int
gsl_odeiv2_driver_apply_fixed_step (gsl_odeiv2_driver * d, double *t,
const double h, const unsigned long int n,
double y[])
{
/* Alternative driver function that evolves the system from t using
* n steps of size h. In the beginning vector y contains the values
* of dependent variables at t. This function returns values at t =
* t + n * h in y. In case of an unrecoverable error, y and t
* contains the values after the last successful step.
*/
unsigned long int i;
d->n = 0;
/* Evolution loop */
for (i = 0; i < n; i++)
{
int s = gsl_odeiv2_evolve_apply_fixed_step (d->e, d->c, d->s, d->sys,
t, h, y);
if (s != GSL_SUCCESS)
{
return s;
}
d->n++;
}
return GSL_SUCCESS;
}
double dodes(double initial_value, double start_time, double end_time, \
int (*ode_function), char *solver_type, double nequs, double eps_abs, \
double eps_rel, double step_size, int *params)
{
double out = 0, t = 0;
//int status;
out = initial_value;
t = start_time;
//Setup ODE related parameters
gsl_odeiv2_system sys = {ode_function, NULL, nequs, NULL};
gsl_odeiv2_step *s = gsl_odeiv2_step_alloc (gsl_odeiv2_step_rkf45, nequs);
gsl_odeiv2_control *c = gsl_odeiv2_control_y_new (eps_abs, eps_rel);
gsl_odeiv2_evolve *e = gsl_odeiv2_evolve_alloc (nequs);
while(t < end_time)
{
gsl_odeiv2_evolve_apply_fixed_step (e, c, s, &sys, &t, step_size, &out);
}
gsl_odeiv2_evolve_free (e);
gsl_odeiv2_control_free (c);
gsl_odeiv2_step_free (s);
return out;
}
void dodea(double *initial_value, double start_time, double end_time, \
int (*ode_function), char *solver_type, double nequs, double eps_abs, \
double eps_rel, double step_size, int *params, double *out)
{
double t = start_time;
gsl_odeiv2_step_type *step_type;
/*Initialise output to initial state*/
int counter = 0;
for (counter = 0; counter<nequs;counter++)
{
out[counter] = initial_value[counter];
}
/*Setup ODE related parameters*/
gsl_odeiv2_system sys = {ode_function, NULL, nequs, params};
/*Select step solver*/
if (solver_type == "adams")
step_type = gsl_odeiv2_step_msadams;
if (solver_type == "stiff")
step_type = gsl_odeiv2_step_msbdf;
if (solver_type == "rk")
step_type = gsl_odeiv2_step_rk4;
if (solver_type == "rkf")
step_type = gsl_odeiv2_step_rkf45;
if (solver_type == "root")
step_type = gsl_odeiv2_step_rkck;
if (solver_type == "discrete")
step_type = gsl_odeiv2_step_rk8pd;
else
step_type = gsl_odeiv2_step_rkf45;
gsl_odeiv2_step *s = gsl_odeiv2_step_alloc (step_type, nequs);
gsl_odeiv2_control *c = gsl_odeiv2_control_y_new (eps_abs, eps_rel);
gsl_odeiv2_evolve *e = gsl_odeiv2_evolve_alloc (nequs);
while(t < end_time)
{
gsl_odeiv2_evolve_apply_fixed_step (e, c, s, &sys, &t, step_size, out);
}
gsl_odeiv2_evolve_free (e);
gsl_odeiv2_control_free (c);
gsl_odeiv2_step_free (s);
}
