#define boxbod_N       6

#define boxbod_P       2

static double boxbod_x0a[boxbod_P] = { 1.0, 1.0 };

static double boxbod_x0b[boxbod_P] = { 100.0, 0.75 };

static double boxbod_epsrel = 1.0e-7;

static double boxbod_sigma[boxbod_P] = {

  1.2354515176E+01, 1.0455993237E-01

};

static double boxbod_X[boxbod_N] = { 1.0, 2.0, 3.0, 5.0, 7.0, 10.0 };

static double boxbod_F[boxbod_N] = { 109.0, 149.0, 149.0, 191.0,

                                     213.0, 224.0 };

static void

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

                 const double epsrel, const char *sname,

                 const char *pname)

{

  size_t i;

  const double sumsq_exact = 1.1680088766E+03;

  const double boxbod_x[boxbod_P] = { 2.1380940889E+02,

                                      5.4723748542E-01 };

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

               sname, pname);

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

    {

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

                   sname, pname, i);

    }

}

static int

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

{

  double b[boxbod_P];

  size_t i;

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

    {

      b[i] = gsl_vector_get(x, i);

    }

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

    {

      double xi = boxbod_X[i];

      double yi;

      yi = b[0] * (1.0 - exp(-b[1] * xi));

      gsl_vector_set (f, i, yi - boxbod_F[i]);

    }

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

  return GSL_SUCCESS;

}

static int

boxbod_df (const gsl_vector * x, void *params, gsl_matrix * df)

{

  double b[boxbod_P];

  size_t i;

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

    {

      b[i] = gsl_vector_get(x, i);

    }

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

    {

      double xi = boxbod_X[i];

      double term = exp(-b[1] * xi);

      gsl_matrix_set (df, i, 0, 1.0 - term);

      gsl_matrix_set (df, i, 1, b[0] * term * xi);

    }

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

  return GSL_SUCCESS;

}

static int

boxbod_fvv (const gsl_vector * x, const gsl_vector * v,

            void *params, gsl_vector * fvv)

{

  double x1 = gsl_vector_get(x, 0);

  double x2 = gsl_vector_get(x, 1);

  double v1 = gsl_vector_get(v, 0);

  double v2 = gsl_vector_get(v, 1);

  size_t i;

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

    {

      double ti = boxbod_X[i];

      double term = exp(-x2 * ti);

      gsl_vector_set(fvv, i, term * ti * v2 * (2*v1 - ti*v2*x1));

    }

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

  return GSL_SUCCESS;

}

static gsl_multifit_nlinear_fdf boxbod_func =

{

  boxbod_f,

  boxbod_df,

  boxbod_fvv,

  boxbod_N,

  boxbod_P,

  NULL,

  0,

  0,

  0

};

static test_fdf_problem boxboda_problem =

{

  "nist-boxboda",

  boxbod_x0a,

  NULL,

  boxbod_sigma,

  &boxbod_epsrel,

  &boxbod_checksol,

  &boxbod_func

};

static test_fdf_problem boxbodb_problem =

{

  "nist-boxbodb",

  boxbod_x0b,

  NULL,

  boxbod_sigma,

  &boxbod_epsrel,

  &boxbod_checksol,

  &boxbod_func

};