org.apache.giraph.block_app.framework.api

Interface CreateReducersApi

All Superinterfaces:

BlockConfApi

All Known Implementing Classes:

CreateReducersApiWrapper

public interface CreateReducersApi
extends BlockConfApi

Api for creating reducer handles.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	CreateReducersApi.CreateReducerFunctionApi Function that creates a reducer - abstracting away whether it is local or global reducer

Method Summary

Modifier and Type	Method and Description
<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R>	createGlobalReducer(ReduceOperation<S,R> reduceOp) Create global reducer, returning a handle to it.
<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R>	createGlobalReducer(ReduceOperation<S,R> reduceOp, R globalInitialValue) Create global reducer, returning a handle to it.
<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R>	createLocalReducer(ReduceOperation<S,R> reduceOp) Create local reducer, returning a handle to it.
<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R>	createLocalReducer(ReduceOperation<S,R> reduceOp, R globalInitialValue) Create local reducer, returning a handle to it.

Methods inherited from interface org.apache.giraph.block_app.framework.api.BlockConfApi

getConf

Method Detail

createLocalReducer

<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R> createLocalReducer(ReduceOperation<S,R> reduceOp)

Create local reducer, returning a handle to it. Local reducer means that each worker thread has it's own local partially reduced value, which are at the end reduced all together. Preferable, unless it cannot be used, because all copies of the object do not fit the memory.

createLocalReducer

<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R> createLocalReducer(ReduceOperation<S,R> reduceOp,
                                                                                  R globalInitialValue)

Create local reducer, returning a handle to it. Local reducer means that each worker thread has it's own local partially reduced value, which are at the end reduced all together. Preferable, unless it cannot be used, because all copies of the object do not fit the memory.

createGlobalReducer

<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R> createGlobalReducer(ReduceOperation<S,R> reduceOp)

Create global reducer, returning a handle to it. Global reducer means that there is only one value for each worker, and each call to reduce will have to obtain a global lock, and incur synchronization costs. Use only when objects are so large, that having many copies cannot fit into memory.

createGlobalReducer

<S,R extends org.apache.hadoop.io.Writable> ReducerHandle<S,R> createGlobalReducer(ReduceOperation<S,R> reduceOp,
                                                                                   R globalInitialValue)

Create global reducer, returning a handle to it. Global reducer means that there is only one value for each worker, and each call to reduce will have to obtain a global lock, and incur synchronization costs. Use only when objects are so large, that having many copies cannot fit into memory.