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NAME

MPI_Cart_rank - Returns the rank corresponding to a given set of coordinates in the cartesian communicator

SYNOPSIS

#include <mpi.h> int MPI_Cart_rank(MPI_Comm comm , int *coords , int *rank );

#include <pmpi.h> int PMPI_Cart_rank(MPI_Comm comm , int *coords , int *rank );

#include <mpi.h> int MPI::Cartcomm::Get_cart_rank(const int *coords ) const;

INCLUDE 'mpif.h' MPI_CART_RANK(comm , coords , rank , ierr ) INTEGER comm , coords (*), rank , ierr

INPUT PARAMETERS

comm - cartesian communicator (handle)

coords - coordinates of requested rank (array)

OUTPUT PARAMETER

rank - the rank of the required process (integer).

DESCRIPTION

The MPI_Cart_rank() function is used to obtain the rank corresponding to a given set of coordinates, coords , within a cartesian communicator comm .

If a particular dimension is periodic, then the requested coordinate is wrapped inside the cartesian region. Otherwise, a coordinate lying outside the cartesian box will cause the error value MPI_ERR_ARG to be returned.

In C++, the return value is rank .

The communicator must be a valid one (not MPI_COMM_NULL). PMPI_Cart_rank() is the profiling version of this function.

ERRORS

All MPI routines except for MPI_Wtime and MPI_Wtick return an error code. The the current MPI error handler is invoked if the return value is not MPI_SUCCESS. The default error handler aborts, but this may be changed with by using the MPI_Errhandler_set() function. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. Note that MPI does not guarentee that an MPI program can continue past an error. In this implementation, all errors except MPI_ERR_INTERN or MPI_ERR_OTHER should always be recoverable.

In C, the error code is passed as the return value. In FORTRAN, all functions have an parameter ierr which returns the error code. MPI C++ functions do not directly return an error code. However, C++ users may want to use the MPI::ERRORS_THROW_EXCEPTIONS handler. This will throw an MPI::Exception with the corresponding error code. To prevent exceptions from being raised from within C and Fortran code, they will see all error return values as MPI_ERR_PENDING when this handler is chosen. In this implementation, call MPI::throw_exception() to throw the correct exception if this occurs.

MPI_SUCCESS - No error;

MPI_ERR_PENDING - Pending exception;

MPI_ERR_COMM - Invalid communicator;

MPI_ERR_TOPOLOGY - Not a cartesian communicator;

MPI_ERR_ARG - Invalid output pointer, or invalid coordinates.

SEE ALSO

MPI_Cart_create (3) MPI_Cartdim_get (3) MPI_Dims_create (3) MPI_Cart_get (3) MPI_Cart_coords (3) MPI_Cart_map (3)

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