[Beowulf] Clos networking and myrinet

[Greg Lindahl]

> >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 ?

For only a pair of nodes, a switch is always nonblocking. Do you build
a lot of 2 node clusters? ;-) You could save some money by getting rid
of the switch...

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.

> It looks for me that both Myrinet and Infiniband topologies
> specially support "Clos-network configurations" ...

Yes. The InfiniBand people use different jargon (CBB: constant
bisection bandwidth) but it boils down to the same thing.

-- greg