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Subject: [OMPI users] MPI Program hangs when runs on more than one host
From: long thai (thaithanhlong2501_at_[hidden])
Date: 2010-04-20 02:39:42


Hi all.

I'm just using OpenMPI for few days. I'll try to run a simple MPI program,
the program is ProcessColors which I get from
CI-Tutor<http://ci-tutor.ncsa.illinois.edu/content.php?cid=1091>.
I have 2 hosts, if I run the program separately on each one, it runs well.
However, if I run it on two hosts using following command: *mpirun --host
host1,host2 --preload-binary -np 8 ProcessColors*. The program hangs.

When I use command *ps -A* to check running process, I find out that there
is 4 processes running on each host. So, I think that there is a deadlock on
my program, but why it runs well with single host?

All those following commands run without any problem on both machine:

   - mpirun -np 8 ProcessColors
   - mpirun --host host1 -np 8 ProcessColors
   - mpirun --host host2 -np 8 ProcessColors

Later, I found out that the problem comes when the remote host try to send
message to the host which root process (process 0) is running, which is the
host that I run the command. I don't know why the process is blocked at
sending task.

Any help from you is precious to me.

Regards.

Long Thai.