diff options
| -rw-r--r-- | core/src/main/scala/org/apache/spark/rdd/RDD.scala | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/core/src/main/scala/org/apache/spark/rdd/RDD.scala b/core/src/main/scala/org/apache/spark/rdd/RDD.scala index de7102f5b6..53e01a0dbf 100644 --- a/core/src/main/scala/org/apache/spark/rdd/RDD.scala +++ b/core/src/main/scala/org/apache/spark/rdd/RDD.scala @@ -970,6 +970,13 @@ abstract class RDD[T: ClassTag]( * apply the fold to each element sequentially in some defined ordering. For functions * that are not commutative, the result may differ from that of a fold applied to a * non-distributed collection. + * + * @param zeroValue the initial value for the accumulated result of each partition for the `op` + * operator, and also the initial value for the combine results from different + * partitions for the `op` operator - this will typically be the neutral + * element (e.g. `Nil` for list concatenation or `0` for summation) + * @param op an operator used to both accumulate results within a partition and combine results + * from different partitions */ def fold(zeroValue: T)(op: (T, T) => T): T = withScope { // Clone the zero value since we will also be serializing it as part of tasks @@ -988,6 +995,13 @@ abstract class RDD[T: ClassTag]( * and one operation for merging two U's, as in scala.TraversableOnce. Both of these functions are * allowed to modify and return their first argument instead of creating a new U to avoid memory * allocation. + * + * @param zeroValue the initial value for the accumulated result of each partition for the + * `seqOp` operator, and also the initial value for the combine results from + * different partitions for the `combOp` operator - this will typically be the + * neutral element (e.g. `Nil` for list concatenation or `0` for summation) + * @param seqOp an operator used to accumulate results within a partition + * @param combOp an associative operator used to combine results from different partitions */ def aggregate[U: ClassTag](zeroValue: U)(seqOp: (U, T) => U, combOp: (U, U) => U): U = withScope { // Clone the zero value since we will also be serializing it as part of tasks |