Feel free to correct me if im wrong.
OMPI assumes you have a fast network and checks for them. If they
are not found it falls back to tcp.
So if you leave out the --mca etc etc.... It should use the mx if
its available. Im not sure how MX responds if one of the hosts does
not have a working card (not activated) because the mpi job will
still run. Just not using MX to that host. All other hosts will us MX.
If openmpi sees that a node has more than one cpu (SMP) It will use
the sm (shared mem) method to communicate over the mx. and if a
proc sends to its self, the self method is used. So its like a
priority order.
I know there is a way (its in the archives) to see the priority on
how OMPI choses what method to use. and uses the highest priority
that will allow the communication to complete.
I know there is also some magic being working on/implemented. That
will stripe over multiple networks for large messages when more
bandwidth is needed. I dont know if OMPI will have this ability or
not. Someone else can chime in on that.
Brock Palen
Center for Advanced Computing
bro...@umich.edu
(734)936-1985
On Nov 21, 2006, at 11:28 PM, Iannetti, Anthony C. ((GRC-RTB0)) wrote:
Dear OpenMPI List:
From looking at a recent thread, I see an mpirun command with
shared memory and mx:
mpirun –mca btl mx,sm,self –np 2 pi3f90.x
This works. I may have forgot to mention it, but I am using
1.1.2. I see there is an –mca mtl in version 1.2b1 . I do not
think this exists in 1.1.2.
Still, I would like to know what –mca is given automatically.
Thanks,
Tony
Anthony C. Iannetti, P.E.
NASA Glenn Research Center
Propulsion Systems Division, Combustion Branch
21000 Brookpark Road, MS 5-10
Cleveland, OH 44135
phone: (216)433-5586
email: anthony.c.ianne...@nasa.gov
Please note: All opinions expressed in this message are my own and
NOT of NASA. Only the NASA Administrator can speak on behalf of NASA.
From: Iannetti, Anthony C. (GRC-RTB0)
Sent: Tuesday, November 21, 2006 8:39 PM
To: 'us...@open-mpi.org'
Subject: MX performance problem on two processor nodes
Dear OpenMPI List:
I am running the Myrinet MX btl with OpenMPI on MacOSX
10.4. I am running into a problem. When I run on one processor
per node, OpenMPI runs just fine. When I run on two processors
per node (slots=2), it seems to take forever (something is hanging).
Here is the command:
mpirun –mca btl mx,self –np 2 pi3f90.x
However, if I give the command:
mpirun –np 2 pi3f90.x
The process runs normally. But, I do not know if it is using the
Myrinet network. Is there a way to diagnose this problem. mpirun –
v and –d do not seem to indicate which mca is actually being used.
Thanks,
Tony
Anthony C. Iannetti, P.E.
NASA Glenn Research Center
Propulsion Systems Division, Combustion Branch
21000 Brookpark Road, MS 5-10
Cleveland, OH 44135
phone: (216)433-5586
email: anthony.c.ianne...@nasa.gov
Please note: All opinions expressed in this message are my own and
NOT of NASA. Only the NASA Administrator can speak on behalf of NASA.
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