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NAME
MPI_Intercomm_create - Creates an intercommuncator from two intracommu-
nicators.
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Intercomm_create(MPI_Comm local_comm, int local_leader,
MPI_Comm peer_comm, int remote_leader, int tag, MPI_Comm *newintercomm)
Fortran Syntax
INCLUDE 'mpif.h'
MPI_INTERCOMM_CREATE(LOCAL_COMM, LOCAL_LEADER, PEER_COMM,
REMOTE_LEADER, TAG, NEWINTERCOMM, IERROR)
INTEGER LOCAL_COMM, LOCAL_LEADER, PEER_COMM, REMOTE_LEADER
INTEGER TAG, NEWINTERCOMM, IERROR
C++ Syntax
#include <mpi.h>
Intercomm Intracomm::Create_intercomm(int local_leader, const
Comm& peer_comm, int remote_leader, int tag) const
INPUT PARAMTERS
local_comm
The communicator containing the process that initiates the
inter-communication (handle).
local_leader
Rank of local group leader in local_comm (integer).
peer_comm "Peer" communicator; significant only at the local_leader
(handle).
remote_leader
Rank of remote group leader in peer_comm; significant only at
the local_leader (integer).
tag Message tag used to identify new intercommunicator (integer).
OUTPUT PARAMETERS
newintercomm
Created intercommunicator (handle).
IERROR Fortran only: Error status (integer).
DESCRIPTION
This call creates an intercommunicator. It is collective over the union
of the local and remote groups. Processes should provide identical
local_comm and local_leader arguments within each group. Wildcards are
not permitted for remote_leader, local_leader, and tag.
This call uses point-to-point communication with communicator
NOTES
We recommend using a dedicated peer communicator, such as a duplicate
of MPI_COMM_WORLD, to avoid trouble with peer communicators.
The MPI 1.1 Standard contains two mutually exclusive comments on the
input intracommunicators. One says that their repective groups must be
disjoint; the other that the leaders can be the same process. After
some discussion by the MPI Forum, it has been decided that the groups
must be disjoint. Note that the reason given for this in the standard
is not the reason for this choice; rather, the other operations on
intercommunicators (like MPI_Intercomm_merge ) do not make sense if the
groups are not disjoint.
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_Intercomm_merge
MPI_Comm_free
MPI_Comm_remote_group
MPI_Comm_remote_size
Open MPI 1.2 September 2006 MPI_Intercomm_create(3OpenMPI)
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