#include <stdio.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_math.h>

#include <gsl/gsl_min.h>

double fn1 (double x, void * params)

{

  (void)(params); /* avoid unused parameter warning */

  return cos(x) + 1.0;

}

int

main (void)

{

  int status;

  int iter = 0, max_iter = 100;

  const gsl_min_fminimizer_type *T;

  gsl_min_fminimizer *s;

  double m = 2.0, m_expected = M_PI;

  double a = 0.0, b = 6.0;

  gsl_function F;

  F.function = &fn1;

  F.params = 0;

  T = gsl_min_fminimizer_brent;

  s = gsl_min_fminimizer_alloc (T);

  gsl_min_fminimizer_set (s, &F, m, a, b);

  printf ("using %s method\n",

          gsl_min_fminimizer_name (s));

  printf ("%5s [%9s, %9s] %9s %10s %9s\n",

          "iter", "lower", "upper", "min",

          "err", "err(est)");

  printf ("%5d [%.7f, %.7f] %.7f %+.7f %.7f\n",

          iter, a, b,

          m, m - m_expected, b - a);

  do

    {

      iter++;

      status = gsl_min_fminimizer_iterate (s);

      m = gsl_min_fminimizer_x_minimum (s);

      a = gsl_min_fminimizer_x_lower (s);

      b = gsl_min_fminimizer_x_upper (s);

      status 

        = gsl_min_test_interval (a, b, 0.001, 0.0);

      if (status == GSL_SUCCESS)

        printf ("Converged:\n");

      printf ("%5d [%.7f, %.7f] "

              "%.7f %+.7f %.7f\n",

              iter, a, b,

              m, m - m_expected, b - a);

    }

  while (status == GSL_CONTINUE && iter < max_iter);

  gsl_min_fminimizer_free (s);

  return status;

}