On Feb 13, 2011, at 4:07 AM, Brice Goglin wrote:
>> $ mpirun -np 4 hwloc-bind socket:0.core:0-3 ./test
>>
>> 1. Does hwloc-bind map the processes *sequentially* on *successive* cores of
>> the socket?
>
> No. Each hwloc-bind command in the mpirun above doesn't know that there are
> other hwloc-bind instances on the same machine. All of them bind their
> process to all cores in the first socket.
To further underscore this point, mpirun launched 4 copies of:
hwloc-bind socket:0.core:0-3 ./test
Which means that all 4 processes bound to exactly the same thing.
If you want each process to bind to a *different* set of PU's, then you have
two choices:
1. See Open MPI 1.5.1's mpirun(1) man page. There's new affinity options in
the OMPI 1.5 series, such as --bind-to-core and --bind-to-socket. We wrote
them up in the FAQ, too.
2. Write a wrapper script that looks at the Open MPI environment variables
OMPI_COMM_WORLD_RANK, or OMPI_COMM_WORLD_LOCAL_RANK, or
OMPI_COMM_WORLD_NODE_RANK and decides how to invoke hwloc-bind. For example,
something like this:
mpirun -np 4 my_wrapper.sh ./test
where my_wrapper.sh is:
-----
#!/bin/sh
if test "$OMPI_COMM_WORLD_RANK" = "0"; then
bind_string=...whatever...
else
bind_string=...whatever...
fi
hwloc-bind $bind_string $*
-----
Something like that.
--
Jeff Squyres
jsquy...@cisco.com
For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/
