View Javadoc
1   //******************************************************************************
2   //
3   // File:    SharedByteArrayReductionBuf_1.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.SharedByteArrayReductionBuf_1
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_1 provides a reduction buffer for class
52   * {@linkplain SharedByteArrayBuf_1}.
53   *
54   * @author Alan Kaminsky
55   * @version 26-Oct-2007
56   */
57  class SharedByteArrayReductionBuf_1
58          extends SharedByteArrayBuf_1 {
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. The
69       * stride is assumed to be 1.
70       * @param op Binary operation.
71       * @exception NullPointerException (unchecked exception) Thrown if
72       * <code>op</code> is null.
73       */
74      public SharedByteArrayReductionBuf_1(SharedByteArray theArray,
75              Range theRange,
76              ByteOp op) {
77          super(theArray, theRange);
78          if (op == null) {
79              throw new NullPointerException("SharedByteArrayReductionBuf_1(): op is null");
80          }
81          myOp = op;
82      }
83  
84  // Exported operations.
85      /**
86       * {@inheritDoc}
87       *
88       * Store the given item in this buffer.
89       * <P>
90       * The <code>put()</code> method must not block the calling thread; if it does,
91       * all message I/O in MP will be blocked.
92       */
93      public void put(int i,
94              byte item) {
95          myArray.reduce(myArrayOffset + i, item, myOp);
96      }
97  
98      /**
99       * {@inheritDoc}
100      *
101      * Create a buffer for performing parallel reduction using the given binary
102      * operation. The results of the reduction are placed into this buffer.
103      * @exception ClassCastException (unchecked exception) Thrown if this
104      * buffer's element data type and the given binary operation's argument data
105      * type are not the same.
106      */
107     public Buf getReductionBuf(Op op) {
108         throw new UnsupportedOperationException();
109     }
110 
111 // Hidden operations.
112     /**
113      * {@inheritDoc}
114      *
115      * Receive as many items as possible from the given byte buffer to this
116      * buffer.
117      * <P>
118      * The <code>receiveItems()</code> method must not block the calling thread; if
119      * it does, all message I/O in MP will be blocked.
120      */
121     protected int receiveItems(int i,
122             int num,
123             ByteBuffer buffer) {
124         int index = i;
125         int off = myArrayOffset + i;
126         int max = Math.min(i + num, myLength);
127         while (index < max && buffer.remaining() >= 1) {
128             myArray.reduce(off, buffer.get(), myOp);
129             ++index;
130             ++off;
131         }
132         return index - i;
133     }
134 
135 }