/* nag_zero_nonlin_eqns_deriv_rcomm (c05rdc) Example Program.
 *
 * Copyright 2011 Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */

#include <nag.h>
#include <nagx04.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <math.h>
#include <nagc05.h>
#include <nagx02.h>

#ifdef __cplusplus
extern "C" {
#endif
  static void NAG_CALL fcn(Integer n, const double x[], double fvec[],
                           double fjac[], Integer irevcm);
#ifdef __cplusplus
}
#endif

int main(void)
{

  Integer  exit_status = 0, i, j, n = 9, irevcm;
  NagError fail;
  Nag_ScaleType scale_mode;
  double   *diag = 0, *fjac = 0, *fvec = 0, *qtf = 0, *r = 0, *x = 0,
           *rwsav = 0;
  Integer  *iwsav = 0;
  double   factor, xtol;

  INIT_FAIL(fail);

  printf("nag_zero_nonlin_eqns_deriv_rcomm (c05rdc) Example Program Results\n");
  if (n > 0)
    {
      if (!(diag = NAG_ALLOC(n, double)) ||
          !(fjac = NAG_ALLOC(n*n, double)) ||
          !(fvec = NAG_ALLOC(n, double)) ||
          !(qtf = NAG_ALLOC(n, double)) ||
          !(r = NAG_ALLOC(n*(n+1)/2, double)) ||
          !(x = NAG_ALLOC(n, double)) ||
          !(iwsav = NAG_ALLOC(17, Integer)) ||
          !(rwsav = NAG_ALLOC(4*n + 10, double)))
        {
          printf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      printf("Invalid n.\n");
      exit_status = 1;
      goto END;
    }

  /* The following starting values provide a rough solution. */
  for (j = 0; j < n; j++)
    x[j] = -1.0;

  /* nag_machine_precision (x02ajc).
   * The machine precision
   */
  xtol = sqrt(nag_machine_precision);

  for (j = 0; j < n; j++)
    diag[j] = 1.0;

  scale_mode = Nag_ScaleProvided;
  factor = 100.0;
  irevcm = 0;

  /* nag_zero_nonlin_eqns_deriv_rcomm (c05rdc).
   * Solution of a system of nonlinear equations (function values only,
   * reverse communication)
   */

  do
    {
      nag_zero_nonlin_eqns_deriv_rcomm(&irevcm, n, x, fvec, fjac, xtol,
                                       scale_mode, diag, factor, r, qtf, iwsav,
                                       rwsav, &fail);

      switch (irevcm)
        {
        case 1:
          /* x and fvec are available for printing */
          break;
        case 2:
        case 3:
          fcn(n, x, fvec, fjac, irevcm);
          break;
        }

    } while (irevcm != 0);

  if (fail.code == NE_NOERROR)
    {
      printf("Final approximate solution\n\n");
      for (j = 0; j < n; j++)
        printf("%12.4f%s", x[j], (j%3 == 2 || j == n-1)?"\n":" ");
    }
  else
    {
      printf("Error from nag_zero_nonlin_eqns_deriv_rcomm (c05rdc).\n%s\n",
             fail.message);
      if (fail.code == NE_TOO_SMALL ||
          fail.code == NE_NO_IMPROVEMENT)
        {
          printf("Approximate solution\n\n");
          for (i = 0; i < n;  i++)
            printf("%12.4f%s", x[i], (i%3 == 2 || i == n-1)?"\n":" ");
          exit_status = 2;
        }
    }
 END:
  if (diag) NAG_FREE(diag);
  if (fjac) NAG_FREE(fjac);
  if (fvec) NAG_FREE(fvec);
  if (qtf) NAG_FREE(qtf);
  if (r) NAG_FREE(r);
  if (x) NAG_FREE(x);
  if (iwsav) NAG_FREE(iwsav);
  if (rwsav) NAG_FREE(rwsav);
  return exit_status;
}
static void NAG_CALL fcn(Integer n, const double x[], double fvec[],
                         double fjac[], Integer irevcm)
{
  Integer j, k;

  if (irevcm == 2)
    {
      for (k = 0; k < n; k++)
        {
          fvec[k] = (3.0-x[k]*2.0) * x[k] + 1.0;
          if (k > 0) fvec[k] -= x[k-1];
          if (k < n-1) fvec[k] -= x[k+1] * 2.0;
        }
    }
  else if (irevcm == 3)
    {
      for (k = 0; k < n; k++)
        {
          for (j = 0; j < n; j++)
            fjac[j*n + k] = 0.0;
          fjac[k*n + k] = 3.0 - x[k] * 4.0;
          if (k > 0)
            fjac[(k-1)*n + k] = -1.0;
          if (k < n-1)
            fjac[(k+1)*n + k] = -2.0;
        }
    }
}