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Subject: Re: [OMPI users] MPI Program hangs when runs on more than one host
From: Changsheng Jiang (jiangzuoyan_at_[hidden])
Date: 2010-04-20 04:54:45

I have encountered the same problem too.

By gdb attached, it's show that the processes are in a loop of (e)poll.
After configuring the network interface in ~/.openmpi/mca-params.conf using
btl_tcp_if_include, all hosts work fine.

just fyi.
                                                     Changsheng Jiang

On Tue, Apr 20, 2010 at 14:39, long thai <thaithanhlong2501_at_[hidden]>wrote:

> 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<>.
> 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.
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