/* nag_det_real_gen (f03bac) Example Program.
 *
 * Copyright 2021 Numerical Algorithms Group.
 *
 * Mark 27.2, 2021.
 */
#include <math.h>
#include <nag.h>

int main(void) {
  /* Scalars */
  Integer exit_status = 0;
  Integer i, id, j, n, pda;
  double d;
  /* Arrays */
  Integer *ipiv = 0;
  double *a = 0;
  /* NAG types */
  NagError fail;
  Nag_OrderType order;
  Nag_MatrixType matrix = Nag_GeneralMatrix;
  Nag_DiagType diag = Nag_NonUnitDiag;

  printf("nag_det_real_gen (f03bac) Example Program Results\n");
  fflush(stdout);

  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%*[^\n]", &n);
  pda = n;
  if (!(a = NAG_ALLOC(n * n, double)) || !(ipiv = NAG_ALLOC(n, Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* Define matrix element A_ij in terms of elements of array a[k] */
#ifdef NAG_COLUMN_MAJOR
  order = Nag_ColMajor;
#define A(I, J) a[(J - 1) * pda + (I - 1)]
#else
  order = Nag_RowMajor;
#define A(J, I) a[(J - 1) * pda + (I - 1)]
#endif
  for (i = 1; i <= n; i++)
    for (j = 1; j <= n; j++)
      scanf("%lf", &A(i, j));
  scanf("%*[^\n] ");

  INIT_FAIL(fail);
  /* nag_lapacklin_dgetrf (f07adc) - LU factorization of real m by n matrix */
  nag_lapacklin_dgetrf(order, n, n, a, pda, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* nag_file_print_matrix_real_gen (x04cac).
   * Print real general matrix (easy-to-use)
   */
  printf("\n");
  fflush(stdout);
  nag_file_print_matrix_real_gen(order, matrix, diag, n, n, a, pda,
                                 "Array A after factorization", NULL, &fail);
  if (fail.code != NE_NOERROR) {
    printf("%s\n", fail.message);
    exit_status = 2;
    goto END;
  }

  printf("\nPivots:\n   ");
  for (j = 0; j < n; j++)
    printf("%11" NAG_IFMT " ", ipiv[j]);
  printf("\n");

  /* nag_det_real_gen (f03bac).
   * LU factorization and determinant of real matrix
   */
  nag_det_real_gen(order, n, a, pda, ipiv, &d, &id, &fail);
  if (fail.code != NE_NOERROR) {
    printf("%s\n", fail.message);
    exit_status = 3;
    goto END;
  }

  printf("d = %12.5f  id = %12" NAG_IFMT "\n", d, id);
  printf("Value of determinant = %13.5e\n", d * pow((double)2.0, id));

END:
  NAG_FREE(a);
  NAG_FREE(ipiv);

  return exit_status;
}