[ 
https://issues.apache.org/jira/browse/SPARK-17134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15428848#comment-15428848
 ] 

DB Tsai commented on SPARK-17134:
---------------------------------

{code:borderStyle=solid}
val margins = Array.ofDim[Double](numClasses)
features.foreachActive { (index, value) =>
  if (featuresStd(index) != 0.0 && value != 0.0) {
    var i = 0
    val temp = value / featuresStd(index)
    while ( i < numClasses) {
      margins(i) += coefficients(i * numFeaturesPlusIntercept + index) * temp
      i += 1
   }
  }
}

if (fitIntercept) {
  var i = 0
  val length = features.size
  while ( i < numClasses) {
    margins(i) += coefficients(i * numFeaturesPlusIntercept + length)
    i += 1
  }
}

val maxMargin = margins.max
val marginOfLabel = margins(label.toInt)
{code}


> Use level 2 BLAS operations in LogisticAggregator
> -------------------------------------------------
>
>                 Key: SPARK-17134
>                 URL: https://issues.apache.org/jira/browse/SPARK-17134
>             Project: Spark
>          Issue Type: Sub-task
>          Components: ML
>            Reporter: Seth Hendrickson
>
> Multinomial logistic regression uses LogisticAggregator class for gradient 
> updates. We should look into refactoring MLOR to use level 2 BLAS operations 
> for the updates. Performance testing should be done to show improvements.



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