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       MPI_Intercomm_create   -    Creates   an   intercommuncator   from  two


       #include <mpi.h>
       int MPI_Intercomm_create(MPI_Comm lcomm, int lleader,
                              MPI_Comm pcomm, int pleader, int tag,
                              MPI_Comm *newcomm)


       lcomm  - Local (intra)communicator
              - Rank in local_comm of leader (often 0)
       pcomm  - Remote communicator
              - Rank in peer_comm of remote leader (often 0)
       tag    - Message tag  to  use  in  constructing  intercommunicator;  if
              multiple  MPI_Intercomm_creates  are being made, they should use
              different tags (more precisely, ensure that the local and remote
              leaders  are  using different tags for each MPI_intercomm_create


              - Created intercommunicator


       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.


       All  MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
       an additional argument ierr at the end of the argument list.   ierr  is
       an  integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are  invoked  with
       the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in


       If an error occurs in an MPI function, the current MPI error handler is
       called  to  handle  it.   By default, this error handler aborts the MPI
       job.  The error handler may be changed with  MPI_Errhandler_set  ;  the
       predefined  error  handler MPI_ERRORS_RETURN may be used to cause error
       values to be returned (in C and Fortran; this  error  handler  is  less
       useful  in  with  the  C++  MPI bindings.  The predefined error handler
       MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the  error  value
       needs  to  be recovered).  Note that MPI does not guarantee that an MPI
       program can continue past an error.

       All MPI routines (except MPI_Wtime and  MPI_Wtick  )  return  an  error
       value;  C routines as the value of the function and Fortran routines in
       the last argument.  The C++  bindings  for  MPI  do  not  return  error
       values;  instead,  error values are communicated by throwing exceptions
       of type MPI::Exception (but  not  by  default).   Exceptions  are  only
       thrown if the error value is not MPI::SUCCESS .

       Note  that  if  the MPI::ERRORS_RETURN handler is set in C++, while MPI
       functions will return upon an error, there will be no  way  to  recover
       what the actual error value was.
              - No error; MPI routine completed successfully.
              -  Invalid  communicator.   A  common  error  is  to  use a null
              communicator in a call (not even allowed in MPI_Comm_rank ).
              - Invalid tag argument.  Tags must be non-negative;  tags  in  a
              receive  ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.)  may also
              be MPI_ANY_TAG .  The largest tag value is available through the
              the attribute MPI_TAG_UB .

              -  Invalid  argument.   Some  argument  is  invalid  and  is not
              identified by a specific error class.  This is typically a  NULL
              pointer or other such error.
              -  This  error  is  returned  when  some  part  of  the  LAM/MPI
              implementation is unable to acquire memory.
              - Invalid source or destination rank.   Ranks  must  be  between
              zero  and  the  size  of  the communicator minus one; ranks in a
              receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.)  may  also
              be MPI_ANY_SOURCE .


       MPI_Intercomm_merge, MPI_Comm_free, MPI_Comm_remote_group,


       For more information, please see the official MPI Forum web site, which
       contains the text  of  both  the  MPI-1  and  MPI-2  standards.   These
       documents contain detailed information about each MPI function (most of
       which is not duplicated in these man pages).


       The LAM Team would like the thank the MPICH Team for the handy  program
       to        generate        man        pages        ("doctext"       from    ),    the     initial
       formatting, and some initial text for most of the MPI-1 man pages.