Rectify gereneric parameter names between SparkContext and AccumulablePa...

AccumulableParam gave its generic parameters as 'R, T', whereas SparkContext labeled them 'T, R'.

Trivial, but really confusing.

I resolved this in favor of AccumulableParam, because it seemed to have some logic for its names.  I also extended this minimal, but at least present, justification into the SparkContext comments.

Author: Nathan Kronenfeld <nkronenfeld@oculusinfo.com>

Closes #2637 from nkronenfeld/accumulators and squashes the following commits:

98d6b74 [Nathan Kronenfeld] Rectify gereneric parameter names between SparkContext and AccumulableParam

1 files changed, 6 insertions, 6 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index 97109b9f41..396cdd1247 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -779,20 +779,20 @@ class SparkContext(config: SparkConf) extends Logging {
   /**
    * Create an [[org.apache.spark.Accumulable]] shared variable, to which tasks can add values
    * with `+=`. Only the driver can access the accumuable's `value`.
-   * @tparam T accumulator type
-   * @tparam R type that can be added to the accumulator
+   * @tparam R accumulator result type
+   * @tparam T type that can be added to the accumulator
    */
-  def accumulable[T, R](initialValue: T)(implicit param: AccumulableParam[T, R]) =
+  def accumulable[R, T](initialValue: R)(implicit param: AccumulableParam[R, T]) =
     new Accumulable(initialValue, param)
 
   /**
    * Create an [[org.apache.spark.Accumulable]] shared variable, with a name for display in the
    * Spark UI. Tasks can add values to the accumuable using the `+=` operator. Only the driver can
    * access the accumuable's `value`.
-   * @tparam T accumulator type
-   * @tparam R type that can be added to the accumulator
+   * @tparam R accumulator result type
+   * @tparam T type that can be added to the accumulator
    */
-  def accumulable[T, R](initialValue: T, name: String)(implicit param: AccumulableParam[T, R]) =
+  def accumulable[R, T](initialValue: R, name: String)(implicit param: AccumulableParam[R, T]) =
     new Accumulable(initialValue, param, Some(name))
 
   /**