[jira] [Commented] (HAMA-834) Fix KMeans example

["Edward J. Yoon (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HAMA-834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13862716#comment-13862716 ] 

Edward J. Yoon commented on HAMA-834:
-------------------------------------

Input generated incorrectly. There's a bug in generateInputText or prepareInputText methods. 

{code}
edward@edward-VirtualBox:~/workspace/hama-trunk$ ls -al /tmp/clustering/in/parts/
total 32
drwxr-xr-x 2 edward edward 4096 Jan  6 10:36 .
drwxr-xr-x 3 edward edward 4096 Jan  6 10:36 ..
-rwxrwxrwx 1 edward edward 1059 Jan  6 10:36 part0.seq
-rw-r--r-- 1 edward edward   20 Jan  6 10:36 .part0.seq.crc
-rwxrwxrwx 1 edward edward 1059 Jan  6 10:36 part1.seq
-rw-r--r-- 1 edward edward   20 Jan  6 10:36 .part1.seq.crc
-rwxrwxrwx 1 edward edward 2065 Jan  6 10:36 part2.seq
-rw-r--r-- 1 edward edward   28 Jan  6 10:36 .part2.seq.crc
{code}

> 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
>
>         Attachments: HAMA-834.patch
>
>
> 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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