Topology
C | Fortran-2008 | Fortran-90
MPI_Comm_get_parent allows to obtain a handle on the parent communicator, if any. In case the calling MPI process was not spawned by another MPI process, hence having no parent communicator, MPI_Comm_get_parent will set the communicator handle passed to MPI_COMM_NULL instead. By default, the name of the parent communicator will be MPI_COMM_PARENT.
int MPI_Comm_get_parent(MPI_Comm* parent);A pointer to the MPI communicator in which store the handle on the parent communicator if any or MPI_COMM_NULL where appropriate.
The error code returned from the parent communicator retrieval:
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
/**
* @brief Illustrates how to find the parent communicator of an MPI process.
**/
int main(int argc, char* argv[])
{
MPI_Init(&argc, &argv);
MPI_Comm parent;
MPI_Comm_get_parent(&parent);
if(parent == MPI_COMM_NULL)
{
// We have no parent communicator so we have been spawned directly by the user
MPI_Comm child;
int spawn_error;
printf("We are processes spawned directly by you, we now spawn a new instance of an MPI application.\n");
MPI_Comm_spawn(argv[0], MPI_ARGV_NULL, 1, MPI_INFO_NULL, 0, MPI_COMM_WORLD, &child, &spawn_error);
}
else
{
// We have been spawned by another MPI process
printf("I have been spawned by MPI processes.\n");
}
MPI_Finalize();
return EXIT_SUCCESS;
}