Github user jkbradley commented on a diff in the pull request:

    https://github.com/apache/spark/pull/3636#discussion_r21724910
  
    --- Diff: 
mllib/src/main/scala/org/apache/spark/mllib/optimization/GradientDescent.scala 
---
    @@ -182,34 +203,46 @@ object GradientDescent extends Logging {
         var regVal = updater.compute(
           weights, Vectors.dense(new Array[Double](weights.size)), 0, 1, 
regParam)._2
     
    -    for (i <- 1 to numIterations) {
    -      val bcWeights = data.context.broadcast(weights)
    -      // Sample a subset (fraction miniBatchFraction) of the total data
    -      // compute and sum up the subgradients on this subset (this is one 
map-reduce)
    -      val (gradientSum, lossSum, miniBatchSize) = data.sample(false, 
miniBatchFraction, 42 + i)
    -        .treeAggregate((BDV.zeros[Double](n), 0.0, 0L))(
    -          seqOp = (c, v) => {
    -            // c: (grad, loss, count), v: (label, features)
    -            val l = gradient.compute(v._2, v._1, bcWeights.value, 
Vectors.fromBreeze(c._1))
    -            (c._1, c._2 + l, c._3 + 1)
    -          },
    -          combOp = (c1, c2) => {
    -            // c: (grad, loss, count)
    -            (c1._1 += c2._1, c1._2 + c2._2, c1._3 + c2._3)
    -          })
    -
    -      if (miniBatchSize > 0) {
    -        /**
    -         * NOTE(Xinghao): lossSum is computed using the weights from the 
previous iteration
    -         * and regVal is the regularization value computed in the previous 
iteration as well.
    -         */
    -        stochasticLossHistory.append(lossSum / miniBatchSize + regVal)
    -        val update = updater.compute(
    -          weights, Vectors.fromBreeze(gradientSum / 
miniBatchSize.toDouble), stepSize, i, regParam)
    -        weights = update._1
    -        regVal = update._2
    -      } else {
    -        logWarning(s"Iteration ($i/$numIterations). The size of sampled 
batch is zero")
    +    val b = new Breaks
    +    b.breakable {
    +      for (i <- 1 to numIterations) {
    +        val bcWeights = data.context.broadcast(weights)
    +        // Sample a subset (fraction miniBatchFraction) of the total data
    +        // compute and sum up the subgradients on this subset (this is one 
map-reduce)
    +        val (gradientSum, lossSum, miniBatchSize) = data.sample(false, 
miniBatchFraction, 42 + i)
    +          .treeAggregate((BDV.zeros[Double](n), 0.0, 0L))(
    +            seqOp = (c, v) => {
    +              // c: (grad, loss, count), v: (label, features)
    +              val l = gradient.compute(v._2, v._1, bcWeights.value, 
Vectors.fromBreeze(c._1))
    +              (c._1, c._2 + l, c._3 + 1)
    +            },
    +            combOp = (c1, c2) => {
    +              // c: (grad, loss, count)
    +              (c1._1 += c2._1, c1._2 + c2._2, c1._3 + c2._3)
    +            })
    +
    +        if (miniBatchSize > 0) {
    +          /**
    +           * NOTE(Xinghao): lossSum is computed using the weights from the 
previous iteration
    +           * and regVal is the regularization value computed in the 
previous iteration as well.
    +           */
    +          stochasticLossHistory.append(lossSum / miniBatchSize + regVal)
    +          val update = updater.compute(
    --- End diff --
    
    No need to split arguments across multiple lines; I would leave this as it 
was. It's OK to have a line wrap in the middle of the argument list, if needed 
to make each line < 100 chars.


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