1 //******************************************************************************
2 //
3 // File: SharedByteArrayReductionBuf.java
4 // Package: edu.rit.mp.buf
5 // Unit: Class edu.rit.mp.buf.SharedByteArrayReductionBuf
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.SharedByteArray;
48 import edu.rit.util.Range;
49
50 /**
51 * Class SharedByteArrayReductionBuf provides a reduction buffer for class
52 * {@linkplain SharedByteArrayBuf}.
53 *
54 * @author Alan Kaminsky
55 * @version 26-Oct-2007
56 */
57 class SharedByteArrayReductionBuf
58 extends SharedByteArrayBuf {
59
60 // Hidden data members.
61 ByteOp myOp;
62
63 // Exported constructors.
64 /**
65 * Construct a new shared byte array reduction buffer.
66 *
67 * @param theArray Shared array.
68 * @param theRange Range of array elements to include in the buffer.
69 * @param op Binary operation.
70 * @exception NullPointerException (unchecked exception) Thrown if
71 * <code>op</code> is null.
72 */
73 public SharedByteArrayReductionBuf(SharedByteArray theArray,
74 Range theRange,
75 ByteOp op) {
76 super(theArray, theRange);
77 if (op == null) {
78 throw new NullPointerException("SharedByteArrayReductionBuf(): op is null");
79 }
80 myOp = op;
81 }
82
83 // Exported operations.
84 /**
85 * {@inheritDoc}
86 *
87 * Store the given item in this buffer.
88 * <P>
89 * The <code>put()</code> method must not block the calling thread; if it does,
90 * all message I/O in MP will be blocked.
91 */
92 public void put(int i,
93 byte item) {
94 myArray.reduce(myArrayOffset + i * myStride, item, myOp);
95 }
96
97 /**
98 * {@inheritDoc}
99 *
100 * Create a buffer for performing parallel reduction using the given binary
101 * operation. The results of the reduction are placed into this buffer.
102 * @exception ClassCastException (unchecked exception) Thrown if this
103 * buffer's element data type and the given binary operation's argument data
104 * type are not the same.
105 */
106 public Buf getReductionBuf(Op op) {
107 throw new UnsupportedOperationException();
108 }
109
110 // Hidden operations.
111 /**
112 * {@inheritDoc}
113 *
114 * Receive as many items as possible from the given byte buffer to this
115 * buffer.
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 int index = i;
124 int off = myArrayOffset + i * myStride;
125 int max = Math.min(i + num, myLength);
126 while (index < max && buffer.remaining() >= 1) {
127 myArray.reduce(off, buffer.get(), myOp);
128 ++index;
129 off += myStride;
130 }
131 return index - i;
132 }
133
134 }