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1   //******************************************************************************
2   //
3   // File:    SharedFloatArrayBuf.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.SharedFloatArrayBuf
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.mp.FloatBuf;
46  import edu.rit.pj.reduction.FloatOp;
47  import edu.rit.pj.reduction.Op;
48  import edu.rit.pj.reduction.SharedFloatArray;
49  import edu.rit.util.Range;
50  
51  /**
52   * Class SharedFloatArrayBuf provides a buffer for a multiple thread safe array
53   * of float items sent or received using the Message Protocol (MP). The array
54   * element stride may be 1 or greater than 1. While an instance of class
55   * SharedFloatArrayBuf may be constructed directly, normally you will use a
56   * factory method in class {@linkplain edu.rit.mp.FloatBuf
57   * FloatBuf}. See that class for further information.
58   *
59   * @author Alan Kaminsky
60   * @version 26-Oct-2007
61   */
62  public class SharedFloatArrayBuf
63          extends FloatBuf {
64  
65  // Hidden data members.
66      SharedFloatArray myArray;
67      Range myRange;
68      int myArrayOffset;
69      int myStride;
70  
71  // Exported constructors.
72      /**
73       * Construct a new shared float array buffer.
74       *
75       * @param theArray Shared array.
76       * @param theRange Range of array elements to include in the buffer.
77       */
78      public SharedFloatArrayBuf(SharedFloatArray theArray,
79              Range theRange) {
80          super(theRange.length());
81          myArray = theArray;
82          myRange = theRange;
83          myArrayOffset = theRange.lb();
84          myStride = theRange.stride();
85      }
86  
87  // Exported operations.
88      /**
89       * {@inheritDoc}
90       *
91       * Obtain the given item from this buffer.
92       * <P>
93       * The <code>get()</code> method must not block the calling thread; if it does,
94       * all message I/O in MP will be blocked.
95       */
96      public float get(int i) {
97          return myArray.get(myArrayOffset + i * myStride);
98      }
99  
100     /**
101      * {@inheritDoc}
102      *
103      * Store the given item in this buffer.
104      * <P>
105      * The <code>put()</code> method must not block the calling thread; if it does,
106      * all message I/O in MP will be blocked.
107      */
108     public void put(int i,
109             float item) {
110         myArray.set(myArrayOffset + i * myStride, item);
111     }
112 
113     /**
114      * {@inheritDoc}
115      *
116      * Create a buffer for performing parallel reduction using the given binary
117      * operation. The results of the reduction are placed into this buffer.
118      * @exception ClassCastException (unchecked exception) Thrown if this
119      * buffer's element data type and the given binary operation's argument data
120      * type are not the same.
121      */
122     public Buf getReductionBuf(Op op) {
123         return new SharedFloatArrayReductionBuf(myArray, myRange, (FloatOp) op);
124     }
125 
126 // Hidden operations.
127     /**
128      * {@inheritDoc}
129      *
130      * Send as many items as possible from this buffer to the given byte buffer.
131      * <P>
132      * The <code>sendItems()</code> method must not block the calling thread; if it
133      * does, all message I/O in MP will be blocked.
134      */
135     protected int sendItems(int i,
136             ByteBuffer buffer) {
137         int index = i;
138         int off = myArrayOffset + i * myStride;
139         while (index < myLength && buffer.remaining() >= 4) {
140             buffer.putFloat(myArray.get(off));
141             ++index;
142             off += myStride;
143         }
144         return index - i;
145     }
146 
147     /**
148      * {@inheritDoc}
149      *
150      * Receive as many items as possible from the given byte buffer to this
151      * buffer.
152      * <P>
153      * The <code>receiveItems()</code> method must not block the calling thread; if
154      * it does, all message I/O in MP will be blocked.
155      */
156     protected int receiveItems(int i,
157             int num,
158             ByteBuffer buffer) {
159         int index = i;
160         int off = myArrayOffset + i * myStride;
161         int max = Math.min(i + num, myLength);
162         while (index < max && buffer.remaining() >= 4) {
163             myArray.set(off, buffer.getFloat());
164             ++index;
165             off += myStride;
166         }
167         return index - i;
168     }
169 
170 }