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 }