[Beowulf] Clos networking and myrinet

Patrick Geoffray patrick at myri.com
Wed Jun 8 12:57:21 PDT 2005

Hi Greg,

Greg Lindahl wrote:
>>>In a Linux cluster, each node talks to multiple other nodes. So they
>>>always interfere with each other.
>>Sorry, why is it right ?
>>- for typical example, if I have a pair of nodes w/MPI_Send one 1st
>>and MPI_Recv on second ?

> Seriously, as I said, if you only have each node talking to one other
> node, then the statement about Clos networks being non-blocking is
> true.  But this is not typical for Linux clusters.

I think it's typical to have several nodes talking to several *other* 
nodes, and that's fine with route dispersion. However, it's not typical 
to have several nodes talking to the *same node at the same time*. If it 
happens, the application may not have the choice and it's doomed, or 
it's poorly written and it will always suck.


Patrick Geoffray
Myricom, Inc.

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