void compute_tentative_velocity(float **u, float **v, float **f, float **g,
char **flag, int imax, int jmax, float del_t, float delx, float dely,
float gamma, float Re);
void compute_rhs(float **f, float **g, float **rhs, char **flag, int imax,
int jmax, float del_t, float delx, float dely);
int poisson(float **p, float **rhs, char **flag, int imax, int jmax,
float delx, float dely, float eps, int itermax, float omega,
float *res, int ifull);
void update_velocity(float **u, float **v, float **f, float **g, float **p,
char **flag, int imax, int jmax, float del_t, float delx, float dely);
void set_timestep_interval(float *del_t, int imax, int jmax, float delx,
float dely, float **u, float **v, float Re, float tau);