org.apache.spark

Interface AccumulableParam<R,T>

All Superinterfaces:

java.io.Serializable

All Known Subinterfaces:

AccumulatorParam<T>

All Known Implementing Classes:

GrowableAccumulableParam, SparkContext.DoubleAccumulatorParam$, SparkContext.FloatAccumulatorParam$, SparkContext.IntAccumulatorParam$, SparkContext.LongAccumulatorParam$, Vector.VectorAccumParam$

public interface AccumulableParam<R,T>
extends java.io.Serializable

Helper object defining how to accumulate values of a particular type. An implicit AccumulableParam needs to be available when you create Accumulables of a specific type.

Method Summary

Methods

Modifier and Type	Method and Description
R	addAccumulator(R r, T t) Add additional data to the accumulator value.
R	addInPlace(R r1, R r2) Merge two accumulated values together.
R	zero(R initialValue) Return the "zero" (identity) value for an accumulator type, given its initial value.

Method Detail

addAccumulator

R addAccumulator(R r,
               T t)

Add additional data to the accumulator value. Is allowed to modify and return r for efficiency (to avoid allocating objects).

Parameters:

r - the current value of the accumulator

t - the data to be added to the accumulator

Returns:

the new value of the accumulator

addInPlace

R addInPlace(R r1,
           R r2)

Merge two accumulated values together. Is allowed to modify and return the first value for efficiency (to avoid allocating objects).

Parameters:

r1 - one set of accumulated data

r2 - another set of accumulated data

Returns:

both data sets merged together

zero

R zero(R initialValue)

Return the "zero" (identity) value for an accumulator type, given its initial value. For example, if R was a vector of N dimensions, this would return a vector of N zeroes.