/* nag_fit_glin_linf (e02gcc) Example Program.
 *
 * Copyright 2021 Numerical Algorithms Group.
 *
 * Mark 27.3, 2021.
 */

#include <math.h>
#include <nag.h>
#include <stdio.h>

int main(void) {
  /* Scalars */
  double relerr, resmax, t, tol;
  Integer exit_status, i, irank, iter, m, n, pda;
  NagError fail;
  Nag_OrderType order;

  /* Arrays */
  double *a = 0, *b = 0, *x = 0;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
  order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  exit_status = 0;
  printf("nag_fit_glin_linf (e02gcc) Example Program Results\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");

  n = 3;
  scanf("%" NAG_IFMT "%*[^\n] ", &m);
  if (m > 0) {
    /* Allocate memory */
    if (!(a = NAG_ALLOC((n + 3) * (m + 1), double)) ||
        !(b = NAG_ALLOC(m, double)) || !(x = NAG_ALLOC(n, double))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

    if (order == Nag_ColMajor)
      pda = n + 3;
    else
      pda = m + 1;

    for (i = 1; i <= m; ++i) {
      scanf("%lf%lf%*[^\n] ", &t, &b[i - 1]);
      A(1, i) = exp(t);
      A(2, i) = exp(-t);
      A(3, i) = 1.0;
    }
    tol = 0.0;
    relerr = 0.0;
    /* nag_fit_glin_linf (e02gcc).
     * L_infinity-approximation by general linear function
     */
    nag_fit_glin_linf(order, m, n, a, b, tol, &relerr, x, &resmax, &irank,
                      &iter, &fail);
    if (fail.code != NE_NOERROR) {
      printf("Error from nag_fit_glin_linf (e02gcc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    } else {
      printf("\n");
      printf("resmax = %11.2e  Rank = %5" NAG_IFMT "  Iterations ="
             " %5" NAG_IFMT "\n",
             resmax, irank, iter);

      printf("\n");
      printf("Solution\n");

      for (i = 1; i <= n; ++i)
        printf("%10.4f", x[i - 1]);
      printf("\n");
    }
  }
END:
  NAG_FREE(a);
  NAG_FREE(b);
  NAG_FREE(x);

  return exit_status;
}