# Name

`MPI_Cart_rank` - Determines process rank in communicator given
Cartesian location.

# Syntax

## C Syntax

```c
#include <mpi.h>

int MPI_Cart_rank(MPI_Comm comm, int coords[], int *rank)
```

## Fortran Syntax

```fortran
USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_CART_RANK(COMM, COORDS, RANK, IERROR)
    INTEGER	COMM, COORDS(*), RANK, IERROR
```

## Fortran 2008 Syntax

```fortran
USE mpi_f08

MPI_Cart_rank(comm, coords, rank, ierror)
    TYPE(MPI_Comm), INTENT(IN) :: comm
    INTEGER, INTENT(IN) :: coords(*)
    INTEGER, INTENT(OUT) :: rank
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```

# Input Parameters

* `comm` : Communicator with Cartesian structure (handle).
* `coords` : Integer array (of size ndims, which was defined by `MPI_Cart_create`
call) specifying the Cartesian coordinates of a process.

# Output Parameter

* `rank` : Rank of specified process (integer).
* `IERROR` : Fortran only: Error status (integer).

# Description

For a process group with Cartesian structure, the function `MPI_Cart_rank`
translates the logical process coordinates to process `rank`s as they are
used by the point-to-point routines. For dimension i with periods(i) =
true, if the coordinate, `coords(i)`, is out of range, that is, `coords(i)`
< 0 or `coords(i)` >= `dims(i)`, it is shifted back to the interval 0 =<
`coords(i)` < `dims(i)` automatically. Out-of-range coordinates are
erroneous for nonperiodic dimensions.

# 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.

# See Also

[`MPI_Cart_create`(3)](MPI_Cart_create.html)