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¶
INCLUDE 'mpif.h'
MPI_COMM_CREATE( COMM, GROUP, NEWCOMM, IERROR)
INTEGER COMM, GROUP, NEW, IERROR
C++ Syntax¶
#include <mpi.h>
MPI::Intercomm MPI::Intercomm::Create(const Group& group) const
MPI::Intracomm MPI::Intracomm::Create(const Group& group) const
- 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. C++ functions 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