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https://issues.apache.org/jira/browse/MAHOUT-2019?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16258207#comment-16258207
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Hudson commented on MAHOUT-2019:
--------------------------------

FAILURE: Integrated in Jenkins build Mahout-Quality #3511 (See 
[https://builds.apache.org/job/Mahout-Quality/3511/])
MAHOUT-2019 SparkRow Matrix Speedup and fixing change to scala 2.11 made (pat: 
rev 800a9ed6d7e015aa82b9eb7624bb441b71a8f397)
* (edit) math/src/main/java/org/apache/mahout/math/SparseRowMatrix.java


> SparseRowMatrix assign ops user for loops instead of iterateNonZero and so 
> can be optimized
> -------------------------------------------------------------------------------------------
>
>                 Key: MAHOUT-2019
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-2019
>             Project: Mahout
>          Issue Type: Bug
>          Components: Math
>    Affects Versions: 0.13.0
>            Reporter: Pat Ferrel
>            Assignee: Pat Ferrel
>             Fix For: 0.13.1
>
>
> DRMs get blockified into SparseRowMatrix instances if the density is low. But 
> SRM inherits the implementation of method like "assign" from AbstractMatrix, 
> which uses nest for loops to traverse rows. For multiplying 2 matrices that 
> are extremely sparse, the kind if data you see in collaborative filtering, 
> this is extremely wasteful of execution time. Better to use a sparse vector's 
> iterateNonZero Iterator for some function types.



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