[mpich-discuss] Processor hangs on MPI_Comm_accept

[Alberto Giannetti]

On May 7, 2008, at 3:26 PM, Rajeev Thakur wrote:

> If you use MPI_COMM_SELF on the server side and MPI_COMM_WORLD on  
> the client
> side, it won't work. Using MPI_COMM_WORLD in MPI_Comm_connect makes  
> it one
> collective connect. The port name passed on the non-root rank is  
> ignored.

The MPI_Comm_connect succeeds for both processors.
Why a client collective connect would not work?

> If
> you use MPI_COMM_SELF on both sides, it becomes two separate  
> connects that
> match the two separate accepts.
>
> Rajeev
>
>
>> -----Original Message-----
>> From: owner-mpich-discuss at mcs.anl.gov
>> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Alberto
>> Giannetti
>> Sent: Wednesday, May 07, 2008 1:41 PM
>> To: mpich-discuss at mcs.anl.gov
>> Subject: [mpich-discuss] Processor hangs on MPI_Comm_accept
>>
>> Resending with regular file attachments.
>>
>> I have two simple programs that connect through a MPI_Connect/
>> MPI_Accept scheme.
>> client.c look for a service published by server.c, connects and
>> create an intercomm to send a message, then waits for a message from
>> the server and finally disconnects from the intercomm. I run both
>> client and server with 2 processors:
>>
>> mpiexec -n 2 server
>> mpiexec -n 2 client myfriend
>>
>> Everything works if I call both MPI_Comm_connect and MPI_Comm_accept
>> using the MPI_COMM_SELF group. However, if I use MPI_COMM_WORLD on
>> the MPI_Connect() client call, one of the two server processors
>> hangs. My trace shows that the client connects to the server,
>> but the
>> server never leaves MPI_Comm_accept():
>>
>> Client trace:
>> Processor 0 (1463, Sender) initialized
>> Processor 0 looking for service myfriend-0
>> Processor 1 (1462, Sender) initialized
>> Processor 1 looking for service myfriend-1
>> Processor 0 found port tag#0$port#53996$description#192.168.0.10
>> $ifname#192.168.0.10$ looking for service myfriend-0
>> Processor 0 connecting to 'tag#0$port#53996$description#192.168.0.10
>> $ifname#192.168.0.10$'
>> Processor 1 found port tag#0$port#53995$description#192.168.0.10
>> $ifname#192.168.0.10$ looking for service myfriend-1
>> Processor 1 connecting to 'tag#0$port#53995$description#192.168.0.10
>> $ifname#192.168.0.10$'
>> Processor 1 connected
>> Processor 1 remote comm size is 1
>> Processor 1 sending data through intercomm to rank 0...
>> Processor 0 connected
>> Processor 0 remote comm size is 1
>> Processor 0 sending data through intercomm to rank 0...
>> Processor 1 data sent!
>> Processor 0 data sent!
>> Processor 0 received string data 'ciao client' from rank 0, tag 0
>> Processor 0 disconnecting communicator
>> Processor 0 finalizing
>>
>> Server trace:
>> Processor 0 (1456, Receiver) initialized
>> Processor 0 opened port tag#0$port#53996$description#192.168.0.10
>> $ifname#192.168.0.10$
>> Publishing port tag#0$port#53996$description#192.168.0.10
>> $ifname#192.168.0.10$ as service myfriend-0
>> Processor 1 (1455, Receiver) initialized
>> Processor 1 opened port tag#0$port#53995$description#192.168.0.10
>> $ifname#192.168.0.10$
>> Publishing port tag#0$port#53995$description#192.168.0.10
>> $ifname#192.168.0.10$ as service myfriend-1
>> Processor 1 waiting for connections on tag#0$port#53995
>> $description#192.168.0.10$ifname#192.168.0.10$, service myfriend-1...
>> Processor 0 waiting for connections on tag#0$port#53996
>> $description#192.168.0.10$ifname#192.168.0.10$, service myfriend-0...
>> Processor 0 new connection on port tag#0$port#53996
>> $description#192.168.0.10$ifname#192.168.0.10$
>> Processor 0 closing port tag#0$port#53996$description#192.168.0.10
>> $ifname#192.168.0.10$
>> Processor 0 unpublishing service myfriend-0
>> Processor 0 remote comm size is 2
>> Processor 0 waiting for data from new intercomm...
>> Processor 0 got 100 elements from rank 1, tag 1: 0.000000, 1.000000,
>> 2.000000...
>> Processor 0 sending string back...
>> Processor 0 data sent
>> Processor 0 disconnecting communicator
>>
>>
>>
>