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1   //******************************************************************************
2   //
3   // File:    ObjectItemReductionBuf.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.ObjectItemReductionBuf
6   //
7   // This Java source file is copyright (C) 2009 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
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38  //
39  //******************************************************************************
40  package edu.rit.mp.buf;
41  
42  import edu.rit.mp.Buf;
43  import edu.rit.mp.ObjectBuf;
44  import edu.rit.pj.reduction.ObjectOp;
45  import edu.rit.pj.reduction.Op;
46  
47  /**
48   * Class ObjectItemReductionBuf provides a reduction buffer for class
49   * {@linkplain ObjectItemBuf}.
50   *
51   * @param <T> Data type of the objects in the buffer.
52   *
53   * @author Alan Kaminsky
54   * @version 23-Mar-2009
55   */
56  class ObjectItemReductionBuf<T>
57          extends ObjectBuf<T> {
58  
59  // Hidden data members.
60      ObjectItemBuf<T> myBuf;
61      ObjectOp<T> myOp;
62  
63  // Exported constructors.
64      /**
65       * Construct a new object item reduction buffer.
66       *
67       * @param buf Buffer containing the item.
68       * @param op Binary operation.
69       * @exception NullPointerException (unchecked exception) Thrown if
70       * <code>op</code> is null.
71       */
72      public ObjectItemReductionBuf(ObjectItemBuf<T> buf,
73              ObjectOp<T> op) {
74          super(1);
75          if (op == null) {
76              throw new NullPointerException("ObjectItemReductionBuf(): op is null");
77          }
78          myBuf = buf;
79          myOp = op;
80      }
81  
82  // Exported operations.
83      /**
84       * {@inheritDoc}
85       *
86       * Obtain the given item from this buffer.
87       * <P>
88       * The <code>get()</code> method must not block the calling thread; if it does,
89       * all message I/O in MP will be blocked.
90       */
91      public T get(int i) {
92          return myBuf.item;
93      }
94  
95      /**
96       * Store the given item in this buffer. The item at index <code>i</code> in this
97       * buffer is combined with the given <code>item</code> using the binary
98       * operation.
99       * <P>
100      * The <code>put()</code> method must not block the calling thread; if it does,
101      * all message I/O in MP will be blocked.
102      *
103      * @param i Item index in the range 0 .. <code>length()</code>-1.
104      * @param item Item to be stored at index <code>i</code>.
105      */
106     public void put(int i, T item) {
107         myBuf.item = myOp.op(myBuf.item, item);
108         reset();
109         myBuf.reset();
110     }
111 
112     /**
113      * {@inheritDoc}
114      *
115      * Create a buffer for performing parallel reduction using the given binary
116      * operation. The results of the reduction are placed into this buffer.
117      * @exception ClassCastException (unchecked exception) Thrown if this
118      * buffer's element data type and the given binary operation's argument data
119      * type are not the same.
120      */
121     public Buf getReductionBuf(Op op) {
122         throw new UnsupportedOperationException();
123     }
124 
125 }