bionic (3) MPI_Intercomm_merge.3.gz

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

       intercomm
              - Intercommunicator (handle)
       high   -  Used  to  order the groups within comm (logical) when creating the new communicator.  This is a
              boolean value; the group that sets high true has its processes ordered after the group  that  sets
              this value to false.  If all processes in the intercommunicator provide the same value, the choice
              of which group is ordered first is arbitrary.

OUTPUT PARAMETERS

       newintracomm
              - Created intracommunicator (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 guarentee that an MPI program can continue past an error; however, MPI
       implementations will attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_COMM
              - Invalid communicator.  A common error is to use a null communicator in a call (not even  allowed
              in MPI_Comm_rank ).
       MPI_ERR_INTERN
              - This error is returned when some part of the MPICH implementation is unable to acquire memory.

SEE ALSO

       MPI_Intercomm_create, MPI_Comm_free

                                                   11/12/2016                             MPI_Intercomm_merge(3)