/* nag_ode_ivp_adams_interp (d02qzc) Example Program.
 *
 * Copyright 1991 Numerical Algorithms Group.
 *
 * Mark 2, 1991.
 * Mark 6 revised, 2000.
 * Mark 7 revised, 2001.
 * Mark 8 revised, 2004.
 *
 */

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nagd02.h>
#include <nagx01.h>

#ifdef __cplusplus
extern "C" {
#endif
static void NAG_CALL ftry03(Integer neqf, double x, const double y[], double yp[],
                            Nag_User *comm);
#ifdef __cplusplus
}
#endif

#define NEQF   2
#define TSTART 0.0

int main(void)
{
  Nag_Boolean   alter_g, crit, one_step, sophist, vectol;
  Integer       exit_status = 0, i, j, max_step, neqf, neqg, nwant;
  NagError      fail;
  Nag_ODE_Adams opt;
  Nag_Start     state;
  double        *atol = 0, hmax, pi, *rtol = 0, t, tcrit, tinc, tout, twant,
  *y = 0;
  double        *ypwant = 0, *ywant = 0;

  INIT_FAIL(fail);

  printf("nag_ode_ivp_adams_interp (d02qzc) Example Program Results\n");
  /* nag_pi (x01aac).
   * pi
   */
  pi = nag_pi;
  state = Nag_NewStart;
  neqf = NEQF;
  if (neqf >= 1)
    {
      if (!(atol = NAG_ALLOC(neqf, double)) ||
          !(rtol = NAG_ALLOC(neqf, double)) ||
          !(y = NAG_ALLOC(neqf, double)) ||
          !(ywant = NAG_ALLOC(neqf, double)) ||
          !(ypwant = NAG_ALLOC(neqf, double)))
        {
          printf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      exit_status = 1;
      return exit_status;
    }


  neqg = 0;
  sophist = Nag_FALSE;
  vectol = Nag_TRUE;
  for (i = 0; i < 2; ++i)
    {
      atol[i] = 1e-08;
      rtol[i] = 0.0001;
    }
  one_step = Nag_TRUE;
  crit = Nag_TRUE;
  tinc = pi * 0.0625;
  tcrit = tinc * 8.0;
  tout = tcrit;
  max_step = 500;
  hmax = 2.0;
  t = TSTART;
  twant = TSTART + tinc;
  nwant = 2;
  y[0] = 0.0;
  y[1] = 1.0;
  printf("\n   T        Y(1)    Y(2)\n");
  printf(" %6.4f   %7.4f %7.4f  \n", t, y[0], y[1]);

  /* nag_ode_ivp_adams_setup (d02qwc).
   * Setup function for nag_ode_ivp_adams_roots (d02qfc)
   */
  nag_ode_ivp_adams_setup(&state, neqf, vectol, atol, rtol, one_step, crit,
                          tcrit, hmax, max_step, neqg, &alter_g, sophist, &opt,
                          &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_ode_ivp_adams_setup (d02qwc).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }

  j = 1;

  while (t < tout && fail.code == NE_NOERROR)
    {
      /* nag_ode_ivp_adams_roots (d02qfc).
       * Ordinary differential equation solver using Adams method
       * (sophisticated use)
       */
      nag_ode_ivp_adams_roots(neqf, ftry03, &t, y, tout, NULLDFN,
                              NAGUSER_DEFAULT, &opt, &fail);
      if (fail.code != NE_NOERROR)
        {
          printf("Error from nag_ode_ivp_adams_roots (d02qfc).\n%s\n",
                  fail.message);
          exit_status = 1;
          goto END;
        }

      while (twant <= t && fail.code == NE_NOERROR)
        {
          /* nag_ode_ivp_adams_interp (d02qzc).
           * Interpolation function for use with
           * nag_ode_ivp_adams_roots (d02qfc)
           */
          nag_ode_ivp_adams_interp(neqf, twant, nwant, ywant, ypwant, &opt,
                                   &fail);
          if (fail.code != NE_NOERROR)
            {
              printf(
                      "Error from nag_ode_ivp_adams_interp (d02qzc).\n%s\n",
                      fail.message);
              exit_status = 1;
              goto END;
            }

          printf(" %6.4f   %7.4f %7.4f  \n", twant, ywant[0], ywant[1]);
          ++j;
          twant = (double) j*tinc + 0.0;
        }
    }
  /* Free the memory which was allocated by
   * nag_ode_ivp_adams_setup (d02qwc) to the pointers inside opt.
   */
  /* nag_ode_ivp_adams_free (d02qyc).
   * Freeing function for use with nag_ode_ivp_adams_roots
   * (d02qfc)
   */
  nag_ode_ivp_adams_free(&opt);

 END:
  if (atol) NAG_FREE(atol);
  if (rtol) NAG_FREE(rtol);
  if (y) NAG_FREE(y);
  if (ywant) NAG_FREE(ywant);
  if (ypwant) NAG_FREE(ypwant);
  return exit_status;
}


static void NAG_CALL ftry03(Integer neqf, double x, const double y[], double
                            yp[], Nag_User *comm)
{
  yp[0] = y[1];
  yp[1] = -y[0];
}                               /* ftry03 */