The only example that works is hello_c.c. All others (that use MPI_Send and MPI_Recv)(connectivity_c.c and ring_c.c) block after the first MPI_Send / MPI_Recv (although the first Send/Receive pair works well for all processes, subsequent Send/Receive pairs block). My slurm version is 2.1.0. It is also worth mentioning that all examples work when not using SLURM (launching with "mpirun -np 5 <exaple_app>"). Blocking occurs only when I try to run on multiple hosts with SLURM ("salloc -N5 mpirun <example_app>").


From: Jeff Squyres <jsquyres@cisco.com>
To: adrian sabou <adrian.sabou@yahoo.com>; Open MPI Users <users@open-mpi.org>
Sent: Wednesday, February 1, 2012 10:32 PM
Subject: Re: [OMPI users] OpenMPI / SLURM -> Send/Recv blocking

On Jan 31, 2012, at 11:16 AM, adrian sabou wrote:

> Like I said, a very simple program.
> When launching this application with SLURM (using "salloc -N2 mpirun ./<my_app>"), it hangs at the barrier.

Are you able to run the MPI example programs in examples/ ?

> However, it passes the barrier if I launch it without SLURM (using "mpirun -np 2 ./<my_app>"). I first noticed this problem when my application hanged if I tried to send two successive messages from a process to another. Only the first MPI_Send would work. The second MPI_Send would block indefinitely. I was wondering whether any of you have encountered a similar problem, or may have an ideea as to what is causing the Send/Receive pair to block when using SLURM. The exact output in my console is as follows:

>        salloc: Granted job allocation 1138
>        Process 0 - Sending...
>        Process 1 - Receiving...
>        Process 1 - Received.
>        Process 1 - Barrier reached.
>        Process 0 - Sent.
>        Process 0 - Barrier reached.
>        (it just hangs here)

> I am new to MPI programming and to OpenMPI and would greatly appreciate any help. My OpenMPI version is 1.4.4 (although I have also tried it on 1.5.4), my SLURM version is 0.3.3-1 (slurm-llnl 2.1.0-1),

I'm not sure what SLURM version that is -- my "srun --version" shows 2.2.4.  0.3.3 would be pretty ancient, no?

Jeff Squyres
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