# MPI_Cart_rank

Determines process rank in communicator given Cartesian location

## Synopsis

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

## Input Parameters

comm
  communicator with cartesian structure (handle)
coords
  integer array (of size `ndims`, the number of dimensions of the Cartesian topology associated with `comm`) specifying the cartesian coordinates of a process

## Output Parameters

rank
  rank of specified process (integer)

## Notes

Out-of-range coordinates are erroneous for non-periodic dimensions. Versions of MPICH before 1.2.2 returned `MPI_PROC_NULL` for the rank in this case.

## Thread and Interrupt Safety

This routine is both thread- and interrupt-safe. This means that this routine may safely be used by multiple threads and from within a signal handler.

## 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 guarantee 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_RANK
  Invalid source or destination rank. Ranks must be between zero and the size of the communicator minus one; ranks in a receive (`MPI_Recv`, `MPI_Irecv`, `MPI_Sendrecv`, etc.) may also be `MPI_ANY_SOURCE`.

MPI_ERR_ARG
  Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., `MPI_ERR_RANK`).