Hi All,
I'm having this weird problem when running a very simple OpenMPI application.
The application sends an integer from the rank 0 process to the rank 1 process.
The sequence of code that I use to accomplish this is the following:
if (rank == 0)
{
printf("Process %d - Sending...\n", rank);
MPI_Send(&sent, 1, MPI_INT, 1, 1, MPI_COMM_WORLD);
printf("Process %d - Sent.\n", rank);
}
if (rank == 1)
{
printf("Process %d - Receiving...\n", rank);
MPI_Recv(&received, 1, MPI_INT, 0, 1, MPI_COMM_WORLD, &stat);
printf("Process %d - Received.\n", rank");
}
printf("Process %d - Barrier reached.\n", rank);
MPI_Barrier(MPI_COMM_WORLD);
printf("Process %d - Barrier passed.\n", rank");
Like I said, a very simple program.
When launching this application with SLURM (using "salloc -N2 mpirun
./<my_app>"), it hangs at the barrier. 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), the operating system on the
cluster on which I tried to run my application is Ubuntu 10.04 LTS Server x64.
If anyone is willing to help me out, I will happily provide any other info
requested (as long as the request comes with instructions on how to get that
info).
Your answers will be of great help! Thanks!
Adrian
