Merge pull request #453 from markhamstra/commutative

Change docs on 'reduce' since the merging of local reduces no longer pre...

core/src/main/scala/spark/RDD.scala

@@ -378,7 +378,7 @@ abstract class RDD[T: ClassManifest](
   }
 
   /**
-   * Reduces the elements of this RDD using the specified associative binary operator.
+   * Reduces the elements of this RDD using the specified commutative and associative binary operator.
    */
   def reduce(f: (T, T) => T): T = {
     val cleanF = sc.clean(f)

core/src/main/scala/spark/api/java/JavaRDDLike.scala

@@ -201,7 +201,7 @@ trait JavaRDDLike[T, This <: JavaRDDLike[T, This]] extends PairFlatMapWorkaround
   }
 
   /**
-   * Reduces the elements of this RDD using the specified associative binary operator.
+   * Reduces the elements of this RDD using the specified commutative and associative binary operator.
    */
   def reduce(f: JFunction2[T, T, T]): T = rdd.reduce(f)
 

docs/scala-programming-guide.md

@@ -203,7 +203,7 @@ A complete list of transformations is available in the [RDD API doc](api/core/in
 <tr><th>Action</th><th>Meaning</th></tr>
 <tr>
   <td> <b>reduce</b>(<i>func</i>) </td>
-  <td> Aggregate the elements of the dataset using a function <i>func</i> (which takes two arguments and returns one). The function should be associative so that it can be computed correctly in parallel. </td>
+  <td> Aggregate the elements of the dataset using a function <i>func</i> (which takes two arguments and returns one). The function should be commutative and associative so that it can be computed correctly in parallel. </td>
 </tr>
 <tr>
   <td> <b>collect</b>() </td>