1 //******************************************************************************
2 //
3 // File: CommRequest.java
4 // Package: edu.rit.pj
5 // Unit: Class edu.rit.pj.CommRequest
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.pj;
41
42 import java.io.IOException;
43
44 import edu.rit.mp.IORequest;
45
46 /**
47 * Class CommRequest provides an object for doing a non-blocking message passing
48 * operation in a PJ cluster parallel program. A non-blocking message passing
49 * operation in class {@linkplain Comm} immediately returns a CommRequest object
50 * while performing the message passing operation in a separate thread. This
51 * allows the calling thread to do other work while the message passing
52 * operation is in progress. When the calling thread needs to wait for the
53 * message passing operation to finish, the calling thread calls the CommRequest
54 * object's <code>waitForFinish()</code> method.
55 *
56 * @author Alan Kaminsky
57 * @version 18-Sep-2007
58 */
59 public class CommRequest {
60
61 // Hidden data members.
62 IORequest mySendRequest;
63 IORequest myRecvRequest;
64
65 // Exported constructors.
66 /**
67 * Construct a new CommRequest object.
68 */
69 public CommRequest() {
70 }
71
72 // Exported operations.
73 /**
74 * Determine if the message passing operation associated with this
75 * CommRequest object has finished.
76 * <P>
77 * <I>Note:</I> If the <code>isFinished()</code> method is called on a
78 * newly-created CommRequest object that has not been passed to or returned
79 * from a communicator's non-blocking send or receive method, the
80 * <code>isFinished()</code> method immediately returns true.
81 *
82 * @return False if the message passing operation has not finished, true if
83 * the message passing operation has finished successfully.
84 * @exception IOException Thrown if the message passing operation has
85 * finished and an I/O error occurred.
86 * @throws java.io.IOException if any.
87 */
88 public boolean isFinished()
89 throws IOException {
90 return (mySendRequest == null || mySendRequest.isFinished())
91 && (myRecvRequest == null || myRecvRequest.isFinished());
92 }
93
94 /**
95 * Wait for the message passing operation associated with this CommRequest
96 * object to finish. If the message passing operation involved a receive, a
97 * {@linkplain CommStatus} object is returned giving the results of the
98 * receive, otherwise null is returned.
99 * <P>
100 * For a receive operation, the returned status object gives the actual rank
101 * of the process that sent the message, the actual message tag that was
102 * received, and the actual number of data items in the message. If the
103 * actual number of data items in the message is less than the length of the
104 * receive buffer, nothing is stored into the extra data items at the end of
105 * the buffer. If the actual number of data items in the message is greater
106 * than the length of the receive buffer, the extra data items at the end of
107 * the message are discarded.
108 * <P>
109 * <I>Note:</I> If the <code>waitForFinish()</code> method is called on a
110 * newly-created CommRequest object that has not been passed to or returned
111 * from a communicator's non-blocking send or receive method, the
112 * <code>waitForFinish()</code> method immediately returns null.
113 *
114 * @return Status object for a receive operation, otherwise null.
115 * @exception IOException Thrown if an I/O error occurred.
116 * @throws java.io.IOException if any.
117 */
118 public CommStatus waitForFinish()
119 throws IOException {
120 if (mySendRequest != null) {
121 mySendRequest.waitForFinish();
122 }
123 if (myRecvRequest != null) {
124 edu.rit.mp.Status status = myRecvRequest.waitForFinish();
125 return new CommStatus(Comm.getFarRank(status.channel),
126 status.tag,
127 status.length);
128 } else {
129 return null;
130 }
131 }
132
133 }