NAG Library Manual, Mark 28.5
```/* nag_sparse_real_gen_sort (f11zac) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.5, 2022.
*/

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

int main(void) {
double *b = 0, *c = 0, *a = 0, anorm = 0.0;
Integer *bcol = 0, *ccol = 0, *icol = 0, *icol2 = 0, *trcol = 0;
Integer *brow = 0, *crow = 0, *irow = 0, *istr = 0, *trrow = 0;
Integer exit_status = 0, i, j, n, bnnz, cnnz, nnz;
Nag_SparseNsym_Zeros zero;
Nag_SparseNsym_Dups dup;
Nag_NormType norm;
NagError fail;

INIT_FAIL(fail);

printf("nag_sparse_real_gen_sort (f11zac) Example Program Results\n\n");

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

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

/* Allocate memory */
b = NAG_ALLOC(bnnz, double);
brow = NAG_ALLOC(bnnz, Integer);
bcol = NAG_ALLOC(bnnz, Integer);

if (!b || !brow || !bcol) {
printf("Allocation failure for b\n");
exit_status = -1;
goto END;
}

/* Read the nonzero elements of B */
for (i = 0; i < bnnz; ++i)
scanf("%lf%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &b[i], &brow[i], &bcol[i]);

/* Read number of nonzero entries of C */
scanf("%" NAG_IFMT "%*[^\n]", &cnnz);

/* Allocate memory */
c = NAG_ALLOC(cnnz, double);
crow = NAG_ALLOC(cnnz, Integer);
ccol = NAG_ALLOC(cnnz, Integer);

if (!c || !crow || !ccol) {
printf("Allocation failure for c\n");
exit_status = -1;
goto END;
}

/* Read the nonzero elements of C */
for (i = 0; i < cnnz; ++i)
scanf("%lf%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &c[i], &crow[i], &ccol[i]);

/* Output the original non-zero elements */
printf("Elements of B\n");
printf("nnz =  %4" NAG_IFMT "\n", bnnz);
printf("%8s%16s%8s%8s\n", "", "b", "brow", "bcol");
for (i = 0; i < bnnz; ++i)
printf("%8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, b[i],
brow[i], bcol[i]);

printf("Elements of C\n");
printf("nnz =  %4" NAG_IFMT "\n", cnnz);
printf("%8s%16s%8s%8s\n", "", "c", "crow", "ccol");
for (i = 0; i < cnnz; ++i)
printf("%8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, c[i],
crow[i], ccol[i]);

/* Set initial size for resulting array a, and allocate ememory */
nnz = bnnz + cnnz;

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

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

/*  Concatenate sparse matrices B and C to form A */
for (i = 0; i < bnnz; ++i) {
a[i] = b[i];
irow[i] = brow[i];
icol[i] = bcol[i];
}
for (i = 0; i < cnnz; ++i) {
a[bnnz + i] = c[i];
irow[bnnz + i] = crow[i];
icol[bnnz + i] = ccol[i];
}

/* Reorder along rows, sum duplicates and remove zeros */

dup = Nag_SparseNsym_SumDups;
zero = Nag_SparseNsym_RemoveZeros;

/* nag_sparse_real_gen_sort (f11zac).
* Sparse sort (nonsymmetric)
*/
nag_sparse_real_gen_sort(n, &nnz, a, irow, icol, dup, zero, istr, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_real_gen_sort (f11zac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Output results */
printf("Summed and reordered elements of A = B + C, along rows first\n");
printf("nnz = %4" NAG_IFMT "\n", nnz);
printf("%8s%16s%8s%8s\n", "", "a", "irow", "icol");

for (i = 0; i < nnz; ++i)
printf("%8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, a[i],
irow[i], icol[i]);

/* Reorder down columns, fail on duplicates or zeros.
* Creates CCS storage format as side-effect
*/
dup = Nag_SparseNsym_FailDups;
zero = Nag_SparseNsym_FailZeros;
INIT_FAIL(fail);

/* nag_sparse_real_gen_sort (f11zac).
* Sparse sort (nonsymmetric)
*/
nag_sparse_real_gen_sort(n, &nnz, a, icol, irow, dup, zero, istr, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_real_gen_sort (f11zac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Output results */
printf("Reordered elements, along columns first\n");
printf("nnz = %4" NAG_IFMT "\n", nnz);
printf("%8s%16s%8s%8s\n", "", "a", "irow", "icol");

for (i = 0; i < nnz; ++i)
printf("%8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, a[i],
irow[i], icol[i]);

/* Output results */
printf("Same matrix in CCS format\n");
printf("nnz = %4" NAG_IFMT "\n", nnz);
printf("%8s%16s%8s%8s\n", "", "a", "irowix", "icolzp");

for (i = 0; i < nnz; ++i) {
if (i < n + 1) {
printf("%8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, a[i],
irow[i], istr[i]);
} else {
printf("%8" NAG_IFMT "%16.4e%8" NAG_IFMT "\n", i, a[i], irow[i]);
}
}

/* Calculate 1-norm from Compressed Column Storage format */
norm = Nag_RealOneNorm;
INIT_FAIL(fail);

/* nag_sparse_direct_real_gen_norm (f11mlc).
* 1-norm, infinity-norm, largest absolute element, real
* general matrix
*/
nag_sparse_direct_real_gen_norm(norm, &anorm, n, istr, irow, a, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_direct_real_gen_norm (f11mlc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
/* Output norm */
printf("%s %16.4e\n", "One-norm", anorm);

/* Convert CCS format back to Coordinate Storage */
icol2 = NAG_ALLOC(nnz, Integer);

for (i = 0; i < n; ++i)
for (j = istr[i] - 1; j < istr[i + 1] - 1; ++j)
icol2[j] = i + 1;

/* Check that result matches original Coordinate Storage Data */
for (i = 0; i < nnz; ++i)
if (icol[i] != icol2[i]) {
printf("Converted CCS format back to CS format, result differs "
"from original!\n");
goto END;
}
printf("Converted CCS format back to CS format, result matches original\n");

/* Swap the row and column vectors to obtain transpose of A */
trrow = icol;
trcol = irow;

/* Output transposed results */
printf("Transpose of summed and reordered elements, along rows first\n");
printf("nnz = %4" NAG_IFMT "\n", nnz);
printf("%8s%16s%8s%8s\n", "", "a", "irow", "icol");

for (i = 0; i < nnz; ++i)
printf("%8" NAG_IFMT "%16.4e%8" NAG_IFMT "%8" NAG_IFMT "\n", i, a[i],
trrow[i], trcol[i]);

END:
NAG_FREE(istr);
NAG_FREE(brow);
NAG_FREE(c);
NAG_FREE(crow);
NAG_FREE(irow);
NAG_FREE(bcol);
NAG_FREE(ccol);
NAG_FREE(icol);
NAG_FREE(a);
NAG_FREE(icol2);
NAG_FREE(b);

return exit_status;
}
```