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https://issues.apache.org/jira/browse/MAHOUT-2019?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16257423#comment-16257423
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ASF GitHub Bot commented on MAHOUT-2019:
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Github user pferrel commented on the issue:
https://github.com/apache/mahout/pull/342
Yes, will merge today
> 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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