[jira] [Created] (MAHOUT-2019) SparseRowMatrix assign ops user for loops instead of iterateNonZero and so can be optimized

["Pat Ferrel (JIRA)" <ji...@apache.org>]

Pat Ferrel created MAHOUT-2019:
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             Summary: 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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