openmpi loses output across multiple nodes

Eric Shamay eric.... at gmail.com
Tue Jul 22 22:46:09 CEST 2008


Hello all,

I've succeeded in compiling the parallel cp2k, and have run the
benchmarks included (as well as my own simulations) to satisfy myself
that indeed all is as it seems. Everything works fine when running on
a single node.

When running on 2 processors on a single node I issue:

mpirun -np 2 cp2k.popt <input file>

all is well. Output looks fine and the cpus are both running at 100%.

When trying to run the program on 2 nodes (identical hardware and
software setup) I run into a problem. I have a host file for openmpi
that lists the processors, 2 cpus per node, and the networking seems
to be fine. I issue the command:

mpirun -np 4 -machinefile ~/hostfile cp2k.popt <input file>

and the 4 processes seem to fire up just fine: 2 processes per node
are running and all 4 processes use 100% of each cpu. However, I don't
have any output from cp2k. It seems as though the head node that runs
the mpirun command just gets all the processors running but can no
longer speak to stdout or do any type of I/O.

I'm not sure if this is a common problem but I'm at a loss as to
searches in the man pages, documentation, and on the forum and on
google, etc. Does anyone know what might be happening?

Thanks,
~Eric


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