/* nag_check_deriv_1 (c05zcc) Example Program.
 *
 * Copyright 1998 Numerical Algorithms Group.
 *
 * Mark 5, 1998.
 * Mark 7 revised, 2001.
 * Mark 8 revised, 2004.
 */

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nagc05.h>

#ifdef __cplusplus
extern "C" {
#endif
  static void f(Integer n, double xc[], double fvecc[],
                double fjacc[], Integer tdj, Integer *userflag, Nag_User *comm);
#ifdef __cplusplus
}
#endif

int main(void)
{

#define FJAC(I,J) fjac[(I)*tdfjac + J]

  Integer exit_status=0, i, j, n, tdfjac;
  NagError fail;
  Nag_User comm;
  double *fjac=0, *fvec=0, *x=0;
  INIT_FAIL(fail);


  Vprintf("nag_check_deriv_1 (c05zcc) Example Program Results\n");
  n = 3;
  if (n>0)
    {
      if ( !( fjac = NAG_ALLOC(n*n, double)) ||
           !( fvec = NAG_ALLOC(n, double)) ||
           !( x = NAG_ALLOC(n, double)) )
        {
          Vprintf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
      tdfjac = n;
    }
  else
    {
      Vprintf("Invalid n.\n");
      exit_status = 1;
      return exit_status;
    }

  /* Set up an arbitrary point at which to check the 1st derivatives */
  x[0] = 9.2e-01;
  x[1] = 1.3e-01;
  x[2] = 5.4e-01;
  Vprintf("The test point is ");
  for (j=0; j<n; ++j)
    Vprintf("%13.3e", x[j]);
  Vprintf("\n\n");
  /* nag_check_deriv_1 (c05zcc).
   * Derivative checker for (), thread-safe
   */
  nag_check_deriv_1(n, x, fvec, fjac, tdfjac, f, &comm, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_check_deriv_1 (c05zcc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  Vprintf("1st derivatives are consistent with residual values.\n\n");
  Vprintf("At the test point, f() gives\n\n");
  Vprintf("    Residuals            1st derivatives\n\n");
  for (i=0; i<n; ++i)
    {
      Vprintf("%13.3e", fvec[i]);
      for (j=0; j<n; ++j)
        Vprintf("%13.3e", FJAC(i,j));
      Vprintf("\n");
    }
 END:
  if (fjac) NAG_FREE(fjac);
  if (fvec) NAG_FREE(fvec);
  if (x) NAG_FREE(x);
  return exit_status;
}
static void f(Integer n, double x[], double fvec[], double fjac[],
              Integer tdfjac, Integer *userflag, Nag_User *comm)
{
  Integer j, k;

  if (*userflag != 2)
    {
      /* Calculate the function values */
      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
    {
      /* Calculate the corresponding first derivatives */
      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;
        }
    }
}