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From "Martin Illecker (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HAMA-834) Fix KMeans example
Date Sun, 05 Jan 2014 14:14:51 GMT

     [ https://issues.apache.org/jira/browse/HAMA-834?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Martin Illecker updated HAMA-834:
---------------------------------

    Attachment:     (was: HAMA-834.patch)

> Fix KMeans example
> ------------------
>
>                 Key: HAMA-834
>                 URL: https://issues.apache.org/jira/browse/HAMA-834
>             Project: Hama
>          Issue Type: Bug
>          Components: examples, machine learning
>    Affects Versions: 0.6.3
>            Reporter: Martin Illecker
>              Labels: example
>             Fix For: 0.7.0
>
>
> Fix problems in KMeans example and revise test case.
> 1) Typo \[1] and input path issue
> 2) Wrong *summationCount* in assignCentersInternal
> *summationCount* should also be incremented if \[2] 
> {code}
> if (clusterCenter == null) {
>   newCenterArray[lowestDistantCenter] = key;
> }
> {code}
> Otherwise *summationCount* may stay zero when only one value is assigned. Then this zero
will be propagated to *incrementSum* \[3] and might cause a divide by zero in \[4]. 
> By the way if we add three vectors and the *summationCount* would only be two, this will
lead to wrong results. Because later we are dividing the vector by the amount of increments.
> 3) Results depend on the amount *numBspTask*
> (results vary if *numBspTask* is changed)
> \[1]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/kmeans/KMeansBSP.java#L518-519
> \[2] https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/kmeans/KMeansBSP.java#L249
> \[3]
> https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/kmeans/KMeansBSP.java#L161
> \[4] https://github.com/apache/hama/blob/trunk/ml/src/main/java/org/apache/hama/ml/kmeans/KMeansBSP.java#L172



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