# Name

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

# Syntax

## C Syntax

```c
#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

```fortran
USE MPI
! or the older form: 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
```

## Fortran 2008 Syntax

```fortran
USE mpi_f08

MPI_Cart_create(comm_old, ndims, dims, periods, reorder, comm_cart, ierror)
    TYPE(MPI_Comm), INTENT(IN) :: comm_old
    INTEGER, INTENT(IN) :: ndims, dims(ndims)
    LOGICAL, INTENT(IN) :: periods(ndims), reorder
    TYPE(MPI_Comm), INTENT(OUT) :: comm_cart
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```


# 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.
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.