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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