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MPI_Intercomm_merge(3) MPI MPI_Intercomm_merge(3)

NAME

MPI_Intercomm_merge - Creates an intracommuncator from an intercommunicator

SYNOPSIS



int MPI_Intercomm_merge(MPI_Comm intercomm, int high, MPI_Comm *newintracomm)










INPUT PARAMETERS



  

  
- inter-communicator (handle)

  

  
- ordering of the local and remote groups in the new intra-communicator
      (logical)
    

  








OUTPUT PARAMETERS



  

  
- new intra-communicator (handle)
    

  








NOTES


While all processes may provide the same value for the high
    parameter, this requires the MPI implementation to determine which group of
    processes should be ranked first.








THREAD AND INTERRUPT SAFETY


This routine is thread-safe. This means that this routine may be
    safely used by multiple threads without the need for any user-provided
    thread locks. However, the routine is not interrupt safe. Typically, this is
    due to the use of memory allocation routines such as malloc or other
    non-MPICH runtime routines that are themselves not interrupt-safe.








NOTES FOR FORTRAN


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 Fortran.








ALGORITHM


\neAllocate contexts \neLocal and remote group leaders swap high
    values \neDetermine the high value. \neMerge the two groups and make the
    intra-communicator










ERRORS


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. Before the value is returned, the current MPI
    error handler is called. By default, this error handler aborts the MPI job.
    The error handler may be changed with MPI_Comm_set_errhandler (for
    communicators), MPI_File_set_errhandler (for files), and
    MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine
    MPI_Errhandler_set may be used but its use is deprecated. 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; however, MPI implementations will
    attempt to continue whenever possible.





  

  
- No error; MPI routine completed successfully.

  

  
- Invalid argument. Some argument is invalid and is not identified by a
      specific error class (e.g., MPI_ERR_RANK ).

  

  
- Invalid communicator. A common error is to use a null communicator in a
      call (not even allowed in MPI_Comm_rank ).

  

  
- Other error; use MPI_Error_string to get more information about
      this error code.
    

  








SEE ALSO


MPI_Intercomm_create, MPI_Comm_free







  

    2/9/2024