[jira] [Assigned] (MAHOUT-1959) BallKMeans.iterativeAssignment can set wrong weights.

["Andrew Musselman (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAHOUT-1959?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Musselman reassigned MAHOUT-1959:
----------------------------------------

    Assignee: Shashanka Balakuntala Srinivasa

> BallKMeans.iterativeAssignment can set wrong weights.
> -----------------------------------------------------
>
>                 Key: MAHOUT-1959
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-1959
>             Project: Mahout
>          Issue Type: Bug
>            Reporter: Hao Zhong
>            Assignee: Shashanka Balakuntala Srinivasa
>            Priority: Major
>
> I notice that the BallKMeans.iterativeAssignment method uses the following code to calculate weights:
> {code:title=BallKMeans.java|borderStyle=solid}
> for (WeightedVector datapoint : datapoints) {
>         Centroid closestCentroid = (Centroid) centroids.searchFirst(datapoint, false).getValue();
>         closestCentroid.setWeight(closestCentroid.getWeight() + datapoint.getWeight());
>       }
> {code}
> In MAHOUT-1237, the buggy code is the same way to calculate the weight:
> {code:title=ClusteringUtils.java|borderStyle=solid}
> for (Vector vector : datapoints) {
>       Centroid closest = (Centroid) centroids.searchFirst(vector, false).getValue();
>       totalCost += closest.getWeight();
>     }
> {code}
> The fixed code is as follow:
> {code:title=ClusteringUtils.java|borderStyle=solid}
> for (Vector vector : datapoints) {
>       totalCost += centroids.searchFirst(vector, false).getWeight();
>     }
> {code}
> I am not quite sure whether BallKMeans.iterativeAssignment sets the right weights. Please check it.



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