/* nag_fit_glin_l1sol (e02gac) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.1, 2024.
 */

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

int main(void) {
  /* Scalars */
  double resid, t, tol;
  Integer exit_status, i, iter, m, rank, n, nplus2, 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_l1sol (e02gac) Example Program Results\n");

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

  n = 3;
  nplus2 = n + 2;
  scanf("%" NAG_IFMT "%*[^\n] ", &m);
  if (m > 0) {
    /* Allocate memory */
    if (!(a = NAG_ALLOC((m + 2) * nplus2, double)) ||
        !(b = NAG_ALLOC(m, double)) || !(x = NAG_ALLOC(nplus2, double))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

    if (order == Nag_ColMajor)
      pda = m + 2;
    else
      pda = nplus2;

    for (i = 1; i <= m; ++i) {
      scanf("%lf%lf%*[^\n] ", &t, &b[i - 1]);
      A(i, 1) = exp(t);
      A(i, 2) = exp(-t);
      A(i, 3) = 1.0;
    }
    tol = 0.0;
    /* nag_fit_glin_l1sol (e02gac).
     * L_1-approximation by general linear function
     */
    nag_fit_glin_l1sol(order, m, a, b, nplus2, tol, x, &resid, &rank, &iter,
                       &fail);
    if (fail.code == NE_INT || fail.code == NE_INT_2 ||
        fail.code == NE_TOO_MANY_ITER || fail.code == NE_NO_LICENCE) {
      printf("Error from nag_fit_glin_l1sol (e02gac).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    } else {
      printf("\n");
      printf("resid = %11.2e  Rank = %5" NAG_IFMT "  Iterations ="
             " %5" NAG_IFMT "\n",
             resid, rank, 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;
}