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https://issues.apache.org/jira/browse/MAHOUT-2019?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Musselman updated MAHOUT-2019:
-------------------------------------
    Fix Version/s:     (was: 0.14.1)
                   14.2

> 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
>            Priority: Major
>             Fix For: 14.2
>
>
> 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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