Dmitriy Lyubimov created MAHOUT-1298:
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Summary: SparseRowMatrix,SparseColMatrix: optimize transpose()
Key: MAHOUT-1298
URL: https://issues.apache.org/jira/browse/MAHOUT-1298
Project: Mahout
Issue Type: New Feature
Components: Math
Affects Versions: 0.8
Reporter: Dmitriy Lyubimov
Assignee: Dmitriy Lyubimov
Fix For: 0.9
these matrices lack optimized transpose and rely onto AbstractMatrix's O(mn)
implementation which is not cool for very sparse subblocks.
proposal is to implement a custom transpose with two things in mind:
1) transpose result to row sparse matrix should be col sparse matrix, and vice
versa (and not from default like() as default implementation would take);
2) obviously, iterate only thru non-zero elements only of all rows(columns).
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