PetscCommDuplicate#

Duplicates the communicator only if it is not already a PETSc communicator.

Synopsis#

#include "petscsys.h"   
PetscErrorCode PetscCommDuplicate(MPI_Comm comm_in, MPI_Comm *comm_out, PetscMPIInt *first_tag)

Collective

Input Parameter#

  • comm_in - Input communicator

Output Parameters#

  • comm_out - Output communicator. May be comm_in.

  • first_tag - Tag available that has not already been used with this communicator (you may pass in NULL if you do not need a tag)

Note#

PETSc communicators are just regular MPI communicators that keep track of which tags have been used to prevent tag conflict. If you pass a non-PETSc communicator into a PETSc creation routine it will attach a private communicator for use in the objects communications. The internal MPI_Comm is used to perform all the MPI calls for PETSc, the outer MPI_Comm is a user level MPI_Comm that may be performing communication for the user or other library and so IS NOT used by PETSc.

See Also#

PetscObjectGetNewTag(), PetscCommGetNewTag(), PetscCommDestroy()

Level#

developer

Location#

src/sys/objects/tagm.c

Examples#

src/ksp/ksp/tutorials/ex73.c

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