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1   //******************************************************************************
2   //
3   // File:    LongArrayReductionBuf.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.LongArrayReductionBuf
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.LongBuf;
46  import edu.rit.pj.reduction.LongOp;
47  import edu.rit.pj.reduction.Op;
48  import edu.rit.pj.reduction.ReduceArrays;
49  import edu.rit.util.Range;
50  
51  /**
52   * Class LongArrayReductionBuf provides a reduction buffer for class
53   * {@linkplain LongArrayBuf}.
54   *
55   * @author Alan Kaminsky
56   * @version 25-Oct-2007
57   */
58  class LongArrayReductionBuf
59          extends LongArrayBuf {
60  
61  // Hidden data members.
62      LongOp myOp;
63  
64  // Exported constructors.
65      /**
66       * Construct a new long array reduction buffer.
67       *
68       * @param theArray Array.
69       * @param theRange Range of array elements to include in the buffer.
70       * @param op Binary operation.
71       * @exception NullPointerException (unchecked exception) Thrown if
72       * <code>op</code> is null.
73       */
74      public LongArrayReductionBuf(long[] theArray,
75              Range theRange,
76              LongOp op) {
77          super(theArray, theRange);
78          if (op == null) {
79              throw new NullPointerException("LongArrayReductionBuf(): 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              long item) {
95          int off = myArrayOffset + i * myStride;
96          myArray[off] = myOp.op(myArray[off], item);
97      }
98  
99      /**
100      * {@inheritDoc}
101      *
102      * Copy items from the given buffer to this buffer. The number of items
103      * copied is this buffer's length or <code>theSrc</code>'s length, whichever is
104      * smaller. If <code>theSrc</code> is this buffer, the <code>copy()</code> method
105      * does nothing.
106      * @exception ClassCastException (unchecked exception) Thrown if
107      * <code>theSrc</code>'s item data type is not the same as this buffer's item
108      * data type.
109      */
110     public void copy(Buf theSrc) {
111         if (theSrc == this) {
112         } else if (theSrc instanceof LongArrayBuf) {
113             LongArrayBuf src = (LongArrayBuf) theSrc;
114             ReduceArrays.reduce(src.myArray, src.myRange, this.myArray, this.myRange, myOp);
115         } else {
116             LongBuf.defaultCopy((LongBuf) theSrc, this);
117         }
118     }
119 
120     /**
121      * {@inheritDoc}
122      *
123      * Create a buffer for performing parallel reduction using the given binary
124      * operation. The results of the reduction are placed into this buffer.
125      * @exception ClassCastException (unchecked exception) Thrown if this
126      * buffer's element data type and the given binary operation's argument data
127      * type are not the same.
128      */
129     public Buf getReductionBuf(Op op) {
130         throw new UnsupportedOperationException();
131     }
132 
133 // Hidden operations.
134     /**
135      * {@inheritDoc}
136      *
137      * Receive as many items as possible from the given byte buffer to this
138      * buffer.
139      * <P>
140      * The <code>receiveItems()</code> method must not block the calling thread; if
141      * it does, all message I/O in MP will be blocked.
142      */
143     protected int receiveItems(int i,
144             int num,
145             ByteBuffer buffer) {
146         int index = i;
147         int off = myArrayOffset + i * myStride;
148         int max = Math.min(i + num, myLength);
149         while (index < max && buffer.remaining() >= 8) {
150             myArray[off] = myOp.op(myArray[off], buffer.getLong());
151             ++index;
152             off += myStride;
153         }
154         return index - i;
155     }
156 
157 }