156 lines
5.6 KiB
Java
156 lines
5.6 KiB
Java
//******************************************************************************
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//
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// File: Customizer.java
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// Package: edu.rit.pjmr
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// Unit: Class edu.rit.pjmr.Customizer
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//
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// This Java source file is copyright (C) 2013 by Alan Kaminsky. All rights
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// reserved. For further information, contact the author, Alan Kaminsky, at
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// ark@cs.rit.edu.
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//
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// This Java source file is part of the Parallel Java 2 Library ("PJ2"). PJ2 is
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// free software; you can redistribute it and/or modify it under the terms of
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// the GNU General Public License as published by the Free Software Foundation;
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// either version 3 of the License, or (at your option) any later version.
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//
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// PJ2 is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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//
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// A copy of the GNU General Public License is provided in the file gpl.txt. You
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// may also obtain a copy of the GNU General Public License on the World Wide
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// Web at http://www.gnu.org/licenses/gpl.html.
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//
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//******************************************************************************
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package edu.rit.pjmr;
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import edu.rit.pj2.Vbl;
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/**
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* Class Customizer is the base class for a customizer in the Parallel Java Map
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* Reduce Framework. See class {@linkplain PjmrJob} for further information
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* about configuring customizers as part of a PJMR job.
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* <P>
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* A {@linkplain MapperTask} calls a customizer's methods as follows:
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* <OL TYPE=1>
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* <P><LI>
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* The mapper task calls the customizer's {@link #start(String[],Combiner)
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* start()} method, in a single thread, before running the {@linkplain Mapper}s.
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* The arguments are the customizer's argument strings if any, and the
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* {@linkplain Combiner} that will accumulate the mappers' results. The
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* <TT>start()</TT> method may initialize the customizer based on the argument
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* strings. The <TT>start()</TT> method may do preprocessing operations on the
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* combiner.
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* <P><LI>
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* The mapper task calls the customizer's {@link #finish(Combiner) finish()}
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* method, in a single thread, after all the {@linkplain Mapper}s have finished.
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* The argument is the {@linkplain Combiner}. The <TT>finish()</TT> method may
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* do postprocessing operations on the combiner.
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* </OL>
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* <P>
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* A {@linkplain ReducerTask} calls a customizer's methods as follows:
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* <OL TYPE=1>
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* <P><LI>
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* The reducer task calls the customizer's {@link #start(String[],Combiner)
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* start()} method, in a single thread, before running the {@linkplain
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* Reducer}s. The arguments are the customizer's argument strings if any, and
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* the {@linkplain Combiner} that contains all the mappers' results. The
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* <TT>start()</TT> method may initialize the customizer based on the argument
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* strings. The <TT>start()</TT> method may do preprocessing operations on the
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* combiner.
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* <P><LI>
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* If the customizer's {@link #comesBefore(Object,Vbl,Object,Vbl) comesBefore()}
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* method has been overridden, the reducer task sorts the combiner's (key,
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* value) pairs, in a single thread, before running the {@linkplain Reducer}s.
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* The reducer task calls the customizer's {@link
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* #comesBefore(Object,Vbl,Object,Vbl) comesBefore()} method to determine the
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* ordering of the pairs. The reducer task passes the pairs to the {@linkplain
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* Reducer}s in the resulting sorted order. If the customizer's {@link
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* #comesBefore(Object,Vbl,Object,Vbl) comesBefore()} method has not been
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* overridden, the reducer task does not sort the combiner's pairs, and the
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* reducer task passes the pairs to the {@linkplain Reducer}s in an unspecified
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* order.
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* <P><LI>
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* The reducer task calls the customizer's {@link #finish(Combiner) finish()}
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* method, in a single thread, after all the {@linkplain Reducer}s have
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* finished. The argument is the {@linkplain Combiner}. The <TT>finish()</TT>
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* method may do postprocessing operations on the combiner.
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* </OL>
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*
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* @param <K> Mapper output key data type.
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* @param <V> Mapper output value data type; must implement interface
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* {@linkplain edu.rit.pj2.Vbl Vbl}.
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*
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* @author Alan Kaminsky
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* @version 28-Nov-2013
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*/
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public class Customizer <K,V extends Vbl>
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{
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// Exported constructors.
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/**
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* Construct a new customizer.
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*/
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public Customizer()
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{
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}
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// Exported operations.
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/**
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* Start this customizer.
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* <P>
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* The base class <TT>start()</TT> method does nothing. A subclass may
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* override the <TT>start()</TT> method to do something.
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*
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* @param args Array of zero or more argument strings.
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* @param combiner Combiner.
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*/
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public void start
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(String[] args,
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Combiner<K,V> combiner)
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{
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}
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/**
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* Determine if the first (key, value) pair comes before the second (key,
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* value) pair in the desired sorted order.
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* <P>
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* The Customizer base class does not sort the pairs. A subclass may
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* override the <TT>comesBefore()</TT> method to sort the pairs into the
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* desired order.
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*
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* @param key_1 Key from first pair.
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* @param value_1 Value from first pair.
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* @param key_2 Key from second pair.
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* @param value_2 Value from second pair.
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*
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* @return True if the first pair comes before the second pair, false
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* otherwise.
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*/
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public boolean comesBefore
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(K key_1,
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V value_1,
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K key_2,
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V value_2)
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{
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throw new UnsupportedOperationException();
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}
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/**
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* Finish this customizer.
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* <P>
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* The base class <TT>finish()</TT> method does nothing. A subclass may
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* override the <TT>finish()</TT> method to do something.
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*
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* @param combiner Combiner.
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*/
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public void finish
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(Combiner<K,V> combiner)
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{
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}
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}
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