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

int MPI_Cart_shift (MPI_Comm comm, int direction, int disp, int *rank_source, int *rank_dest);

int MPI_Graph_neighbors (MPI_Comm comm, int rank, int maxneighbors, int neighbors []);

int MPI_Dist_graph_neighbors (
    MPI_Comm comm,
    int maxindegree, int sources [], int sourceweights [],
    int maxoutdegree, int destinations [], int destweights []);