[Beowulf] Shared memory

John Hearns john.hearns at streamline-computing.com
Thu Jun 23 00:44:32 PDT 2005

On Wed, 2005-06-22 at 08:46 +0100, Mark Westwood wrote:

> My thinking is that mixed-mode programming, in which a code uses MPI for 
> inter-node communication and shared-memory programming (eg OpenMP) for 
> intra-node communication, is not worth the effort when you only have 2 
> CPUs in each node.  In fact, my thinking is that it's not even worth the 
> time experimenting to gather evidence.  I guess that makes me prejudiced 
> against mixed-mode programming on a typical COTS cluster.  Now, if you 
> were to offer me, say, 8 or 16 CPUs per node, I might think again.  Or 
> indeed if I am shot down in flames by contributors to this list who have 
> done the experiments ...
Mark, that is very well put.

May I add that 8 or 16 CPUs per node has become a realistic possibility?
Four and eight way(*) Opteron machines are available, up to 128Gbytes
Expect to see more of these machines out there as engineering
workstations or for visualisation and animation/rendering.

Add dual-core CPUs to the mix and you get a very attractive platform.

(*) two quad motherboards, so I guess realistically and 8-way OpenMP is
the limit

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