Re: Shared Memory usage in -machinefile

Hi Reuti,

Reuti wrote:
> Question is: how is Myrinet behaving in this case? Different from the default 
> MPICH, or could the above statement give under some circumstances a less 
> optimal result?

node1:2

will be expanded in

node1
node1

The shared memory support in MPICH-GM is very different from the 
-comm=shared of MPICH-P4. When shared memory is enabled (the default) 
all processes from the same MPI job running on the same host (hostname 
is the same) will use shared memory. We don't use IPC for allocated 
shared memory segments (IPC is a mess), so shared memory is either used 
or not used, there is no other variation.

So, you can use ":n" or list the same node n times, there would be no 
difference regarding shared memory.

Patrick
--

Patrick Geoffray
Myricom, Inc.
http://www.myri.com