```/* nag_dsyevd (f08fcc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.2, 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("%" NAG_IFMT "%*[^\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;
}
```