[Beowulf] mpirun and line buffering

Håkon Bugge h-bugge at online.no
Tue Oct 27 00:17:31 PDT 2009

Use an MPI where you can control the buffering. Line of character  
buffering would suffice in your case. Setting the line buffering in  
the MPI process itself might not be sufficient, depending on how the  
stdout/err is transported back to your (assumed) terminal.


On Oct 26, 2009, at 16:35 , Daniel Kidger 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.
> On the QDR IB system I have testing on, the printf from each process  
> is not line buffered and so the output is largely unreadable as all  
> the lines have been jumbled together.
> Is this a known issue with a workaround? or does everyone else only  
> print from just one MPI process?
> Daniel
> -- 
> Bull, Architect of an Open World TM
> Dr. Daniel Kidger, HPC Technical Consultant
> daniel.kidger at bull.co.uk
> +44 (0) 7966822177
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Håkon Bugge
h-bugge at online.no
+47 924 84 514

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