/* nag_lapacklin_dsptri (f07pjc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.2, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, j, n;
  Integer exit_status = 0;
  NagError fail;
  Nag_UploType uplo;
  Nag_OrderType order;
  /* Arrays */
  Integer *ipiv = 0;
  char nag_enum_arg[40];
  double *ap = 0;

#ifdef NAG_COLUMN_MAJOR
#define A_UPPER(I, J) ap[J * (J - 1) / 2 + I - 1]
#define A_LOWER(I, J) ap[(2 * n - J) * (J - 1) / 2 + I - 1]
  order = Nag_ColMajor;
#else
#define A_LOWER(I, J) ap[I * (I - 1) / 2 + J - 1]
#define A_UPPER(I, J) ap[(2 * n - I) * (I - 1) / 2 + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_lapacklin_dsptri (f07pjc) Example Program Results\n\n");

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

  /* Allocate memory */
  if (!(ipiv = NAG_ALLOC(n, Integer)) ||
      !(ap = NAG_ALLOC(n * (n + 1) / 2, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* Read A from data file */
  scanf(" %39s%*[^\n] ", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);

  if (uplo == Nag_Upper) {
    for (i = 1; i <= n; ++i) {
      for (j = i; j <= n; ++j)
        scanf("%lf", &A_UPPER(i, j));
    }
    scanf("%*[^\n] ");
  } else {
    for (i = 1; i <= n; ++i) {
      for (j = 1; j <= i; ++j)
        scanf("%lf", &A_LOWER(i, j));
    }
    scanf("%*[^\n] ");
  }

  /* Factorize A */
  /* nag_lapacklin_dsptrf (f07pdc).
   * Bunch-Kaufman factorization of real symmetric indefinite
   * matrix, packed storage
   */
  nag_lapacklin_dsptrf(order, uplo, n, ap, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dsptrf (f07pdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Compute inverse of A */
  /* nag_lapacklin_dsptri (f07pjc).
   * Inverse of real symmetric indefinite matrix, matrix
   * already factorized by nag_lapacklin_dsptrf (f07pdc), packed storage
   */
  nag_lapacklin_dsptri(order, uplo, n, ap, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dsptri (f07pjc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Print inverse */
  /* nag_file_print_matrix_real_packed (x04ccc).
   * Print real packed triangular matrix (easy-to-use)
   */
  fflush(stdout);
  nag_file_print_matrix_real_packed(order, uplo, Nag_NonUnitDiag, n, ap,
                                    "Inverse", 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_file_print_matrix_real_packed (x04ccc).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
END:
  NAG_FREE(ipiv);
  NAG_FREE(ap);
  return exit_status;
}