[jira] [Commented] (MAHOUT-1155) Make MatrixSlice a Vector and fix Centroid cloning

["Ted Dunning (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAHOUT-1155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13596800#comment-13596800 ] 

Ted Dunning commented on MAHOUT-1155:
-------------------------------------

In this patch fragment:

+  @Override
+  public Centroid clone() {
+    return new Centroid(super.clone());
+  }

Doesn't this double allocate?  The Centroid(Vector) constructor is patched thusly:

   public Centroid(WeightedVector original) {
-    super(original.getWeight(), original.getIndex());
-    delegate = original.getVector().like();
-    delegate.assign(original);
+    super(original.getVector().like().assign(original), original.getWeight(), original.getIndex());
   }

And this seems to allocate a new vector with the like().  That means that the argument here which was cloned is now liked.

This is different from the WeightedVector case because the DelegatingVector constructor only retains a reference rather than reallocate its argument.

Can the clone in Centroid just clone super and return it with a cast?

                
> Make MatrixSlice a Vector and fix Centroid cloning
> --------------------------------------------------
>
>                 Key: MAHOUT-1155
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-1155
>             Project: Mahout
>          Issue Type: Improvement
>          Components: Math
>    Affects Versions: 0.8
>            Reporter: Dan Filimon
>            Priority: Minor
>         Attachments: MAHOUT_1155.patch
>
>
> There are two changes in this issue:
> - making MatrixSlice a Vector by extending DelegatingVector;
> - making a few changes to the vector cloning code so that when cloning a Centroid, the result is also a Centroid.
> This is part of the changes in https://issues.apache.org/jira/browse/MAHOUT-1154

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