実対称行列の全ての固有値とオプションで全ての固有ベクトルを計算

nag_dsyevd (f08fcc) Example Program Data
  4                         :Value of n
  Nag_Lower                 :Value of uplo
  1.0
  2.0   2.0
  3.0   3.0   3.0
  4.0   4.0   4.0   4.0     :End of matrix A
  Nag_EigVecs               :Value of job

nag_dsyevd (f08fcc) Example Program Results

Eigenvalues
   -2.0531   -0.5146   -0.2943   12.8621
 Eigenvectors
            1          2          3          4
 1      1.0000     1.0000     1.0000     1.0000
 2      0.5129    -0.9431    -2.3976     1.0777
 3     -0.2240    -1.0537     2.3508     1.2393
 4     -0.8518     0.8831    -0.8879     1.4972

/* nag_dsyevd (f08fcc) Example Program.
 *
 * CLL6I261D/CLL6I261DL Version.
 *
 * Copyright 2017 Numerical Algorithms Group.
 *
 * Mark 26.1, 2017.
 */

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf08.h>
#include <nagx04.h>

int main(void)
{
  /* Scalars */
  Integer i, j, n, pda, w_len;
  Integer exit_status = 0;
  NagError fail;
  Nag_JobType job;
  Nag_UploType uplo;
  Nag_OrderType order;
  /* Arrays */
  char nag_enum_arg[40];
  double *a = 0, *w = 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);

  printf("nag_dsyevd (f08fcc) Example Program Results\n\n");

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

  /* Allocate memory */
  if (!(a = nAG_ALLOC(n * n, double)) || !(w = nAG_ALLOC(w_len, double)))
  {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }
  /* Read whether Upper or Lower part of A is stored */
  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);
  /* Read A from data file */
  if (uplo == Nag_Upper) {
    for (i = 1; i <= n; ++i) {
      for (j = i; j <= n; ++j)
        scanf("%lf", &A(i, j));
    }
    scanf("%*[^\n] ");
  }
  else {
    for (i = 1; i <= n; ++i) {
      for (j = 1; j <= i; ++j)
        scanf("%lf", &A(i, j));
    }
    scanf("%*[^\n] ");
  }
  /* Read type of job to be performed */
  scanf("%39s%*[^\n] ", nag_enum_arg);
  job = (Nag_JobType) nag_enum_name_to_value(nag_enum_arg);
  /* Calculate all the eigenvalues and eigenvectors of A */
  /* nag_dsyevd (f08fcc).
   * All eigenvalues and optionally all eigenvectors of real
   * symmetric matrix (divide-and-conquer)
   */
  nag_dsyevd(order, job, uplo, n, a, pda, w, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_dsyevd (f08fcc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Normalize the eigenvectors */
  for (j = 1; j <= n; j++) {
    for (i = n; i >= 1; i--) {
      A(i, j) = A(i, j) / A(1, j);
    }
  }
  /* Print eigenvalues and eigenvectors */
  printf("Eigenvalues\n");
  for (i = 0; i < n; ++i)
    printf("  %8.4f", w[i]);
  printf("\n");
  /* nag_gen_real_mat_print (x04cac).
   * Print real general matrix (easy-to-use)
   */
  fflush(stdout);
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n, a,
                         pda, "Eigenvectors", 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
END:
  nAG_FREE(a);
  nAG_FREE(w);
  return exit_status;
}