mahout/blob/skm/core/src/main/java/org/apache/mahout/clustering/streaming/cluster/BallKMeans.java#L225

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