1 //******************************************************************************
2 //
3 // File: SharedByteReductionBuf.java
4 // Package: edu.rit.mp.buf
5 // Unit: Class edu.rit.mp.buf.SharedByteReductionBuf
6 //
7 // This Java source file is copyright (C) 2007 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.mp.buf;
41
42 import java.nio.ByteBuffer;
43
44 import edu.rit.mp.Buf;
45 import edu.rit.pj.reduction.ByteOp;
46 import edu.rit.pj.reduction.Op;
47 import edu.rit.pj.reduction.SharedByte;
48
49 /**
50 * Class SharedByteReductionBuf provides a reduction buffer for class
51 * {@linkplain SharedByteBuf}.
52 *
53 * @author Alan Kaminsky
54 * @version 26-Oct-2007
55 */
56 class SharedByteReductionBuf
57 extends SharedByteBuf {
58
59 // Hidden data members.
60 ByteOp myOp;
61
62 // Exported constructors.
63 /**
64 * Construct a new byte item reduction buffer.
65 *
66 * @param item SharedByte object that wraps the item.
67 * @param op Binary operation.
68 * @exception NullPointerException (unchecked exception) Thrown if
69 * <code>op</code> is null.
70 */
71 public SharedByteReductionBuf(SharedByte item,
72 ByteOp op) {
73 super(item);
74 if (op == null) {
75 throw new NullPointerException("SharedByteReductionBuf(): op is null");
76 }
77 myOp = op;
78 }
79
80 // Exported operations.
81 /**
82 * {@inheritDoc}
83 *
84 * Store the given item in this buffer. The item at index <code>i</code> in this
85 * buffer is combined with the given <code>item</code> using the binary
86 * operation.
87 * <P>
88 * The <code>put()</code> method must not block the calling thread; if it does,
89 * all message I/O in MP will be blocked.
90 */
91 public void put(int i,
92 byte item) {
93 myItem.reduce(item, myOp);
94 }
95
96 /**
97 * {@inheritDoc}
98 *
99 * Create a buffer for performing parallel reduction using the given binary
100 * operation. The results of the reduction are placed into this buffer.
101 * @exception ClassCastException (unchecked exception) Thrown if this
102 * buffer's element data type and the given binary operation's argument data
103 * type are not the same.
104 */
105 public Buf getReductionBuf(Op op) {
106 throw new UnsupportedOperationException();
107 }
108
109 // Hidden operations.
110 /**
111 * {@inheritDoc}
112 *
113 * Receive as many items as possible from the given byte buffer to this
114 * buffer. As the items are received, they are combined with the items in
115 * this buffer using the binary operation.
116 * <P>
117 * The <code>receiveItems()</code> method must not block the calling thread; if
118 * it does, all message I/O in MP will be blocked.
119 */
120 protected int receiveItems(int i,
121 int num,
122 ByteBuffer buffer) {
123 if (num >= 1 && buffer.remaining() >= 1) {
124 myItem.reduce(buffer.get(), myOp);
125 return 1;
126 } else {
127 return 0;
128 }
129 }
130
131 }