[Carpet] component geometry for multi-core processor chips

[Erik Schnetter]

On Aug 28, 2006, at 01:52:15, Steve White wrote:

> Erik,
>
> Further thoughts on this.
>
> First, I think the
> 	ppn=n
> syntax requests a certain number of processes on each node.
>
> Second, it would be better not to ask the specific batch system  
> (PBS) about
> which processes are running on which nodes.  I would prefer a means  
> that
> is independent of batch system.
>
> How about:
>
> 	if this is not the MPI root process
> 		* send to MPI root process the result of
> 			system( "uname -n" )

You mean Util_GetHostName.

> 	otherwise
> 		* make a hash of
> 			node_name, mpi_rank
> 		* wait for message from each other process
> 		* for each message,
> 			add to the hash the the message body with mpi_rank
> 		* add to the hash the present node name with mpi_rank = 0
>
> Now you have an easy association of nodes to MPI rank numbers.

Clever.  I didn't think of that.  I was thinking along the lines of  
running a short benchmark, determining latencies and bandwidths  
between the individual processors.  That would unfortunately be quite  
expensive, since you would need to test each processor pair, and the  
individual communications would influence each other.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>

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