1 //****************************************************************************** 2 // 3 // File: ObjectOp.java 4 // Package: edu.rit.pj.reduction 5 // Unit: Class edu.rit.pj.reduction.ObjectOp 6 // 7 // This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights 8 // reserved. For further information, contact the author, Alan Kaminsky, at 9 // ark@cs.rit.edu. 10 // 11 // This Java source file is part of the Parallel Java Library ("PJ"). PJ is free 12 // software; you can redistribute it and/or modify it under the terms of the GNU 13 // General Public License as published by the Free Software Foundation; either 14 // version 3 of the License, or (at your option) any later version. 15 // 16 // PJ is distributed in the hope that it will be useful, but WITHOUT ANY 17 // WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR 18 // A PARTICULAR PURPOSE. See the GNU General Public License for more details. 19 // 20 // Linking this library statically or dynamically with other modules is making a 21 // combined work based on this library. Thus, the terms and conditions of the GNU 22 // General Public License cover the whole combination. 23 // 24 // As a special exception, the copyright holders of this library give you 25 // permission to link this library with independent modules to produce an 26 // executable, regardless of the license terms of these independent modules, and 27 // to copy and distribute the resulting executable under terms of your choice, 28 // provided that you also meet, for each linked independent module, the terms 29 // and conditions of the license of that module. An independent module is a module 30 // which is not derived from or based on this library. If you modify this library, 31 // you may extend this exception to your version of the library, but you are not 32 // obligated to do so. If you do not wish to do so, delete this exception 33 // statement from your version. 34 // 35 // A copy of the GNU General Public License is provided in the file gpl.txt. You 36 // may also obtain a copy of the GNU General Public License on the World Wide 37 // Web at http://www.gnu.org/licenses/gpl.html. 38 // 39 //****************************************************************************** 40 package edu.rit.pj.reduction; 41 42 /** 43 * Class ObjectOp is the abstract base class for a binary operation on object 44 * values, used to do reduction in a parallel program. 45 * <P> 46 * When classes in the Parallel Java Library call the <code>op(x,y)</code> method 47 * during a reduction operation, the <code>x</code> argument is the value of the 48 * reduction variable, and the <code>y</code> argument is the value to be combined 49 * with the reduction variable. The value returned by the <code>op(x,y)</code> 50 * method is stored back into the reduction variable. 51 * <P> 52 * The <code>op(x,y)</code> method in any subclass of class ObjectOp must obey the 53 * following requirements, which are assumed by classes in the Parallel Java 54 * Library: 55 * <UL> 56 * <LI> 57 * If as a result of the binary operation the state of the reduction variable 58 * will not change, the <code>op(x,y)</code> method must return <code>x</code>. 59 * 60 * <LI> 61 * If as a result of the binary operation the state of the reduction variable 62 * will change, the <code>op(x,y)</code> method must return a newly created object 63 * containing the desired state. 64 * 65 * <LI> 66 * The <code>op(x,y)</code> method must neither change the state of <code>x</code> nor 67 * change the state of <code>y</code>; that is, the <code>op(x,y)</code> method must 68 * have no side effects. 69 * </UL> 70 * 71 * @param <T> Object data type. 72 * @author Alan Kaminsky 73 * @version 30-Mar-2008 74 */ 75 public abstract class ObjectOp<T> 76 extends Op { 77 78 // Hidden constructors. 79 /** 80 * Construct a new object binary operation. 81 */ 82 protected ObjectOp() { 83 super(); 84 } 85 86 // Exported operations. 87 /** 88 * Perform this binary operation. 89 * 90 * @param x First argument. 91 * @param y Second argument. 92 * @return (<code>x</code> <I>op</I> <code>y</code>), where <I>op</I> stands for 93 * this binary operation. 94 */ 95 public abstract T op(T x, 96 T y); 97 98 }