changes to accumulator to add objects in-place.

src/examples/Vector.scala

@@ -57,7 +57,7 @@ object Vector {
   implicit def doubleToMultiplier(num: Double) = new Multiplier(num)
 
   implicit object VectorAccumParam extends spark.AccumulatorParam[Vector] {
-    def add(t1: Vector, t2: Vector) = t1 + t2
+    def addInPlace(t1: Vector, t2: Vector) = t1 + t2
     def zero(initialValue: Vector) = Vector.zeros(initialValue.length)
   }
 }

src/scala/spark/Accumulators.scala

@@ -4,15 +4,17 @@ import java.io._
 
 import scala.collection.mutable.Map
 
-@serializable class Accumulator[T](initialValue: T, param: AccumulatorParam[T])
+@serializable class Accumulator[T](
+  @transient initialValue: T, param: AccumulatorParam[T])
 {
   val id = Accumulators.newId
-  @transient var value_ = initialValue
+  @transient var value_ = initialValue // Current value on master
+  val zero = param.zero(initialValue)  // Zero value to be passed to workers
   var deserialized = false
 
   Accumulators.register(this)
 
-  def += (term: T) { value_ = param.add(value_, term) }
+  def += (term: T) { value_ = param.addInPlace(value_, term) }
   def value = this.value_
   def value_= (t: T) {
     if (!deserialized) value_ = t
@@ -22,7 +24,7 @@ import scala.collection.mutable.Map
   // Called by Java when deserializing an object
   private def readObject(in: ObjectInputStream) {
     in.defaultReadObject
-    value_ = param.zero(initialValue)
+    value_ = zero
     deserialized = true
     Accumulators.register(this)
   }
@@ -31,7 +33,7 @@ import scala.collection.mutable.Map
 }
 
 @serializable trait AccumulatorParam[T] {
-  def add(t1: T, t2: T): T
+  def addInPlace(t1: T, t2: T): T
   def zero(initialValue: T): T
 }
 

src/scala/spark/MesosScheduler.scala

@@ -304,6 +304,7 @@ extends ParallelOperation
       val result = Utils.deserialize[TaskResult[T]](status.getData)
       results(tidToIndex(tid)) = result.value
       // Update accumulators
+      print(" with " + result.accumUpdates.size + " accumulatedUpdates")
       Accumulators.add(callingThread, result.accumUpdates)
       // Mark finished and stop if we've finished all the tasks
       finished(tidToIndex(tid)) = true

src/scala/spark/SparkContext.scala

@@ -82,11 +82,11 @@ class SparkContext(master: String, frameworkName: String) {
 
 object SparkContext {
   implicit object DoubleAccumulatorParam extends AccumulatorParam[Double] {
-    def add(t1: Double, t2: Double): Double = t1 + t2
+    def addInPlace(t1: Double, t2: Double): Double = t1 + t2
     def zero(initialValue: Double) = 0.0
   }
   implicit object IntAccumulatorParam extends AccumulatorParam[Int] {
-    def add(t1: Int, t2: Int): Int = t1 + t2
+    def addInPlace(t1: Int, t2: Int): Int = t1 + t2
     def zero(initialValue: Int) = 0
   }
   // TODO: Add AccumulatorParams for other types, e.g. lists and strings