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https://issues.apache.org/jira/browse/SPARK-19746?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-19746:
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Assignee: Apache Spark
> LogisticAggregator is inefficient in indexing
> ---------------------------------------------
>
> Key: SPARK-19746
> URL: https://issues.apache.org/jira/browse/SPARK-19746
> Project: Spark
> Issue Type: Improvement
> Components: ML
> Affects Versions: 2.1.0
> Reporter: Seth Hendrickson
> Assignee: Apache Spark
>
> The following code occurs in the `LogisticAggregator.add` method, which is a
> performance critical path.
> {code}
> val localCoefficients = bcCoefficients.value
> features.foreachActive { (index, value) =>
> val stdValue = value / localFeaturesStd(index)
> var j = 0
> while (j < numClasses) {
> margins(j) += localCoefficients(index * numClasses + j) * stdValue
> j += 1
> }
> }
> {code}
> `llocalCoefficients(index * numClasses + j)` calls the `apply` method on
> `Vector`, which dispatches to `asBreeze(index * numClasses + j)` which
> creates a new Breeze vector, and then indexes it. This is very inefficient,
> creates a lot of unnecessary garbage, and we can avoid it by indexing the
> underlying array.
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