void
test_f (const gsl_root_fsolver_type * T, const char * description, gsl_function *f,
double lower_bound, double upper_bound, double correct_root)
{
int status;
size_t iterations = 0;
double r, a, b;
double x_lower, x_upper;
gsl_root_fsolver * s;
x_lower = lower_bound;
x_upper = upper_bound;
s = gsl_root_fsolver_alloc(T);
gsl_root_fsolver_set(s, f, x_lower, x_upper) ;
do
{
iterations++ ;
gsl_root_fsolver_iterate (s);
r = gsl_root_fsolver_root(s);
a = gsl_root_fsolver_x_lower(s);
b = gsl_root_fsolver_x_upper(s);
if (a > b)
gsl_test (GSL_FAILURE, "interval is invalid (%g,%g)", a, b);
if (r < a || r > b)
gsl_test (GSL_FAILURE, "r lies outside interval %g (%g,%g)", r, a, b);
status = gsl_root_test_interval (a,b, EPSABS, EPSREL);
}
while (status == GSL_CONTINUE && iterations < MAX_ITERATIONS);
gsl_test (status, "%s, %s (%g obs vs %g expected) ",
gsl_root_fsolver_name(s), description,
gsl_root_fsolver_root(s), correct_root);
if (iterations == MAX_ITERATIONS)
{
gsl_test (GSL_FAILURE, "exceeded maximum number of iterations");
}
/* check the validity of the returned result */
if (!WITHIN_TOL (r, correct_root, EPSREL, EPSABS))
{
gsl_test (GSL_FAILURE, "incorrect precision (%g obs vs %g expected)",
r, correct_root);
}
gsl_root_fsolver_free(s);
}
int
main (void)
{
int status;
int iter = 0, max_iter = 100;
const gsl_root_fsolver_type *T;
gsl_root_fsolver *s;
double r = 0, r_expected = sqrt (5.0);
double x_lo = 0.0, x_hi = 5.0;
gsl_function F;
struct quadratic_params params = {1.0, 0.0, -5.0};
F.function = &quadratic;
F.params = ¶ms;
T = gsl_root_fsolver_brent;
s = gsl_root_fsolver_alloc (T);
gsl_root_fsolver_set (s, &F, x_lo, x_hi);
printf ("using %s method\n",
gsl_root_fsolver_name (s));
printf ("%5s [%9s, %9s] %9s %10s %9s\n",
"iter", "lower", "upper", "root",
"err", "err(est)");
do
{
iter++;
status = gsl_root_fsolver_iterate (s);
r = gsl_root_fsolver_root (s);
x_lo = gsl_root_fsolver_x_lower (s);
x_hi = gsl_root_fsolver_x_upper (s);
status = gsl_root_test_interval (x_lo, x_hi,
0, 0.001);
if (status == GSL_SUCCESS)
printf ("Converged:\n");
printf ("%5d [%.7f, %.7f] %.7f %+.7f %.7f\n",
iter, x_lo, x_hi,
r, r - r_expected,
x_hi - x_lo);
}
while (status == GSL_CONTINUE && iter < max_iter);
gsl_root_fsolver_free (s);
return status;
}
int
main ()
{
int status;
int iterations = 0, max_iterations = 100;
gsl_root_fsolver *s;
double r = 0, r_expected = sqrt (5.0);
double x_lower x = 0.0, x_upper = 5.0;
gsl_function F;
struct quadratic_params params =
{1.0, 0.0, -5.0};
F.function = &quadratic;
F.params = ¶ms;
s = gsl_root_fsolver_alloc (gsl_root_fsolver_bisection);
gsl_root_fsolver_set (s, &F, x);
printf ("using %s method\n", gsl_root_fsolver_name (s));
printf ("%5s [%9s, %9s] %9s %9s %10s %9s\n",
"iter", "lower", "upper", "root", "actual", "err", "err(est)");
do
{
iterations++;
status = gsl_root_fsolver_iterate (s);
r = gsl_root_fsolver_root (s);
x_lower = gsl_root_fsolver_x_lower (s);
x_upper = gsl_root_fsolver_x_upper (s);
status = gsl_root_test_interval (x, 0, 0.001);
if (status == GSL_SUCCESS)
printf ("Converged:\n");
printf ("%5d [%.7f, %.7f] %.7f %.7f %+.7f %.7f\n",
iterations, x_lower, x_upper,
r, r_expected, r - r_expected, x_upper - x_lower);
}
while (status == GSL_CONTINUE && iterations < max_iterations);
}
void
test_f_e (const gsl_root_fsolver_type * T,
const char * description, gsl_function *f,
double lower_bound, double upper_bound, double correct_root)
{
int status;
size_t iterations = 0;
double x_lower, x_upper;
gsl_root_fsolver * s;
x_lower = lower_bound;
x_upper = upper_bound;
s = gsl_root_fsolver_alloc(T);
status = gsl_root_fsolver_set(s, f, x_lower, x_upper) ;
gsl_test (status != GSL_EINVAL, "%s (set), %s", T->name, description);
if (status == GSL_EINVAL)
{
gsl_root_fsolver_free(s);
return ;
}
do
{
iterations++ ;
gsl_root_fsolver_iterate (s);
x_lower = gsl_root_fsolver_x_lower(s);
x_upper = gsl_root_fsolver_x_lower(s);
status = gsl_root_test_interval (x_lower, x_upper,
EPSABS, EPSREL);
}
while (status == GSL_CONTINUE && iterations < MAX_ITERATIONS);
gsl_test (!status, "%s, %s", gsl_root_fsolver_name(s), description,
gsl_root_fsolver_root(s) - correct_root);
gsl_root_fsolver_free(s);
}
int calcola_equilibrio(double cost_Hamaker, double cost_Debye_quadra, double* risultato) {
// da esempio: http://www.gnu.org/software/gsl/manual/html_node/Root-Finding-Examples.html
int status;
int iter = 0, max_iter = 100;
const gsl_root_fsolver_type *T;
gsl_root_fsolver *s;
double r = 0;
double x_lo = 1E-10, x_hi = 8E-9;
gsl_function F;
params parametri = {cost_Hamaker, cost_Debye_quadra, in.sigma, in.D_me, in.teta};
F.function = &funzione_equilibrio;
F.params = ¶metri;
//T = gsl_root_fsolver_brent;
T = gsl_root_fsolver_bisection;
s = gsl_root_fsolver_alloc (T);
gsl_root_fsolver_set (s, &F, x_lo, x_hi);
#ifdef DEBUG_ROOT
printf ("using %s method\n",
gsl_root_fsolver_name (s));
printf ("%5s [%12s, %12s] %12s %12s\n",
"iter", "lower", "upper", "root", "err(est)");
#endif
do
{
iter++;
status = gsl_root_fsolver_iterate (s);
r = gsl_root_fsolver_root (s);
x_lo = gsl_root_fsolver_x_lower (s);
x_hi = gsl_root_fsolver_x_upper (s);
status = gsl_root_test_interval (x_lo, x_hi,
0, 0.001);
// controllo su dimensione minima
if(x_hi < in.D_min){
*risultato = in.D_min;
#ifdef DEBUG_ROOT
printf ("limite superiore= %e < %e=minimo consentito\n",x_hi,in.D_min);
#endif
gsl_root_fsolver_free (s);
return GSL_SUCCESS;
}
#ifdef DEBUG_ROOT
if (status == GSL_SUCCESS)
printf ("Converged:\n");
printf ("%5d [%e, %e] %e %e\n",
iter, x_lo, x_hi,
r,
x_hi - x_lo);
#endif
}
while (status == GSL_CONTINUE && iter < max_iter);
gsl_root_fsolver_free (s);
*risultato = r;
return status;
}
static VALUE rb_gsl_fsolver_name(VALUE obj)
{
gsl_root_fsolver *s = NULL;
Data_Get_Struct(obj, gsl_root_fsolver, s);
return rb_str_new2(gsl_root_fsolver_name(s));
}
