[MPICH] Binding and instance of the MPI program to a particular processor

[Darius Buntinas]

In linux there's a command called numactl which can be used to execute a 
process and bind it to a physical processor.  Unfortunately, it looks 
like pbind can only bind a process once it has already been started.  If 
you can find a command on sun similar to numactl on linux you can do 
something like what I do with numactl.

With numactl one can do something like this to bind each process to a 
different processor:

mpiexec -n 1 numactl --physcpubind=0 -- myapp myapparg : -n 1 numactl 
--physcpubind=1 -- myapp myapparg : -n 1 numactl --physcpubind=2 -- 
myapp myapparg

etc.

Of course that's messy, so a more general solution would be to write a 
script called, e.g. execbind, to do that:

numactl --physcpubind=`expr $PMI_RANK % $PROCS_PER_NODE` -- $@

Where $PROCS_PER_NODE is the number of processors on each node of your 
cluster, and $PMI_RANK is set by mpiexec.

Then, if you wanted to start 16 processes on a cluster of machines with 
4 cores each, you could simply do:

mpiexec -n 16 -env PROCS_PER_NODE 4 execbind myapp myapparg

Darius

Christina Patrick wrote:
> Is it possible for me to modify the Python script (mpiexec) in such a 
> way that I use the pbind command to bind each instance of the executing 
> program to a different processor? I would like to give that a shot.
>  
> Warm Regards,
> Christina.
> 
>  
> On 6/20/07, *Rajeev Thakur* <thakur at mcs.anl.gov 
> <mailto:thakur at mcs.anl.gov>> wrote:
> 
>     MPICH2 leaves the scheduling of processes to the OS. If the OS has
>     some way
>     to bind processes to processors, you could try using it.
> 
>     Rajeev
> 
>      > -----Original Message-----
>      > From: owner-mpich-discuss at mcs.anl.gov
>     <mailto:owner-mpich-discuss at mcs.anl.gov>
>      > [mailto:owner-mpich-discuss at mcs.anl.gov
>     <mailto:owner-mpich-discuss at mcs.anl.gov>] On Behalf Of
>      > Christina Patrick
>      > Sent: Wednesday, June 20, 2007 4:12 PM
>      > To: mpich-discuss-digest at mcs.anl.gov
>     <mailto:mpich-discuss-digest at mcs.anl.gov>
>      > Subject: [MPICH] Binding and instance of the MPI program to a
>      > particular processor
>      >
>      > Hi everybody,
>      >
>      > I am having a 8 processor Solaris 9 machine and I want to
>      > execute an MPI program on it. The problem is that the tasks
>      > created by mpiexec keep migrating on the different
>      > processors. Since it is only one machine, there is only one
>      > instance of the mpdboot daemon running on the machine. Hence
>      > when I execute the below command on the machine with 8
>      > processors, I get an output that says:
>      >
>      > (For example, if the MPI program name is "finalized")
>      > # mpiexec -n 8 ./finalized
>      > 0:  No Errors
>      >
>      > When I examined the system using the "prstat" command, I
>      > observed that the tasks are migrating between the different
>      > processors.
>      >
>      > Is there any why in which I could bind each instance of the
>      > MPI program to a different processor.
>      >
>      > Your suggesstions and help is appreciated,
>      >
>      > Thanks,
>      > Christina.
>      >
> 
>