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From "liutengfei (JIRA)" <j...@apache.org>
Subject [jira] [Closed] (ABDERA-303) CIReducer in kmeans doesn't work well
Date Thu, 27 Sep 2012 01:13:07 GMT

     [ https://issues.apache.org/jira/browse/ABDERA-303?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

liutengfei closed ABDERA-303.
-----------------------------

    
> CIReducer in kmeans doesn't work well
> -------------------------------------
>
>                 Key: ABDERA-303
>                 URL: https://issues.apache.org/jira/browse/ABDERA-303
>             Project: Abdera
>          Issue Type: Bug
>         Environment: hadoop:
>    hadoop-2.0.0-alpha: pseudo cluster and single node cluster
>    hadoop-1.0.3: pseudo cluster
>    hadoop-0.20.2:pseudo cluster
> mahout:
>    mahout-0.7
> os:
>    ubuntu 11.04
> jdk:
>    jdk1.6.0_27
>            Reporter: liutengfei
>
> the function reduce in mahout-0.7-kmeans-CIReducer.java doesn't work well as it looks
like.
>   protected void reduce(IntWritable key, Iterable<ClusterWritable> values, Context
context) throws IOException,
>       InterruptedException {
>     Iterator<ClusterWritable> iter = values.iterator();
>     ClusterWritable first = null;
>     while (iter.hasNext()) {
>       ClusterWritable cw = iter.next();
>       if (first == null) {
>         first = cw;
>       } else {
>         first.getValue().observe(cw.getValue());
>       }
>     }
>     List<Cluster> models = new ArrayList<Cluster>();
>     models.add(first.getValue());
>     classifier = new ClusterClassifier(models, policy);
>     classifier.close();
>     context.write(key, first);
>   }
> Apparently´╝î the variable "first" will collect all output data of maps. Actually but,
the value of "first" will change after the code "ClusterWritable cw = iter.next();", same
with this new variable "cw"! I don't why but running result shows that the code runs looks
like this:"ClusterWritable cw  = first = iter.next();".
> "cw" is a reference a to "iter"?
> is "iter.next" just change the value of "iter" itself to the next?

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