org.apache.spark.util

Class AccumulatorV2<IN,OUT>

Object

org.apache.spark.util.AccumulatorV2<IN,OUT>

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

CollectionAccumulator, DoubleAccumulator, LongAccumulator, MapperRowCounter

public abstract class AccumulatorV2<IN,OUT>
extends Object
implements scala.Serializable

The base class for accumulators, that can accumulate inputs of type IN, and produce output of type OUT.

OUT should be a type that can be read atomically (e.g., Int, Long), or thread-safely (e.g., synchronized collections) because it will be read from other threads.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
AccumulatorV2()

Method Summary

Modifier and Type	Method and Description
abstract void	add(IN v) Takes the inputs and accumulates.
abstract AccumulatorV2<IN,OUT>	copy() Creates a new copy of this accumulator.
AccumulatorV2<IN,OUT>	copyAndReset() Creates a new copy of this accumulator, which is zero value.
long	id() Returns the id of this accumulator, can only be called after registration.
boolean	isRegistered() Returns true if this accumulator has been registered.
abstract boolean	isZero() Returns if this accumulator is zero value or not.
abstract void	merge(AccumulatorV2<IN,OUT> other) Merges another same-type accumulator into this one and update its state, i.e.
scala.Option<String>	name() Returns the name of this accumulator, can only be called after registration.
abstract void	reset() Resets this accumulator, which is zero value.
String	toString()
abstract OUT	value() Defines the current value of this accumulator

Methods inherited from class Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

AccumulatorV2

public AccumulatorV2()

Method Detail

add

public abstract void add(IN v)

Takes the inputs and accumulates.

Parameters:

v - (undocumented)

copy

public abstract AccumulatorV2<IN,OUT> copy()

Creates a new copy of this accumulator.

Returns:

(undocumented)

copyAndReset

public AccumulatorV2<IN,OUT> copyAndReset()

Creates a new copy of this accumulator, which is zero value. i.e. call isZero on the copy must return true.

Returns:

(undocumented)

id

public final long id()

Returns the id of this accumulator, can only be called after registration.

Returns:

(undocumented)

isRegistered

public final boolean isRegistered()

Returns true if this accumulator has been registered.

Returns:

(undocumented)

Note:

All accumulators must be registered before use, or it will throw exception.

isZero

public abstract boolean isZero()

Returns if this accumulator is zero value or not. e.g. for a counter accumulator, 0 is zero value; for a list accumulator, Nil is zero value.

Returns:

(undocumented)

merge

public abstract void merge(AccumulatorV2<IN,OUT> other)

Merges another same-type accumulator into this one and update its state, i.e. this should be merge-in-place.

Parameters:

other - (undocumented)

name

public final scala.Option<String> name()

Returns the name of this accumulator, can only be called after registration.

Returns:

(undocumented)

reset

public abstract void reset()

Resets this accumulator, which is zero value. i.e. call isZero must return true.

toString

public String toString()

Overrides:

toString in class Object

value

public abstract OUT value()

Defines the current value of this accumulator

Returns:

(undocumented)