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1   //******************************************************************************
2   //
3   // File:    ByteArrayReductionBuf_1.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.ByteArrayReductionBuf_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
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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.mp.ByteBuf;
46  import edu.rit.pj.reduction.ByteOp;
47  import edu.rit.pj.reduction.Op;
48  import edu.rit.pj.reduction.ReduceArrays;
49  import edu.rit.util.Range;
50  
51  /**
52   * Class ByteArrayReductionBuf_1 provides a reduction buffer for class
53   * {@linkplain ByteArrayBuf_1}.
54   *
55   * @author Alan Kaminsky
56   * @version 25-Oct-2007
57   */
58  class ByteArrayReductionBuf_1
59          extends ByteArrayBuf_1 {
60  
61  // Hidden data members.
62      ByteOp myOp;
63  
64  // Exported constructors.
65      /**
66       * Construct a new byte array reduction buffer.
67       *
68       * @param theArray Array.
69       * @param theRange Range of array elements to include in the buffer. The
70       * stride is assumed to be 1.
71       * @param op Binary operation.
72       * @exception NullPointerException (unchecked exception) Thrown if
73       * <code>op</code> is null.
74       */
75      public ByteArrayReductionBuf_1(byte[] theArray,
76              Range theRange,
77              ByteOp op) {
78          super(theArray, theRange);
79          if (op == null) {
80              throw new NullPointerException("ByteArrayReductionBuf_1(): op is null");
81          }
82          myOp = op;
83      }
84  
85  // Exported operations.
86      /**
87       * {@inheritDoc}
88       *
89       * Store the given item in this buffer.
90       * <P>
91       * The <code>put()</code> method must not block the calling thread; if it does,
92       * all message I/O in MP will be blocked.
93       */
94      public void put(int i,
95              byte item) {
96          int off = myArrayOffset + i;
97          myArray[off] = myOp.op(myArray[off], item);
98      }
99  
100     /**
101      * {@inheritDoc}
102      *
103      * Copy items from the given buffer to this buffer. The number of items
104      * copied is this buffer's length or <code>theSrc</code>'s length, whichever is
105      * smaller. If <code>theSrc</code> is this buffer, the <code>copy()</code> method
106      * does nothing.
107      * @exception ClassCastException (unchecked exception) Thrown if
108      * <code>theSrc</code>'s item data type is not the same as this buffer's item
109      * data type.
110      */
111     public void copy(Buf theSrc) {
112         if (theSrc == this) {
113         } else if (theSrc instanceof ByteArrayBuf) {
114             ByteArrayBuf src = (ByteArrayBuf) theSrc;
115             ReduceArrays.reduce(src.myArray, src.myRange, this.myArray, this.myRange, myOp);
116         } else {
117             ByteBuf.defaultCopy((ByteBuf) theSrc, this);
118         }
119     }
120 
121     /**
122      * {@inheritDoc}
123      *
124      * Create a buffer for performing parallel reduction using the given binary
125      * operation. The results of the reduction are placed into this buffer.
126      * @exception ClassCastException (unchecked exception) Thrown if this
127      * buffer's element data type and the given binary operation's argument data
128      * type are not the same.
129      */
130     public Buf getReductionBuf(Op op) {
131         throw new UnsupportedOperationException();
132     }
133 
134 // Hidden operations.
135     /**
136      * {@inheritDoc}
137      *
138      * Receive as many items as possible from the given byte buffer to this
139      * buffer.
140      * <P>
141      * The <code>receiveItems()</code> method must not block the calling thread; if
142      * it does, all message I/O in MP will be blocked.
143      */
144     protected int receiveItems(int i,
145             int num,
146             ByteBuffer buffer) {
147         int index = i;
148         int off = myArrayOffset + i;
149         int max = Math.min(i + num, myLength);
150         while (index < max && buffer.remaining() >= 1) {
151             myArray[off] = myOp.op(myArray[off], buffer.get());
152             ++index;
153             ++off;
154         }
155         return index - i;
156     }
157 
158 }