NAME

       MPI_Graph_create  -   Makes  a  new  communicator  to  which topology information has been
       attached

SYNOPSIS

       int MPI_Graph_create(MPI_Comm comm_old, int nnodes, const int indx[],
                            const int edges[], int reorder, MPI_Comm *comm_graph)

INPUT PARAMETERS

       comm_old
              - input communicator without topology (handle)
       nnodes - number of nodes in graph (integer)
       indx   - array of integers describing node degrees (see below)
       edges  - array of integers describing graph edges (see below)
       reorder
              - ranking may be reordered (true) or not (false) (logical)

OUTPUT PARAMETERS

       comm_graph
              - communicator with graph topology added (handle)

NOTES

       Each process must provide a description of the entire graph, not just the neigbors of  the
       calling process.

ALGORITHM

       We ignore the reorder info currently.

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.

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_TOPOLOGY
              - Invalid topology.  Either there is no topology associated with this communicator,
              or it is not the correct type (e.g., MPI_CART when expecting MPI_GRAPH ).
       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_ARG
              -  Invalid  argument.  Some argument is invalid and is not identified by a specific
              error class (e.g., MPI_ERR_RANK ).

                                            11/12/2016                        MPI_Graph_create(3)