/* nag_zero_nonlin_eqns_deriv_1 (c05ubc) Example Program.
 *
 * Copyright 1998 Numerical Algorithms Group.
 *
 * Mark 5, 1998.
 * Mark 7 revised, 2001.
 * Mark 8 revised, 2004.
 */

#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 f(Integer n, double x[], double fvec[], double fjac[],
                       Integer tdfjac, Integer *userflag, Nag_User *comm);
#ifdef __cplusplus
}
#endif

int main(int argc, char *argv[])
{
  FILE     *fpout;

  Integer  exit_status = 0, j, n = 9, tdfjac;
  NagError fail;
  Nag_User comm;
  double   *fjac = 0, *fvec = 0, *x = 0, xtol;

  INIT_FAIL(fail);

  /* Check for command-line IO options */
  fpout = nag_example_file_io(argc, argv, "-results", NULL);
  fprintf(fpout,
          "nag_zero_nonlin_eqns_deriv_1 (c05ubc) Example Program Results\n");
  if (n > 0)
    {
      if (!(fjac = NAG_ALLOC(n*n, double)) ||
          !(fvec = NAG_ALLOC(n, double)) ||
          !(x = NAG_ALLOC(n, double)))
        {
          fprintf(fpout, "Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      fprintf(fpout, "Invalid n.\n");
      exit_status = 1;
      return exit_status;
    }
  /* 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(X02AJC);
  tdfjac = n;
  /* nag_zero_nonlin_eqns_deriv_1 (c05ubc).
   * Solution of a system of nonlinear equations (using first
   * derivatives), thread-safe
   */
  nag_zero_nonlin_eqns_deriv_1(n, x, fvec, fjac, tdfjac, f, xtol, &comm, &fail);
  if (fail.code == NE_NOERROR)
    {
      fprintf(fpout, "Final approximate solution\n\n");
      for (j = 0; j < n; j++)
        fprintf(fpout, "%12.4f%s", x[j], (j%3 == 2 || j == n-1)?"\n":" ");
    }
  else
    {
      fprintf(fpout, "Error from nag_zero_nonlin_eqns_deriv_1 (c05ubc).\n%s\n",
              fail.message);
      if (fail.code == NE_TOO_MANY_FUNC_EVAL ||
          fail.code == NE_XTOL_TOO_SMALL ||
          fail.code == NE_NO_IMPROVEMENT)
        {
          fprintf(fpout, "Approximate solution\n\n");
          for (j = 0; j < n; j++)
            fprintf(fpout, "%12.4f%s", x[j], (j%3 == 2 || j == n-1)?"\n":" ");
        }
      exit_status = 2;
    }
 END:
  if (fpout != stdout) fclose(fpout);
  if (fjac) NAG_FREE(fjac);
  if (fvec) NAG_FREE(fvec);
  if (x) NAG_FREE(x);
  return exit_status;
}


static void NAG_CALL f(Integer n, double x[], double fvec[], double fjac[],
                       Integer tdfjac, Integer *userflag, Nag_User *comm)
{
#define FJAC(I, J) fjac[((I))*tdfjac+(J)]
  Integer j, k;

  if (*userflag != 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
    {
      for (k = 0; k < n; k++)
        {
          for (j = 0; j < n; j++)
            FJAC(k, j) = 0.0;
          FJAC(k, k) = 3.0 - x[k] * 4.0;
          if (k > 0)
            FJAC(k, k-1) = -1.0;
          if (k < n-1)
            FJAC(k, k+1) = -2.0;
        }
    }
}