Topo_Cart* sub(const int remain_dims[], MPI_Comm* newcomm);
int coords(int rank, int maxdims, int coords[]);
int get(int maxdims, int* dims, int* periods, int* coords);
Topo_Cart* sub(const int remain_dims[], MPI_Comm* newcomm);
int coords(int rank, int maxdims, int coords[]);
int get(int maxdims, int* dims, int* periods, int* coords);