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Subject: [OMPI users] ompi-restart fails with "found pid in use"
From: ananda.mudar_at_[hidden]
Date: 2010-05-14 11:34:11



I am using open mpi v1.3.4 with BLCR 0.8.2. I have been testing my
openmpi based program on a 3-node cluster (each node is a Intel Nehalem
based dual quad core) and I have been successful in checkpointing and
restarting the program successfully multiple times.


Recently I moved to a 15 node cluster with the same configuration and I
started seeing the problem with ompi-restart.


Ompi-checkpoint gets completed successfully and I terminate the program
after that. I have ensured that there are no MPI processes before I
restarted. When I restart using ompi-restart, I get the error in
restarting few of the MPI processes and the error message is "found pid
4185 in use; Restart failed: Device or Resource busy" (of course with
different pid numbers). What I found was that when the MPI process was
restarted, it got restarted on a different node than what it was running
before termination and found that it cannot reuse the pid.


Unlike cr_restart (BLCR), ompi-restart doesn't have an option to say not
to use the same pid with option such as "--no-restore-pid". Since
ompi-restart in turn calls cr_restart, I tried to alias cr_restart to
"cr_restart --no-restore-pid". This actually made the problem "pid in
use" go away and the process completes successfully. However if I call
ompi-checkpoint on the restarted open MPI job, both the openMPI job (all
MPI processes) and the checkpoint command hang forever. I guess this is
because of the fact that ompi-restart has different set of pids compared
to the actual pids that are running.


Long story short, I am stuck with this problem as I cannot get the
original pids during restart.


I really appreciate if you have any other options to share with me which
I can use to overcome this problem.




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