should work!

On Jun 6, 2013, at 8:24 AM, José Luis García Pallero <jgpallero@gmail.com> wrote:

2013/6/6 Ralph Castain <rhc@open-mpi.org>
Afraid not. You could start a single process, and then have that process call MPI_Comm_spawn to launch the rest of them

Mmmm... sounds good

I'm writing an example program using ScaLAPACK. I have written the ScaLAPACK code in an independent function that must be called after some work in an individual node (the root one). So I need the first part of the program be executed by one process. My example looks like:

int main()
{
    //some work that must be done by only one node
    .....
    //function that runs internally some scalapack computations
    funcCompScalapack();
    //other work must be done by the original node
    ....
    return 0;
}

void funcCompScalapack()
{
    //Initialize MPI
    MPI_Init(NULL,NULL);
    //here I think I should write some code in order to inform that the work must be done by a number X or processors
    //maybe using MPI_Comm_spawn?
    ....
    //some BLACS and ScaLAPACK computations
    ....
    //finalize MPI
    MPI_Finalize();
    return;
}

When I execute this program as mpirun -np X myprogram, the pieces of code before and after the call to function funcCompScalapack() are executed by X nodes, but these orders must be executed only by one. So my idea is to execute the binary as ./myprogram (the same I think as mpirun -np 1 myprogram) and internally set the number of processes in funcCompScalapack() after the MPI_Init() call.

Is my idea possible?

Thanks
 

On Jun 6, 2013, at 7:54 AM, José Luis García Pallero <jgpallero@gmail.com> wrote:

Hello:

I'm newbie in the use of MPI, so probably I ask some stupid question (or previously asked, but in this case I have searched in the archive and I haven't found anything):

Exists any other way than -np X in order to pass the number of processes to start for an MPI program? I mean a function of the style MPI_Set_Number_Processes() or similar

Thanks

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--
*****************************************
José Luis García Pallero
jgpallero@gmail.com
(o<
/ / \
V_/_
Use Debian GNU/Linux and enjoy!
*****************************************
_______________________________________________
users mailing list
users@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/users