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MPI_Comm_create_group - Creates a new communicator.
#include <mpi.h>
int MPI_Comm_create_group(MPI_Comm comm, MPI_Group group, int tag, MPI_Comm
*newcomm)
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_COMM_CREATE_GROUP(COMM, GROUP, TAG, NEWCOMM, IERROR)
INTEGER COMM, GROUP, TAG, NEWCOMM, IERROR
USE mpi_f08
MPI_Comm_create_group(comm, group, tag, newcomm, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm
TYPE(MPI_Group), INTENT(IN) :: group
INTEGER, INTENT(IN) :: tag
TYPE(MPI_Comm), INTENT(OUT) :: newcomm
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- comm
- Communicator (handle).
- group
- Group, which is a subset
of the group of comm (handle).
- tag
- Tag (integer).
- newcomm
- New communicator (handle).
- IERROR
- Fortran only: Error status (integer).
MPI_Comm_create_group is similar to MPI_Comm_create; however,
MPI_Comm_create must be called by all processes in the group of comm, whereas
MPI_Comm_create_group must be called by all processes in group, which is
a subgroup of the group of comm. In addition, MPI_Comm_create_group requires
that comm is an intracommunicator. MPI_Comm_create_group returns a new intracommunicator,
newcomm, for which the group argument defines the communication group. No
cached information propagates from comm to newcomm.
Each process must provide
a group argument that is a subgroup of the group associated with comm;
this could be MPI_GROUP_EMPTY. If a non-empty group is specified, then all
processes in that group must call the function, and each of these processes
must provide the same arguments, including a group that contains the same
members with the same ordering. Otherwise the call is erroneous. If the calling
process is a member of the group given as the group argument, then newcomm
is a communicator with group as its associated group. If the calling process
is not a member of group, e.g., group is MPI_GROUP_EMPTY, then the call is
a local operation and MPI_COMM_NULL is returned as newcomm.
MPI_Comm_create_group
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_group, can be used in subsequent calls to MPI_Comm_create_group
(or other communicator constructors) to further subdivide a computation
into parallel sub-computations. A more general service is provided by MPI_Comm_split.
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.
MPI_Comm_create
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