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https://issues.apache.org/jira/browse/SPARK-5766?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14317961#comment-14317961
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Sean Owen commented on SPARK-5766:
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Given that RowMatrix is a row-by-row representation, it would have to be
vector-matrix multiplication I think. In principle I think you can leverage
native code here; the only question is whether it overcomes the overhead of the
call for typical inputs, but it's possible.
> Slow RowMatrix multiplication
> -----------------------------
>
> Key: SPARK-5766
> URL: https://issues.apache.org/jira/browse/SPARK-5766
> Project: Spark
> Issue Type: Improvement
> Components: MLlib
> Reporter: Amaru Cuba Gyllensten
> Priority: Minor
> Labels: matrix
>
> Looking at the source code for RowMatrix multiplication by a local matrix, it
> seems like it is going through all columnvectors of the matrix, doing
> pairwise dot product on each column.
> It seems like this could be sped up by using gemm, performing full
> matrix-matrix multiplication on the local data, (or gemv, for vector-matrix
> multiplication), as is done in BlockMatrix or Matrix.
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