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https://issues.apache.org/jira/browse/SPARK-17824?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yanbo Liang updated SPARK-17824:
--------------------------------
    Description: 
Cholesky decomposition is unstable (for near-singular and rank deficient 
matrices), it was often used when matrix A is very large and sparse due to 
faster calculation. QR decomposition has better numerical properties than 
Cholesky. Spark MLlib {{WeightedLeastSquares}} use Cholesky decomposition to 
solve normal equation currently, we should also support or move to QR solver 
for better stability.

cc [~dbtsai] [~sethah]

  was:Cholesky decomposition is unstable (for near-singular and rank deficient 
matrices), it was often used when matrix A is very large and sparse due to 
faster calculation. QR decomposition has better numerical properties than 
Cholesky. Spark MLlib {{WeightedLeastSquares}} use Cholesky decomposition to 
solve normal equation currently, we should also support or move to QR solver 
for better stability.


> QR solver for WeightedLeastSquares
> ----------------------------------
>
>                 Key: SPARK-17824
>                 URL: https://issues.apache.org/jira/browse/SPARK-17824
>             Project: Spark
>          Issue Type: New Feature
>          Components: ML
>            Reporter: Yanbo Liang
>            Assignee: Yanbo Liang
>
> Cholesky decomposition is unstable (for near-singular and rank deficient 
> matrices), it was often used when matrix A is very large and sparse due to 
> faster calculation. QR decomposition has better numerical properties than 
> Cholesky. Spark MLlib {{WeightedLeastSquares}} use Cholesky decomposition to 
> solve normal equation currently, we should also support or move to QR solver 
> for better stability.
> cc [~dbtsai] [~sethah]



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