openmpi loses output across multiple nodes

Axel akoh... at
Tue Jul 22 23:06:59 CEST 2008

On Jul 22, 4:46 pm, Eric Shamay <eric.... at> wrote:
> 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.


how verbose is your output? it may be switched to buffered mode
(4k) for performance reasons. try the -i and -o flags for input
and output.


> 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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