GitHub user hhbyyh opened a pull request:

    https://github.com/apache/spark/pull/5909

    [SPARK-7368][MLlib] Add QR decomposition for RowMatrix

    jira: https://issues.apache.org/jira/browse/SPARK-7368 
    Add QR decomposition for RowMatrix. 
    
    I'm not sure what's the blueprint about the distributed Matrix from 
community and whether this will be a desirable feature , so I sent a prototype 
for discussion. I'll go on polish the code and provide ut and performance 
statistics if it's acceptable.
    
    The implementation refers to the [paper: 
https://www.cs.purdue.edu/homes/dgleich/publications/Constantine%202011%20-%20TSQR.pdf]
    Austin R. Benson, David F. Gleich, James Demmel. "Direct QR factorizations 
for tall-and-skinny matrices in MapReduce architectures", 2013 IEEE 
International Conference on Big Data,
    
    which is a stable algorithm with good scalability.
    
    Currently I tried it on a 400000 * 500 rowMatrix and it can bring down the 
computation time from 8.8 mins (using breeze.linalg.qr.reduced)  to 2.6 mins on 
a 4 worker cluster. I think there will still be some root for performance 
improvement.
    
    Any trial and suggestion is welcome.


You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/hhbyyh/spark qrDecomposition

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/spark/pull/5909.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #5909
    
----
commit 39b0b227d3bedfc789743972f5a0ded8583e8e7b
Author: Yuhao Yang <[email protected]>
Date:   2015-05-05T11:51:51Z

    initial draft for discussion

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