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https://issues.apache.org/jira/browse/MAHOUT-300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12836169#action_12836169
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Robin Anil commented on MAHOUT-300:
-----------------------------------

An issue i found here was for empty dense vectors

IterateNonZero() optimises for iterating over non zero elements hence result is 
still -INF
getNumNonDefaultElements() == size hence it returns -INF instead of zero. 

I guess i will have to go with a bool hasNoElements/checkedNoElements based 
solution

> Solve performance issues with Vector Implementations
> ----------------------------------------------------
>
>                 Key: MAHOUT-300
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-300
>             Project: Mahout
>          Issue Type: Improvement
>    Affects Versions: 0.3
>            Reporter: Robin Anil
>             Fix For: 0.3
>
>         Attachments: MAHOUT-300.patch
>
>
> AbstractVector operations like times
>   public Vector times(double x) {
>     Vector result = clone();
>     Iterator<Element> iter = iterateNonZero();
>     while (iter.hasNext()) {
>       Element element = iter.next();
>       int index = element.index();
>       result.setQuick(index, element.get() * x);
>     }
>     return result;
>   }
> should be implemented as follows
>  public Vector times(double x) {
>     Vector result = clone();
>     Iterator<Element> iter = result.iterateNonZero();
>     while (iter.hasNext()) {
>       Element element = iter.next();
>       element.set(element.get() * x);
>     }
>     return result;
>   }

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