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//******************************************************************************
//
// File: CommRequest.java
// Package: edu.rit.pj
// Unit: Class edu.rit.pj.CommRequest
//
// This Java source file is copyright (C) 2007 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************
package edu.rit.pj;
import edu.rit.mp.IORequest;
import java.io.IOException;
/**
* Class CommRequest provides an object for doing a non-blocking message passing
* operation in a PJ cluster parallel program. A non-blocking message passing
* operation in class {@linkplain Comm} immediately returns a CommRequest object
* while performing the message passing operation in a separate thread. This
* allows the calling thread to do other work while the message passing
* operation is in progress. When the calling thread needs to wait for the
* message passing operation to finish, the calling thread calls the CommRequest
* object's <TT>waitForFinish()</TT> method.
*
* @author Alan Kaminsky
* @version 18-Sep-2007
*/
public class CommRequest
{
// Hidden data members.
IORequest mySendRequest;
IORequest myRecvRequest;
// Exported constructors.
/**
* Construct a new CommRequest object.
*/
public CommRequest()
{
}
// Exported operations.
/**
* Determine if the message passing operation associated with this
* CommRequest object has finished.
* <P>
* <I>Note:</I> If the <TT>isFinished()</TT> method is called on a
* newly-created CommRequest object that has not been passed to or returned
* from a communicator's non-blocking send or receive method, the
* <TT>isFinished()</TT> method immediately returns true.
*
* @return False if the message passing operation has not finished, true if
* the message passing operation has finished successfully.
*
* @exception IOException
* Thrown if the message passing operation has finished and an I/O error
* occurred.
*/
public boolean isFinished()
throws IOException
{
return
(mySendRequest == null || mySendRequest.isFinished()) &&
(myRecvRequest == null || myRecvRequest.isFinished());
}
/**
* Wait for the message passing operation associated with this CommRequest
* object to finish. If the message passing operation involved a receive, a
* {@linkplain CommStatus} object is returned giving the results of the
* receive, otherwise null is returned.
* <P>
* For a receive operation, the returned status object gives the actual rank
* of the process that sent the message, the actual message tag that was
* received, and the actual number of data items in the message. If the
* actual number of data items in the message is less than the length of the
* receive buffer, nothing is stored into the extra data items at the end of
* the buffer. If the actual number of data items in the message is greater
* than the length of the receive buffer, the extra data items at the end of
* the message are discarded.
* <P>
* <I>Note:</I> If the <TT>waitForFinish()</TT> method is called on a
* newly-created CommRequest object that has not been passed to or returned
* from a communicator's non-blocking send or receive method, the
* <TT>waitForFinish()</TT> method immediately returns null.
*
* @return Status object for a receive operation, otherwise null.
*
* @exception IOException
* Thrown if an I/O error occurred.
*/
public CommStatus waitForFinish()
throws IOException
{
if (mySendRequest != null)
{
mySendRequest.waitForFinish();
}
if (myRecvRequest != null)
{
edu.rit.mp.Status status = myRecvRequest.waitForFinish();
return new CommStatus
(Comm.getFarRank (status.channel),
status.tag,
status.length);
}
else
{
return null;
}
}
}
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