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https://issues.apache.org/jira/browse/SPARK-16470?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Weichen Xu updated SPARK-16470:
-------------------------------
    Description: 
In `ml.regression.LinearRegression`, it use breeze `LBFGS` and `OWLQN` 
optimizer to do data training,  but do not check whether breeze's optimizer 
returned result  actually reached convergence.

In fact, the  `LBFGS` and `OWLQN`  optimizer in breeze finish iteration may 
result in the following situations:

1) reach max iteration number
2) function reach value convergence
3) objective function stop improving
4) gradient reach convergence
5) search failed(due to some internal numerical error)

only (2) & (4) situations above can be regarded as convergence result.
in other situation, we should at least print some warning to remind spark user.



  was:
In `ml.regression.LinearRegression`, it use breeze `LBFGS` and `OWLQN` 
optimizer to do data training,  but do not check whether breeze's optimizer 
returned result  actually reached convergence.

In fact, the  `LBFGS` and `OWLQN`  optimizer in breeze finish iteration may 
result the following situations:

1) reach max iteration number
2) function reach value convergence
3) objective function stop improving
4) gradient reach convergence
5) search failed(due to some internal numerical error)

only (2) & (4) situations above can be regarded as convergence result.
in other situation, we should at least print some warning to remind spark user.




> ml.regression.LinearRegression training data do not check whether the result 
> actually reach convergence
> -------------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-16470
>                 URL: https://issues.apache.org/jira/browse/SPARK-16470
>             Project: Spark
>          Issue Type: Improvement
>          Components: ML, Optimizer
>    Affects Versions: 2.0.1, 2.1.0
>            Reporter: Weichen Xu
>   Original Estimate: 24h
>  Remaining Estimate: 24h
>
> In `ml.regression.LinearRegression`, it use breeze `LBFGS` and `OWLQN` 
> optimizer to do data training,  but do not check whether breeze's optimizer 
> returned result  actually reached convergence.
> In fact, the  `LBFGS` and `OWLQN`  optimizer in breeze finish iteration may 
> result in the following situations:
> 1) reach max iteration number
> 2) function reach value convergence
> 3) objective function stop improving
> 4) gradient reach convergence
> 5) search failed(due to some internal numerical error)
> only (2) & (4) situations above can be regarded as convergence result.
> in other situation, we should at least print some warning to remind spark 
> user.



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