Alex,
just ask MPI_Comm_spawn to start (up to) 5 tasks via the maxprocs
parameter :
int MPI_Comm_spawn(char *command, char *argv[], int maxprocs,
MPI_Info info,
int root, MPI_Comm comm, MPI_Comm *intercomm,
int array_of_errcodes[])
INPUT PARAMETERS
maxprocs
- maximum number of processes to start (integer,
significant only at root)
Cheers,
Gilles
On 2014/12/12 12:23, Alex A. Schmidt wrote:
> Hello Gilles,
>
> Thanks for your reply. The "env -i PATH=..." stuff seems to work!!!
>
> call system("sh -c 'env -i PATH=/usr/lib64/openmpi/bin:/bin mpirun -n 2
> hello_world' ")
>
> did produce the expected result with a simple openmi "hello_world" code I
> wrote.
>
> I might be harder though with the real third party app I have in mind. And
> I realize
> getting passed over a job scheduler with this approach might not work at
> all...
>
> I have looked at the MPI_Comm_spawn call but I failed to understand how it
> could help here. For instance, can I use it to launch an mpi app with the
> option "-n 5" ?
>
> Alex
>
> 2014-12-12 0:36 GMT-02:00 Gilles Gouaillardet <gilles.gouaillar...@iferc.org
>> :
>>
>> Alex,
>>
>> can you try something like
>> call system(sh -c 'env -i /.../mpirun -np 2 /.../app_name')
>>
>> -i start with an empty environment
>> that being said, you might need to set a few environment variables
>> manually :
>> env -i PATH=/bin ...
>>
>> and that being also said, this "trick" could be just a bad idea :
>> you might be using a scheduler, and if you empty the environment, the
>> scheduler
>> will not be aware of the "inside" run.
>>
>> on top of that, invoking system might fail depending on the interconnect
>> you use.
>>
>> Bottom line, i believe Ralph's reply is still valid, even if five years
>> have passed :
>> changing your workflow, or using MPI_Comm_spawn is a much better approach.
>>
>> Cheers,
>>
>> Gilles
>>
>> On 2014/12/12 11:22, Alex A. Schmidt wrote:
>>
>> Dear OpenMPI users,
>>
>> Regarding to this previous
>> post<http://www.open-mpi.org/community/lists/users/2009/06/9560.php>
>> <http://www.open-mpi.org/community/lists/users/2009/06/9560.php> from 2009,
>> I wonder if the reply
>> from Ralph Castain is still valid. My need is similar but quite simpler:
>> to make a system call from an openmpi fortran application to run a
>> third party openmpi application. I don't need to exchange mpi messages
>> with the application. I just need to read the resulting output file
>> generated
>> by it. I have tried to do the following system call from my fortran openmpi
>> code:
>>
>> call system("sh -c 'mpirun -n 2 app_name")
>>
>> but I get
>>
>> **********************************************************
>>
>> Open MPI does not support recursive calls of mpirun
>>
>> **********************************************************
>>
>> Is there a way to make this work?
>>
>> Best regards,
>>
>> Alex
>>
>>
>>
>>
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>>
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>
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