Re: [OMPI users] Urgent Question regarding, MPI_ANY_SOURCE.

Terry Dontje Fri, 15 Jul 2011 15:06:51 -0400


On 7/15/2011 2:35 PM, Mudassar Majeed wrote:

Here is the code

    if( (is_receiver == 1) && (is_sender != 1) )
    {
        printf("\nP%d >> Receiver only ...!!", myid);
        printf("\n");
MPI_Recv(&recv_packet, 1, loadDatatype, MPI_ANY_SOURCE,MPI_TAG_LOAD, comm, &status);
        printf("\nP%d >> Received from P%d", myid, status.MPI_SOURCE);
        printf("\n");
    }
    else if( (is_sender == 1) && (is_receiver != 1) )
    {
        load_packet.rank = *id;
        load_packet.ld = load;
        printf("\nP%d >> Sender only ...!! P%d", myid, rec_rank);
        printf("\n");
MPI_Ssend(&load_packet, 1, loadDatatype, rec_rank,MPI_TAG_LOAD, comm);
    }
    else if( (is_receiver == 1) && (is_sender == 1) )
    {
        load_packet.rank = *id;
        load_packet.ld = load;
        printf("\nP%d >> Both ...!! P%d", myid, rec_rank);
        printf("\n");
MPI_Sendrecv(&load_packet, 1, loadDatatype, rec_rank,MPI_TAG_LOAD,&recv_packet, 1, loadDatatype, MPI_ANY_SOURCE, MPI_TAG_LOAD, comm,&status);
        printf("\nP%d >> Received from P%d", myid, status.MPI_SOURCE);
        printf("\n");
    }
A process can be a message sender, or receiver or both. There are 16ranks. "rec_rank" contains the rank of the receiver. It is displayedbefore the message is sent.Every sender displays this "rec_rank" and it should correctly. But onthe receiver sides, status.MPI_SOURCE is displayed (after receivingmessage), but the value
is not matching with the expected sender's rank.

Sorry, but I still don't see how you are detecting the mismatch. Iassume load_packet_rank some how relates to load_packet. But why areyou setting it to *id instead of myid? Also on the receive side I seeno place where you pull out the rank from the recv_packet to comparewith status.MPI_SOURCE.


I did not understand about kernel that you were talking about.

A "kernel" that I am talking about is a small piece of code someone canbuild and run to see the problem.

See the code is very clear and it sends the message to "rec_rank" thatwas displayed before sending the message. But on the receiver side theMPI_SOURCE comes to be wrong.This shows to me that messages on the receiving sides are captured onthe basis of MPI_ANY_SOURCE, that seems like it does not see thedestination of message while capturing it from message queue of theMPI system.
regards,
Mudassar

------------------------------------------------------------------------
*From:* Terry Dontje <terry.don...@oracle.com>
*To:* Mudassar Majeed <mudassar...@yahoo.com>
*Cc:* "us...@open-mpi.org" <us...@open-mpi.org>
*Sent:* Friday, July 15, 2011 7:10 PM
*Subject:* Re: [OMPI users] Urgent Question regarding, MPI_ANY_SOURCE.



On 7/15/2011 12:49 PM, Mudassar Majeed wrote:
Yes, processes receive messages that were not sent to them. I amreceiving the message with the following call
MPI_Recv(&recv_packet, 1, loadDatatype, MPI_ANY_SOURCE, MPI_TAG_LOAD,comm, &status);
and that was sent using the following call,

MPI_Ssend(&load_packet, 1, loadDatatype, rec_rank, MPI_TAG_LOAD, comm);
What problem it can have ?. All the parameters are correct, I haveseen them by printf. What I am thinking is that, the receive is donewith MPI_ANY_SOURCE, so the process is getting any message (from anysource). What should be done so that only that message is capturedthat had the destination as this process.
By virtue of MPI the MPI_Recv call should only return messagesdestined for that rank. What makes you think that is not happening?Can you make some sort of kernel of code that proves your theory thatyour MPI_Recv is receiving another rank's message? If you can andthen post that code maybe we'll be able to figure out what the issue is.
Right now, it seems we are at a deadlock of you claiming something ishappening that really cannot be happening. So unless we have morethan a broad description of the problem it is going to be nearlyimpossible for us to tell you what is wrong.
--td
regards,
Mudassar

Date: Fri, 15 Jul 2011 07:04:34 -0400
From: Terry Dontje <terry.don...@oracle.com<mailto:terry.don...@oracle.com>>
Subject: Re: [OMPI users] Urgent Question regarding, MPI_ANY_SOURCE.
To: us...@open-mpi.org <mailto:us...@open-mpi.org>
Message-ID: <4e201ec2....@oracle.com <mailto:4e201ec2....@oracle.com>>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"

Well MPI_Recv does give you the message that was sent specifically to
the rank calling it by any of the processes in the communicator.  If you
think the message you received should have gone to another rank then
there is a bug somewhere.  I would start by either adding debugging
printf's to your code to trace the messages.  Or narrowing down the
code to a small kernel such that you can prove to yourself that MPI is
working the way it should and if not you can show us where it is going
wrong.

--td

On 7/15/2011 6:51 AM, Mudassar Majeed wrote:
> I get the sender's rank in status.MPI_SOURCE, but it is different than
> expected. I need to receive that message which was sent to me, not any
> message.
>
> regards,
>
> Date: Fri, 15 Jul 2011 06:33:41 -0400
> From: Terry Dontje <terry.don...@oracle.com<mailto:terry.don...@oracle.com>
> <mailto:terry.don...@oracle.com <mailto:terry.don...@oracle.com>>>
> Subject: Re: [OMPI users] Urgent Question regarding, MPI_ANY_SOURCE.
> To: us...@open-mpi.org <mailto:us...@open-mpi.org><mailto:us...@open-mpi.org <mailto:us...@open-mpi.org>>> Message-ID: <4e201785.6010...@oracle.com<mailto:4e201785.6010...@oracle.com>> <mailto:4e201785.6010...@oracle.com<mailto:4e201785.6010...@oracle.com>>>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> Mudassar,
>
> You can do what you are asking.  The receiver uses MPI_ANY_SOURCE for
> the source rank value and when you receive a message the
> status.MPI_SOURCE will contain the rank of the actual sender not the
> receiver's rank.  If you are not seeing that then there is a bug
> somewhere.
>
> --td
>
> On 7/14/2011 9:54 PM, Mudassar Majeed wrote:
> > Friend,
> >              I can not specify the rank of the sender. Because only
> > the sender knows to which receiver the message is to be sent. The
> > receiver does not know from which sender the message will come. I am
> > trying to do a research work on load balancing in MPI application
> > where load is redistributed, so in that I require a receiver to
> > receive a load value from a sender that it does not know. On theother
> > hand, the sender actually calculates, to which receiver this load
> > value should be sent. So for this, I want sender to send a message
> > containing the load to a receiver, but receiver does not know from
> > which sender the message will come. See, it is like send receiver in
> > DATAGRAM sockets. The receiver, receives the message on the IP and
> > port, the message which was directed for it. I want to have same
> > behavior. But it seems that it is not possible in MPI. Isn't it?
> >
> > regards,
> > Mudassar
> >
> >------------------------------------------------------------------------> > *From:* Jeff Squyres <jsquy...@cisco.com<mailto:jsquy...@cisco.com> <mailto:jsquy...@cisco.com<mailto:jsquy...@cisco.com>>>> > *To:* Mudassar Majeed <mudassar...@yahoo.com<mailto:mudassar...@yahoo.com>
> <mailto:mudassar...@yahoo.com <mailto:mudassar...@yahoo.com>>>
> > *Cc:* Open MPI Users <us...@open-mpi.org<mailto:us...@open-mpi.org> <mailto:us...@open-mpi.org<mailto:us...@open-mpi.org>>>
> > *Sent:* Friday, July 15, 2011 3:30 AM
> > *Subject:* Re: [OMPI users] Urgent Question regarding,MPI_ANY_SOURCE.
> >
> > Right.  I thought you were asking about receiving *another* message
> > from whomever you just received from via ANY_SOURCE.
> >
> > If you want to receive from a specific sender, you just specify the
> > rank you want to receive from -- not ANY_SOURCE.
> >
> > You will always only receive messages that were sent to *you*.
> > There's no MPI_SEND_TO_ANYONE_WHO_IS_LISTENING functionality, for
> > example.  So your last statement: "But when it captures with ..
> > MPI_ANY_SOURCE and MPI_ANY_TAG, the receiver will capture any message
> > (even not targetted for it)" is incorrect.
> >
> > I guess I still don't understand your question...?
> >
> >
> > On Jul 14, 2011, at 9:17 PM, Mudassar Majeed wrote:
> >
> > >
> > > I know this, but when I compare status.MPI_SOURCE with myid, they
> > are different. I guess you need to reconsider my question. The
> > MPI_Recv function seems to capture message from the queue with some
> > search parameters like source, tag etc. So in case the receiver does
> > not know the sender and wants to receive only that message which was
> > sent for this receiver. But when it captures with source as
> > MPI_ANY_SOURCE and MPI_ANY_TAG, the receiver will capture any message
> > (even not targetted for it).
> > >
> > > regards,
> > > Mudassar
> > >
> > >
> > > From: Jeff Squyres <jsquy...@cisco.com<mailto:jsquy...@cisco.com> <mailto:jsquy...@cisco.com<mailto:jsquy...@cisco.com>>> <mailto:jsquy...@cisco.com <mailto:jsquy...@cisco.com><mailto:jsquy...@cisco.com <mailto:jsquy...@cisco.com>>>>> > > To: Mudassar Majeed <mudassar...@yahoo.com<mailto:mudassar...@yahoo.com>
> <mailto:mudassar...@yahoo.com <mailto:mudassar...@yahoo.com>>
> > <mailto:mudassar...@yahoo.com <mailto:mudassar...@yahoo.com><mailto:mudassar...@yahoo.com <mailto:mudassar...@yahoo.com>>>>; Open> MPI Users <us...@open-mpi.org <mailto:us...@open-mpi.org><mailto:us...@open-mpi.org <mailto:us...@open-mpi.org>>> > <mailto:us...@open-mpi.org <mailto:us...@open-mpi.org><mailto:us...@open-mpi.org <mailto:us...@open-mpi.org>>>>
> > > Sent: Friday, July 15, 2011 1:58 AM
> > > Subject: Re: [OMPI users] Urgent Question regarding,MPI_ANY_SOURCE.
> > >
> > > When you use MPI_ANY_SOURCE in a receive, the rank of the actual
> > sender is passed back to you in the status.MPI_SOURCE.
> > >
> > > On Jul 14, 2011, at 7:55 PM, Mudassar Majeed wrote:
> > >
> > > > Hello people,
> > > >                        I am trapped in the following problem plz
> > help me. Suppose a process A sends a message to process B. Theprocess
> > B will receive the message with MPI_Recv with MPI_ANY_SOURCE in the
> > source argument. Let say process B does not know that A is thesender.
> > But I want B to receive message from process A (the one who actually
> > sends the message to process B). But if I use MPI_ANY_SOURCE,then any
> > message from any source is captured by process B (let say there are
> > other processes sending messages). Instead of MPI_ANY_SOURCE I cannot
> > use A in the source argument as B does not know about the sender.What
> > should I do in this situation ?
> > > >
> > > > regards,
> > > > Mudassar Majeed
--
Oracle
Terry D. Dontje | Principal Software Engineer
Developer Tools Engineering | +1.781.442.2631
Oracle *- Performance Technologies*
95 Network Drive, Burlington, MA 01803
Email terry.don...@oracle.com <mailto:terry.don...@oracle.com>


--
Oracle
Terry D. Dontje | Principal Software Engineer
Developer Tools Engineering | +1.781.442.2631
Oracle *- Performance Technologies*
95 Network Drive, Burlington, MA 01803
Email terry.don...@oracle.com <mailto:terry.don...@oracle.com>

Re: [OMPI users] Urgent Question regarding, MPI_ANY_SOURCE.

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