[Beowulf] mpirun and line buffering

Larry Stewart stewart at serissa.com
Tue Oct 27 06:33:07 PDT 2009

On Mon, Oct 26, 2009 at 11:35 AM, Daniel Kidger <daniel.kidger at bull.co.uk>wrote:

> Folks,
> I have an benchmark code that uses printf  on each MPI process to print
> performance figures.
> On the system that the original author's developed on, the output from each
> process must have been line buffereed.
As Ashley says, the job control system deals with this.  I'm familiar with
slurm, for example, which
line-buffers output from each rank and can prepend output with the rank ID.
 Slurm can also direct
output from each rank to an individual file.  What job control system are
you using?  Check the
man page for the job launch command to see if there are switches to control

Other ideas - there are probably environment variables to tell the rank
which rank it is, to find
out see the documentation or run a  two-rank "printenv".  Then you could
redirect each rank's
output separately as   program >output-from-rank-$RANK  or whatever.

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