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//******************************************************************************
//
// File: ObjectOp.java
// Package: edu.rit.pj.reduction
// Unit: Class edu.rit.pj.reduction.ObjectOp
//
// This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************
package edu.rit.pj.reduction;
/**
* Class ObjectOp is the abstract base class for a binary operation on object
* values, used to do reduction in a parallel program.
* <P>
* When classes in the Parallel Java Library call the <TT>op(x,y)</TT> method
* during a reduction operation, the <TT>x</TT> argument is the value of the
* reduction variable, and the <TT>y</TT> argument is the value to be combined
* with the reduction variable. The value returned by the <TT>op(x,y)</TT>
* method is stored back into the reduction variable.
* <P>
* The <TT>op(x,y)</TT> method in any subclass of class ObjectOp must obey the
* following requirements, which are assumed by classes in the Parallel Java
* Library:
* <UL>
* <LI>
* If as a result of the binary operation the state of the reduction variable
* will not change, the <TT>op(x,y)</TT> method must return <TT>x</TT>.
* <P><LI>
* If as a result of the binary operation the state of the reduction variable
* will change, the <TT>op(x,y)</TT> method must return a newly created object
* containing the desired state.
* <P><LI>
* The <TT>op(x,y)</TT> method must neither change the state of <TT>x</TT> nor
* change the state of <TT>y</TT>; that is, the <TT>op(x,y)</TT> method must
* have no side effects.
* </UL>
*
* @param <T> Object data type.
*
* @author Alan Kaminsky
* @version 30-Mar-2008
*/
public abstract class ObjectOp<T>
extends Op
{
// Hidden constructors.
/**
* Construct a new object binary operation.
*/
protected ObjectOp()
{
super();
}
// Exported operations.
/**
* Perform this binary operation.
*
* @param x First argument.
* @param y Second argument.
*
* @return (<TT>x</TT> <I>op</I> <TT>y</TT>), where <I>op</I> stands for
* this binary operation.
*/
public abstract T op
(T x,
T y);
}
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