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Name
MPI_Comm_create - Creates a new communicator.
Syntax
C Syntax
#include <mpi.h>
int MPI_Comm_create(MPI_Comm comm, MPI_Group group, MPI_Comm *newcomm)
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_CREATE(COMM, GROUP, NEWCOMM, IERROR)
INTEGER COMM, GROUP, NEWCOMM, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Comm_create(comm, group, newcomm, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm
TYPE(MPI_Group), INTENT(IN) :: group
TYPE(MPI_Comm), INTENT(OUT) :: newcomm
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Input Parameter
comm: Communicator (handle).group: Group, which is a subset of the group of comm (handle).
Output Parameters
newcomm: New communicator (handle).IERROR: Fortran only: Error status (integer).
Description
This function creates a new communicator newcomm with communication
group defined by group and a new context. The function sets newcomm to
a new communicator that spans all the processes that are in the group.
It sets newcomm to MPI_COMM_NULL for processes that are not in the
group.
Each process must call with a group argument that is a subgroup of the
group associated with comm; this could be MPI_GROUP_EMPTY. The
processes may specify different values for the group argument. If a
process calls with a non-empty group, then all processes in that group
must call the function with the same group as argument, that is: the
same processes in the same order. Otherwise the call is erroneous.
Notes
MPI_Comm_create provides a means of making a subset of processes for the
purpose of separate MIMD computation, with separate communication space.
newcomm, which is created by MPI_Comm_create, can be used in
subsequent calls to MPI_Comm_create (or other communicator constructors)
to further subdivide a computation into parallel sub-computations. A
more general service is provided by MPI_Comm_split.
Errors
Almost all MPI routines return an error value; C routines as the value
of the function and Fortran routines in the last argument.
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
may be used to cause error values to be returned. Note that MPI does not
guarantee that an MPI program can continue past an error.
See Also
MPI_Comm_split(3)
MPI_Intercomm_create(3)
MPI_Comm_create_group(3)