MPIIntercommcreate(3OpenMPI) MPIIntercommcreate(3OpenMPI)

NAME
       MMPPIIIInntteerrccoommmmccrreeaattee - Creates an intercommuncator from two intracommu-
       nicators.


SSYYNNTTAAXX
CC SSyynnttaaxx
       #include 
       int MPIIntercommcreate(MPIComm localcomm, int localleader,
            MPIComm peercomm, int remoteleader, int tag, MPIComm *newintercomm)


FFoorrttrraann SSyynnttaaxx
       INCLUDE 'mpif.h'
       MPIINTERCOMMCREATE(LOCALCOMM, LOCALLEADER, PEERCOMM,
                 REMOTELEADER, TAG, NEWINTERCOMM, IERROR)
            INTEGER   LOCALCOMM, LOCALLEADER, PEERCOMM, REMOTELEADER
            INTEGER   TAG, NEWINTERCOMM, IERROR


CC++++ SSyynnttaaxx
       #include 
       Intercomm Intracomm::Createintercomm(int localleader, const
            Comm& peercomm, int remoteleader, int tag) const


IINNPPUUTT PPAARRAAMMTTEERRSS
       localcomm
                 The communicator containing the process  that  initiates  the
                 inter-communication (handle).

       localleader
                 Rank of local group leader in localcomm (integer).

       peercomm "Peer"  communicator;  significant  only  at the localleader
                 (handle).

       remoteleader
                 Rank of remote group leader in peercomm; significant only at
                 the localleader (integer).

       tag       Message tag used to identify new intercommunicator (integer).


OOUUTTPPUUTT PPAARRAAMMEETTEERRSS
       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
       localcomm and localleader arguments within each group. Wildcards  are
       not permitted for remoteleader, localleader, and tag.

       This   call   uses   point-to-point   communication  with  communicator
       peercomm, and with tag tag between the leaders.  Thus,  care  must  be
       taken  that  there  be no pending communication on peercomm that could
       interfere with this communication.

       If multiple MPIIntercommcreates are being made, they should use  dif-
       ferent  tags  (more  precisely,  they  should ensure that the local and
       remote leaders are using different tags for each MPIintercommcreate).


NNOOTTEESS
       We  recommend  using a dedicated peer communicator, such as a duplicate
       of MPICOMMWORLD, 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 rreeaassoonn given for this in the  standard
       is  nnoott  the  reason  for  this choice; rather, the ootthheerr operations on
       intercommunicators (like MPIIntercommmerge ) do not make sense if the
       groups are not disjoint.


EERRRROORRSS
       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::ERRORSTHROWEXCEPTIONS, 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
       MPICommseterrhandler; the predefined error handler MPIERRORSRETURN
       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
       MPIIntercommmerge
       MPICommfree
       MPICommremotegroup
       MPICommremotesize





Open MPI 1.2                    September 2006  MPIIntercommcreate(3OpenMPI)