/* nag_lapackeig_dbdsqr (f08mec) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.3, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, n, pdvt, pdu;
  Integer exit_status = 0, ncc = 0, ldc = 1;
  double zero = 0.0, one = 1.0;
  /* Arrays */
  char nag_enum_arg[40];
  double c[1];
  double *d = 0, *e = 0, *u = 0, *vt = 0;

  /* Nag Types */
  NagError fail;
  Nag_UploType uplo;
  Nag_OrderType order;

  INIT_FAIL(fail);

  printf("nag_lapackeig_dbdsqr (f08mec) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "%*[^\n]", &n);
  if (n < 0) {
    printf("Invalid n\n");
    exit_status = 1;
    goto END;
  }

#ifdef NAG_COLUMN_MAJOR
  order = Nag_ColMajor;
#else
  order = Nag_RowMajor;
#endif
  pdu = n;
  pdvt = n;

  /* Allocate memory */
  if (!(d = NAG_ALLOC(n, double)) || !(e = NAG_ALLOC(n - 1, double)) ||
      !(u = NAG_ALLOC(n * n, double)) || !(vt = NAG_ALLOC(n * n, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* Read B from data file */
  for (i = 0; i < n; ++i)
    scanf("%lf", &d[i]);
  scanf("%*[^\n]");
  for (i = 0; i < n - 1; ++i)
    scanf("%lf", &e[i]);
  scanf("%*[^\n]");
  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);

  /* Initialize U and VT to be the unit matrix to obtain SVD of input
   * bidiagonal matrix nag_blast_dge_load (f16qhc).
   * General matrix initialization.
   */
  nag_blast_dge_load(order, n, n, zero, one, u, pdu, &fail);
  nag_blast_dge_load(order, n, n, zero, one, vt, pdvt, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_blast_dge_load (f16qhc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* nag_lapackeig_dbdsqr (f08mec).
   * SVD of real bidiagonal matrix reduced from real general
   * matrix.
   */
  nag_lapackeig_dbdsqr(order, uplo, n, n, n, ncc, d, e, vt, pdvt, u, pdu, c,
                       ldc, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapackeig_dbdsqr (f08mec).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Print singular values, left & right singular vectors */
  printf("\nSingular values\n   ");
  for (i = 0; i < n; ++i)
    printf(" %7.4f%s", d[i], i % 8 == 7 ? "\n" : "");
  printf("\n\n");

  /* nag_file_print_matrix_real_gen (x04cac).
   * Print real general matrix (easy-to-use)
   */
  fflush(stdout);
  nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                                 n, vt, pdvt, "Right singular vectors, by row",
                                 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
  printf("\n");
  /* nag_file_print_matrix_real_gen (x04cac), see above. */
  fflush(stdout);
  nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                                 n, u, pdu, "Left singular vectors, by column",
                                 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
END:
  NAG_FREE(d);
  NAG_FREE(e);
  NAG_FREE(u);
  NAG_FREE(vt);

  return exit_status;
}