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From dbtsai <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-4431][MLlib] Implement efficient active...
Date Thu, 20 Nov 2014 23:48:11 GMT
Github user dbtsai commented on a diff in the pull request:

    https://github.com/apache/spark/pull/3288#discussion_r20687461
  
    --- Diff: mllib/src/main/scala/org/apache/spark/mllib/stat/MultivariateOnlineSummarizer.scala
---
    @@ -95,22 +93,7 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary
with S
         require(n == sample.size, s"Dimensions mismatch when adding new sample." +
           s" Expecting $n but got ${sample.size}.")
     
    -    sample match {
    -      case dv: DenseVector => {
    -        var j = 0
    -        while (j < dv.size) {
    -          add(j, dv.values(j))
    -          j += 1
    -        }
    -      }
    -      case sv: SparseVector =>
    -        var j = 0
    -        while (j < sv.indices.size) {
    -          add(sv.indices(j), sv.values(j))
    -          j += 1
    -        }
    -      case v => throw new IllegalArgumentException("Do not support vector type " +
v.getClass)
    -    }
    +    sample.foreach(true)(x => add(x._1, x._2))
    --- End diff --
    
    This will be faster than 
    ```scala
    sample.foreach(true){
      case (index, value) => add(index, value) 
    }
    ```
    for 5%. 
    
    See the generated bytecode.
    
    With pattern matching.
    ```
       L20
        LINENUMBER 103 L20
        ALOAD 4
        INVOKEVIRTUAL scala/Tuple2._1$mcI$sp ()I
        ISTORE 5
       L21
        ALOAD 4
        INVOKEVIRTUAL scala/Tuple2._2$mcD$sp ()D
        DSTORE 6
       L22
        ALOAD 0
        ILOAD 5
        DLOAD 6
        INVOKEVIRTUAL org/apache/spark/mllib/stat/MultivariateOnlineSummarizer.org$apache$spark$mllib$stat$MultivariateOnlineSummarizer$$add
(ID)V
        GETSTATIC scala/runtime/BoxedUnit.UNIT : Lscala/runtime/BoxedUnit;
        ASTORE 8
    ```
    Without pattern matching.
    ```
       L17
        LINENUMBER 100 L17
        ALOAD 0
        ALOAD 3
        INVOKEVIRTUAL scala/Tuple2._1$mcI$sp ()I
        ALOAD 3
        INVOKEVIRTUAL scala/Tuple2._2$mcD$sp ()D
        INVOKEVIRTUAL org/apache/spark/mllib/stat/MultivariateOnlineSummarizer.org$apache$spark$mllib$stat$MultivariateOnlineSummarizer$$add
(ID)V
    ```


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