#define rosenbrock_N         2

#define rosenbrock_P         2

#define rosenbrock_NTRIES    4

static double rosenbrock_x0[rosenbrock_P] = { -1.2, 1.0 };

static double rosenbrock_epsrel = 1.0e-12;

static void

rosenbrock_checksol(const double x[], const double sumsq,

                    const double epsrel, const char *sname,

                    const char *pname)

{

  size_t i;

  const double sumsq_exact = 0.0;

  gsl_test_rel(sumsq, sumsq_exact, epsrel, "%s/%s sumsq",

               sname, pname);

  for (i = 0; i < rosenbrock_P; ++i)

    {

      gsl_test_rel(x[i], 1.0, epsrel, "%s/%s i=%zu",

                   sname, pname, i);

    }

}

static int

rosenbrock_f (const gsl_vector * x, void *params, gsl_vector * f)

{

  double x1 = gsl_vector_get(x, 0);

  double x2 = gsl_vector_get(x, 1);

  gsl_vector_set(f, 0, 10.0 * (x2 - x1*x1));

  gsl_vector_set(f, 1, 1.0 - x1);

  return GSL_SUCCESS;

}

static int

rosenbrock_df (const gsl_vector * x, void *params, gsl_matrix * J)

{

  double x1 = gsl_vector_get(x, 0);

  gsl_matrix_set(J, 0, 0, -20.0*x1);

  gsl_matrix_set(J, 0, 1, 10.0);

  gsl_matrix_set(J, 1, 0, -1.0);

  gsl_matrix_set(J, 1, 1, 0.0);

  return GSL_SUCCESS;

}

static gsl_multifit_function_fdf rosenbrock_func =

{

  &rosenbrock_f,

  &rosenbrock_df,

  NULL,

  rosenbrock_N,

  rosenbrock_P,

  NULL,

  0,

  0

};

static test_fdf_problem rosenbrock_problem =

{

  "rosenbrock",

  rosenbrock_x0,

  NULL,

  &rosenbrock_epsrel,

  rosenbrock_NTRIES,

  &rosenbrock_checksol,

  &rosenbrock_func

};