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https://issues.apache.org/jira/browse/SPARK-1227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14204762#comment-14204762
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Sean Owen commented on SPARK-1227:
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OK you're interested in detecting overfitting, for one? You can't compare 
algorithms with a different objective function this way though, right? a 
different regularization param alone means a different objective. So I don't 
see it can be a general benchmark, and other classifier metrics are more 
appropriate. But yeah you could compare two runs that share the exact same 
objective, and that's a way of comparing training algorithms. 

Accuracy is in MulticlassMetrics which can be used with binary classification 
but it would be a nice to have for BinaryClassificationMetrics.

> Diagnostics for Classification&Regression
> -----------------------------------------
>
>                 Key: SPARK-1227
>                 URL: https://issues.apache.org/jira/browse/SPARK-1227
>             Project: Spark
>          Issue Type: Improvement
>          Components: MLlib
>            Reporter: Martin Jaggi
>            Assignee: Martin Jaggi
>
> Currently, the attained objective function is not computed (for efficiency 
> reasons, as one evaluation requires one full pass through the data).
> For diagnostics and comparing different algorithms, we should however provide 
> this as a separate function (one MR).
> Doing this requires the loss and regularizer functions themselves, not only 
> their gradients (which are currently in the Gradient class). How about adding 
> the new function directly on the corresponding models in classification/* and 
> regression/* ? Any thoughts?



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