[Beowulf] myrinet (scali) or ethernet

Håvard Wall haavardw at ifi.uio.no
Wed Oct 6 02:52:53 EDT 2004

Joachim Worringen wrote:
> Patricia wrote:
> With Scali ("MPI Connect"), it's more complicated as it can fallback to 
> Ethernet if the other interconnect (SCI?) does not work. Just run a 
> ping-pong benchmark to measure latency (there's one included with Scali 
> MPI), and if you get < 10us latency, you are not using Ethernet. Next to 
> this, there should also be diagnostic tools included.

With Scampi MPI Connect, you can check which interconnects are in use by 
setting the environment variable SCAMPI_NETWORKS_VERBOSE=2.

It is true that scampi will try to fallback to another interconnect if 
the primary fails. The interconnects used is listed in 
/opt/scali/etc/ScaMPI.conf. You may override this by setting the 
environment variable SCAMPI_NETWORKS (or use the -net switch with 
mpimon). For example SCAMPI_NETWORKS="smp,sci,tcp" will first try 
communication through shared memory, then SCI, and at last (tcp) if this 

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