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MPI_Cart_create(3OpenMPI)                                                          MPI_Cart_create(3OpenMPI)



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, int *dims,
            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, const 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.




Open MPI 1.2                                   September 2006                      MPI_Cart_create(3OpenMPI)