int 

main(void)

{

  double par[5] = {1.0, 2.0, 10.0, 20.0, 30.0};

  const gsl_multimin_fminimizer_type *T = 

    gsl_multimin_fminimizer_nmsimplex2;

  gsl_multimin_fminimizer *s = NULL;

  gsl_vector *ss, *x;

  gsl_multimin_function minex_func;

  size_t iter = 0;

  int status;

  double size;

  /* Starting point */

  x = gsl_vector_alloc (2);

  gsl_vector_set (x, 0, 5.0);

  gsl_vector_set (x, 1, 7.0);

  /* Set initial step sizes to 1 */

  ss = gsl_vector_alloc (2);

  gsl_vector_set_all (ss, 1.0);

  /* Initialize method and iterate */

  minex_func.n = 2;

  minex_func.f = my_f;

  minex_func.params = par;

  s = gsl_multimin_fminimizer_alloc (T, 2);

  gsl_multimin_fminimizer_set (s, &minex_func, x, ss);

  do

    {

      iter++;

      status = gsl_multimin_fminimizer_iterate(s);

      if (status) 

        break;

      size = gsl_multimin_fminimizer_size (s);

      status = gsl_multimin_test_size (size, 1e-2);

      if (status == GSL_SUCCESS)

        {

          printf ("converged to minimum at\n");

        }

      printf ("%5d %10.3e %10.3e f() = %7.3f size = %.3f\n", 

              iter,

              gsl_vector_get (s->x, 0), 

              gsl_vector_get (s->x, 1), 

              s->fval, size);

    }

  while (status == GSL_CONTINUE && iter < 100);

  gsl_vector_free(x);

  gsl_vector_free(ss);

  gsl_multimin_fminimizer_free (s);

  return status;

}