org.apache.giraph.reducers

Class Reducer<S,R extends org.apache.hadoop.io.Writable>

java.lang.Object

org.apache.giraph.reducers.Reducer<S,R>

Type Parameters:

S - Single value type, objects passed on workers

R - Reduced value type

public class Reducer<S,R extends org.apache.hadoop.io.Writable>
extends Object

Object responsible for performing reducing operation. Simple wrapper of ReduceOperation object and current value holding partially reduced result.

Constructor Summary

Constructors

Constructor and Description
Reducer() Constructor
Reducer(ReduceOperation<S,R> reduceOp) Constructor
Reducer(ReduceOperation<S,R> reduceOp, R currentValue) Constructor

Method Summary

Modifier and Type	Method and Description
R	createInitialValue() Return new initial reduced value.
R	getCurrentValue()
ReduceOperation<S,R>	getReduceOp()
void	readFields(DataInput in, ImmutableClassesGiraphConfiguration conf) Deserialize the fields of this object from in.
void	reduce(S valueToReduce) Reduce given value into current reduced value.
void	reduceMerge(R valueToReduce) Reduce given partially reduced value into current reduced value.
void	setCurrentValue(R currentValue)
void	write(DataOutput out) Serialize the fields of this object to out.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Reducer

public Reducer()

Constructor

Reducer

public Reducer(ReduceOperation<S,R> reduceOp)

Constructor

Parameters:

reduceOp - Reduce operations

Reducer

public Reducer(ReduceOperation<S,R> reduceOp,
               R currentValue)

Constructor

Parameters:

reduceOp - Reduce operations

currentValue - current reduced value

Method Detail

reduce

public void reduce(S valueToReduce)

Reduce given value into current reduced value.

Parameters:

valueToReduce - Single value to reduce

reduceMerge

public void reduceMerge(R valueToReduce)

Reduce given partially reduced value into current reduced value.

Parameters:

valueToReduce - Partial value to reduce

createInitialValue

public R createInitialValue()

Return new initial reduced value.

Returns:

New initial reduced value

getReduceOp

public ReduceOperation<S,R> getReduceOp()

getCurrentValue

public R getCurrentValue()

setCurrentValue

public void setCurrentValue(R currentValue)

write

public void write(DataOutput out)
           throws IOException

Serialize the fields of this object to out.

Parameters:

out - DataOuput to serialize this object into.

Throws:

IOException

readFields

public void readFields(DataInput in,
                       ImmutableClassesGiraphConfiguration conf)
                throws IOException

Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Parameters:

in - DataInput to deseriablize this object from.

conf - Configuration

Throws:

IOException