org.apache.giraph.block_app.reducers.array

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

java.lang.Object

org.apache.giraph.block_app.reducers.array.ArrayReduce<S,R>

Type Parameters:

S - Single value type, objects passed on workers

R - Reduced value type

All Implemented Interfaces:

ReduceOperation<org.apache.commons.lang3.tuple.Pair<PrimitiveRefs.IntRef,S>,ArrayWritable<R>>, org.apache.hadoop.io.Writable

public class ArrayReduce<S,R extends org.apache.hadoop.io.Writable>
extends Object
implements ReduceOperation<org.apache.commons.lang3.tuple.Pair<PrimitiveRefs.IntRef,S>,ArrayWritable<R>>

One reducer representing reduction of array of individual values. Elements are represented as object, and so BasicArrayReduce should be used instead when elements are primitive types.

Constructor Summary

Constructors

Constructor and Description
ArrayReduce()
ArrayReduce(int fixedSize, ReduceOperation<S,R> elementReduceOp) Create ReduceOperation that reduces arrays by reducing individual elements.

Method Summary

Modifier and Type	Method and Description
static <S,T extends org.apache.hadoop.io.Writable> ReducerArrayHandle<S,T>	createArrayHandles(int fixedSize, ReduceOperation<S,T> elementReduceOp, CreateReducersApi.CreateReducerFunctionApi createFunction) Registers one new reducer, that will reduce array of objects, by reducing individual elements using elementReduceOp.
ArrayWritable<R>	createInitialValue() Return new reduced value which is neutral to reduce operation.
void	readFields(DataInput in)
ArrayWritable<R>	reduce(ArrayWritable<R> curValue, org.apache.commons.lang3.tuple.Pair<PrimitiveRefs.IntRef,S> valueToReduce) Add a new value.
ArrayWritable<R>	reduceMerge(ArrayWritable<R> curValue, ArrayWritable<R> 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

ArrayReduce

public ArrayReduce()

ArrayReduce

public ArrayReduce(int fixedSize,
                   ReduceOperation<S,R> elementReduceOp)

Create ReduceOperation that reduces arrays by reducing individual elements.

Parameters:

fixedSize - Number of elements

elementReduceOp - ReduceOperation for individual elements

Method Detail

createArrayHandles

public static <S,T extends org.apache.hadoop.io.Writable> ReducerArrayHandle<S,T> createArrayHandles(int fixedSize,
                                                                                                     ReduceOperation<S,T> elementReduceOp,
                                                                                                     CreateReducersApi.CreateReducerFunctionApi createFunction)

Registers one new reducer, that will reduce array of objects, by reducing individual elements using elementReduceOp. This function will return ReducerArrayHandle to it, by which individual elements can be manipulated separately.

Parameters:

fixedSize - Number of elements

elementReduceOp - ReduceOperation for individual elements

createFunction - Function for creating a reducer

Returns:

Created ReducerArrayHandle

createInitialValue

public ArrayWritable<R> 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<PrimitiveRefs.IntRef,S>,ArrayWritable<R extends org.apache.hadoop.io.Writable>>

Returns:

Neutral value

reduce

public ArrayWritable<R> reduce(ArrayWritable<R> curValue,
                               org.apache.commons.lang3.tuple.Pair<PrimitiveRefs.IntRef,S> 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<PrimitiveRefs.IntRef,S>,ArrayWritable<R 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 ArrayWritable<R> reduceMerge(ArrayWritable<R> curValue,
                                    ArrayWritable<R> 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<PrimitiveRefs.IntRef,S>,ArrayWritable<R 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