Antoine Galataud created SPARK-24875:
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Summary: MulticlassMetrics should offer a more efficient way to
compute count by label
Key: SPARK-24875
URL: https://issues.apache.org/jira/browse/SPARK-24875
Project: Spark
Issue Type: Improvement
Components: MLlib
Affects Versions: 2.3.1
Reporter: Antoine Galataud
Currently _MulticlassMetrics_ calls _countByValue_() to get count by class/label
{code:java}
private lazy val labelCountByClass: Map[Double, Long] =
predictionAndLabels.values.countByValue()
{code}
If input _RDD[(Double, Double)]_ is huge (which can be the case with a large
test dataset), it will lead to poor execution performance.
One option could be to allow using _countByValueApprox_ (could require adding
an extra configuration param for MulticlassMetrics).
Note: since there is no equivalent of _MulticlassMetrics_ in new ML library, I
don't know how this could be ported there.
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