[mpich-discuss] How to terminate MPI_Comm_accept

[Roy, Hirak]

Hi Pavan,

Here is my code for thread2 :

do {
    MPI_Comm newComm ;
    MPI_Comm_accept (m_serverPort.c_str(), MPI_INFO_NULL, 0, MPI_COMM_SELF, &newComm);
    Log ("Accepted a connection");
    int buf = 0 ;
    MPI_Status status ;
    MPI_Recv(&buf, 1, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, newComm, &status);

    if (status.MPI_TAG == MPI_MSG_TAG_NEW_CONN) {
      m_clientComs[m_clientCount] = newComm ;
      m_clientCount++;
    } else if (status.MPI_TAG == MPI_MSG_TAG_SHUTDOWN) {
      Log ("Shutdown");
      //MPI_Comm_disconnect (&newComm);
     Log ("Disconnect");
      break;
    } else {
      Log ("Unmatched Receive");
    }
  } while(1) ;


Here is my code for thread1 to terminate thread2 :

  MPI_Comm newComm ;
  MPI_Comm_connect (m_serverPort.c_str(), MPI_INFO_NULL, 0, MPI_COMM_SELF, &newComm);
  Log ("Connect to Self");
  int val = 0 ;
  MPI_Request req ;
  MPI_Send(&val, 1, MPI_INT, 0, MPI_MSG_TAG_SHUTDOWN, newComm);
  Log ("Successful");
  //MPI_Status stat ;
  //MPI_Wait(&req, &stat);
  Log ("Complete");

  //MPI_Comm_disconnect(&newComm);




The MPI_Send/Recv waits.
I am using sock channel.
For nemesis, I get the following crash :
Assertion failed in file ./src/mpid/ch3/channels/nemesis/include/mpid_nem_inline.h at line 58: vc_ch->is_local
internal ABORT - process 0

I tried non-blocking send and receive followed by wait. However, that also does not solve the problem.

Thanks,
Hirak



-----

Hirak,

Your approach should work fine.  I'm not sure what issue you are facing.  I assume thread 1 is doing this:

while (1) {
        MPI_Comm_accept(..);
        MPI_Recv(.., tag, ..);
        if (tag == REGULAR_CONNECTION)
               continue;
        else if (tag == TERMINATION) {
               MPI_Send(..);
               break;
        }
}

In this case, all clients do an MPI_Comm_connect and then send a message with tag = REGULAR_CONNECTION.  When thread 2 is done with its work, it'll do an MPI_Comm_connect and then send a message with tag = TERMINATION, wait for a response from thread 1, and call finalize.

  - Pavan

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