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Subject: Re: [OMPI users] MPI over tcp
From: Rolf vandeVaart (rvandevaart_at_[hidden])
Date: 2012-05-03 17:16:58

I tried your program on a single node and it worked fine. Yes, TCP message passing in Open MPI has been working well for some time.
I have a few suggestions.
1. Can you run something like hostname successfully (mpirun -np 10 -hostfile yourhostfile hostname)
2. If that works, then you can also run with a debug switch to see what connections are being made by MPI.

I would suggest reading through here for some ideas and for the debug switch.


>-----Original Message-----
>From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]]
>On Behalf Of Don Armstrong
>Sent: Thursday, May 03, 2012 2:51 PM
>To: users_at_[hidden]
>Subject: [OMPI users] MPI over tcp
>I'm attempting to use MPI over tcp; the attached (rather trivial) code gets
>stuck in MPI_Send. Looking at TCP dumps indicates that the TCP connection is
>made successfully to the right port, but the actual data doesn't appear to be
>I'm beginning to suspect that there's some basic problem with my
>configuration, or an underlying bug in TCP message passing in MPI. Any
>suggestions to try (or a response indicating that MPI over TCP actually works,
>and that it's some problem with my setup) appreciated.
>The relevant portion of the hostfile looks like this:
> slots=2
> slots=8
>and the output of the run and tcpdump is attached.
>Thanks in advance.
>Don Armstrong
>[T]he question of whether Machines Can Think, [...] is about as relevant as the
>question of whether Submarines Can Swim.
> -- Edsger W. Dijkstra "The threats to computing science"

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