org.apache.giraph.reducers.impl

Class PairReduce<S1,R1 extends org.apache.hadoop.io.Writable,S2,R2 extends org.apache.hadoop.io.Writable>

java.lang.Object

org.apache.giraph.reducers.impl.PairReduce<S1,R1,S2,R2>

Type Parameters:

S1 - First single value type

R1 - First reduced value type

S2 - Second single value type

R2 - Second reduced value type

All Implemented Interfaces:

ReduceOperation<org.apache.commons.lang3.tuple.Pair<S1,S2>,PairWritable<R1,R2>>, org.apache.hadoop.io.Writable

public class PairReduce<S1,R1 extends org.apache.hadoop.io.Writable,S2,R2 extends org.apache.hadoop.io.Writable>
extends Object
implements ReduceOperation<org.apache.commons.lang3.tuple.Pair<S1,S2>,PairWritable<R1,R2>>

Combines two individual reducers, to create a single reducer of pairs that reduces each of them individually.

Constructor Summary

Constructors

Constructor and Description
PairReduce() Constructor
PairReduce(ReduceOperation<S1,R1> reduce1, ReduceOperation<S2,R2> reduce2) Constructor

Method Summary

Modifier and Type	Method and Description
PairWritable<R1,R2>	createInitialValue() Return new reduced value which is neutral to reduce operation.
void	readFields(DataInput in)
PairWritable<R1,R2>	reduce(PairWritable<R1,R2> curValue, org.apache.commons.lang3.tuple.Pair<S1,S2> valueToReduce) Add a new value.
PairWritable<R1,R2>	reduceMerge(PairWritable<R1,R2> curValue, PairWritable<R1,R2> valueToReduce) Add partially reduced value to current partially reduced value.
void	write(DataOutput out)

Methods inherited from class java.lang.Object

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

Constructor Detail

PairReduce

public PairReduce()

Constructor

PairReduce

public PairReduce(ReduceOperation<S1,R1> reduce1,
                  ReduceOperation<S2,R2> reduce2)

Constructor

Parameters:

reduce1 - First reduceOp

reduce2 - Second reduceOp

Method Detail

createInitialValue

public PairWritable<R1,R2> createInitialValue()

Description copied from interface: ReduceOperation

Return new reduced value which is neutral to reduce operation.

Specified by:

createInitialValue in interface ReduceOperation<org.apache.commons.lang3.tuple.Pair<S1,S2>,PairWritable<R1 extends org.apache.hadoop.io.Writable,R2 extends org.apache.hadoop.io.Writable>>

Returns:

Neutral value

reduce

public PairWritable<R1,R2> reduce(PairWritable<R1,R2> curValue,
                                  org.apache.commons.lang3.tuple.Pair<S1,S2> valueToReduce)

Description copied from interface: ReduceOperation

Add a new value. Needs to be commutative and associative Commonly, returned value should be same as curValue argument.

Specified by:

reduce in interface ReduceOperation<org.apache.commons.lang3.tuple.Pair<S1,S2>,PairWritable<R1 extends org.apache.hadoop.io.Writable,R2 extends org.apache.hadoop.io.Writable>>

Parameters:

curValue - Partial value into which to reduce and store the result

valueToReduce - Single value to be reduced

Returns:

reduced value

reduceMerge

public PairWritable<R1,R2> reduceMerge(PairWritable<R1,R2> curValue,
                                       PairWritable<R1,R2> valueToReduce)

Description copied from interface: ReduceOperation

Add partially reduced value to current partially reduced value. Commonly, returned value should be same as curValue argument.

Specified by:

reduceMerge in interface ReduceOperation<org.apache.commons.lang3.tuple.Pair<S1,S2>,PairWritable<R1 extends org.apache.hadoop.io.Writable,R2 extends org.apache.hadoop.io.Writable>>

Parameters:

curValue - Partial value into which to reduce and store the result

valueToReduce - Partial value to be reduced

Returns:

reduced value

write

public void write(DataOutput out)
           throws IOException

Specified by:

write in interface org.apache.hadoop.io.Writable

Throws:

IOException

readFields

public void readFields(DataInput in)
                throws IOException

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Throws:

IOException