NAME

       MPI_Cart_create  -  Makes  a  new communicator to which Cartesian topology information has
       been attached.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Cart_create(MPI_Comm comm_old, int ndims, const int dims[],
            const int periods[], int reorder, MPI_Comm *comm_cart)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_CART_CREATE(COMM_OLD, NDIMS, DIMS, PERIODS, REORDER,
                 COMM_CART, IERROR)
            INTEGER   COMM_OLD, NDIMS, DIMS(*), COMM_CART, IERROR
            LOGICAL   PERIODS(*), REORDER

C++ Syntax

       #include <mpi.h>
       Cartcomm Intracomm.Create_cart(int[] ndims, int[] dims[],
            const bool periods[], bool reorder) const

INPUT PARAMETERS

       comm_old  Input communicator (handle).

       ndims     Number of dimensions of Cartesian grid (integer).

       dims      Integer array  of  size  ndims  specifying  the  number  of  processes  in  each
                 dimension.

       periods   Logical  array  of  size ndims specifying whether the grid is periodic (true) or
                 not (false) in each dimension.

       reorder   Ranking may be reordered (true) or not (false) (logical).

OUTPUT PARAMETERS

       comm_cart Communicator with new Cartesian topology (handle).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Cart_create returns a handle to a new communicator to  which  the  Cartesian  topology
       information is attached. If reorder = false then the rank of each process in the new group
       is identical to its rank in the  old  group.  Otherwise,  the  function  may  reorder  the
       processes  (possibly  so  as  to  choose a good embedding of the virtual topology onto the
       physical machine). If the total size of the Cartesian grid is smaller than the size of the
       group   of   comm,   then  some  processes  are  returned  MPI_COMM_NULL,  in  analogy  to
       MPI_Comm_split. The call is erroneous if it specifies a grid that is larger than the group
       size.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and
       Fortran routines in the last argument. C++ functions do not return errors. If the  default
       error  handler  is  set  to  MPI::ERRORS_THROW_EXCEPTIONS, 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   MPI_Comm_set_errhandler;   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.