NAG Library Manual, Mark 27.2
```/* nag_sparse_real_symm_sort (f11zbc) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.2, 2021.
*/

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

int main(void) {
double *a = 0;
Integer *icol = 0;
Integer *irow = 0, *istr = 0;
Integer exit_status = 0, i, n, nnz;
Nag_SparseSym_Zeros zero;
Nag_SparseSym_Dups dup;
NagError fail;

INIT_FAIL(fail);

printf("nag_sparse_real_symm_sort (f11zbc) Example Program Results\n");

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

/* Read order of matrix and number of nonzero entries */
scanf("%" NAG_IFMT "%*[^\n]", &n);
scanf("%" NAG_IFMT "%*[^\n]", &nnz);

/* Allocate memory */
istr = NAG_ALLOC(n + 1, Integer);
a = NAG_ALLOC(nnz, double);
irow = NAG_ALLOC(nnz, Integer);
icol = NAG_ALLOC(nnz, Integer);

if (!istr || !irow || !icol || !a) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read and output the original nonzero elements */
for (i = 1; i <= nnz; ++i)
scanf("%lf%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &a[i - 1], &irow[i - 1],
&icol[i - 1]);
printf(" Original elements \n");
printf(" nnz =  %6" NAG_IFMT "\n", nnz);
for (i = 1; i <= nnz; ++i)
printf(" %8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, a[i - 1],
irow[i - 1], icol[i - 1]);

/* Reorder, sum duplicates and remove zeros */
dup = Nag_SparseSym_SumDups;
zero = Nag_SparseSym_RemoveZeros;

/* nag_sparse_real_symm_sort (f11zbc).
* Sparse sort (symmetric)
*/
nag_sparse_real_symm_sort(n, &nnz, a, irow, icol, dup, zero, istr, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_real_symm_sort (f11zbc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* Output results */
printf(" Reordered elements \n");
printf(" nnz = %4" NAG_IFMT "\n", nnz);

for (i = 1; i <= nnz; ++i)
printf(" %8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, a[i - 1],
irow[i - 1], icol[i - 1]);

END:
NAG_FREE(istr);
NAG_FREE(irow);
NAG_FREE(icol);
NAG_FREE(a);
return exit_status;
}
```