Hi Gilbert,
Checksums are turned off by default. If you need checksums to be activated add "-mca pml csum" to the mpirun command line.
Checksums are enabled only for inter-node communication. Intra-node communication is typically over shared memory and hence checksum is disabled for this case.
If you have built a debug version of Open MPI (--enable-debug), you can see the checksum output by appending "-mca pml_base_verbose 5" to your command line.
If you are interested in the relevant code it is located here - ompi/mca/pml/csum

--Nysal

On Tue, Aug 31, 2010 at 1:22 PM, Gilbert Grosdidier <grodid@mail.cern.ch> wrote:
Bonjour,

I'm not sure I understand how to trigger CHECKSUM use
inside of OpenMPI 1.4.1 (after digging in the FAQs, I got not explanations, sorry):

- Is checksuming activated by default and embedded automatically
within the Send/Recv pair mechanism, please ?
- If not, which MCA param(S) should I set to activate it ?
- Is there a time penalty for using it, please ?

Thanks in advance for any help.

--
Regards, Gilbert.



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