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MPI_Intercomm_create - Creates an intercommunicator from two intracommunicators.
#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)
USE MPI
! or the older form: 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
USE mpi_f08
MPI_Intercomm_create(local_comm, local_leader, peer_comm, remote_leader,
tag, newintercomm, ierror)
TYPE(MPI_Comm), INTENT(IN) :: local_comm, peer_comm
INTEGER, INTENT(IN) :: local_leader, remote_leader, tag
TYPE(MPI_Comm), INTENT(OUT) :: newintercomm
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- 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).
- newintercomm
- Created intercommunicator (handle).
- IERROR
- Fortran only: Error status (integer).
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 peer_comm, and with tag tag between the
leaders. Thus, care must be taken that there be no pending communication
on peer_comm that could interfere with this communication.
If multiple
MPI_Intercomm_creates are being made, they should use different tags (more
precisely, they should ensure that the local and remote leaders are using
different tags for each MPI_intercomm_create).
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 respective 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.
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.
MPI_Intercomm_merge
MPI_Comm_free
MPI_Comm_remote_group
MPI_Comm_remote_size
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