MPI_Comm_create(3) Open MPI MPI_Comm_create(3)
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
C++ Syntax
#include <mpi.h>
MPI::Intercomm MPI::Intercomm::Create(const Group& group) const
MPI::Intracomm MPI::Intracomm::Create(const Group& group) const
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 pro-
cesses 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 construc-
tors) to further subdivide a computation into parallel sub-computa-
tions. 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. C++ func-
tions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
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
MPI_Intercomm_create MPI_Comm_create_group
4.1.2 Nov 24, 2021 MPI_Comm_create(3)
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