```/* nag_sparse_sym_rcm (f11yec) Example Program.
*
* Copyright 2014 Numerical Algorithms Group.
*
* Mark 25, 2014.
*/
#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf11.h>

void plot(const Integer n, const Integer nnz, Integer *perm,
Integer *icolzp, Integer *irowix);
void uncompress(Integer n, Integer *icolzp, Integer *icol);

int main(void)
{
/* Scalars */
Integer n, nnz, exit_status = 0, doplot = 0, i;
/* Arrays */
Integer info[4];
Nag_Boolean lopts[5];
/* Nag Types */
NagError fail;

INIT_FAIL(fail);
printf("nag_sparse_sym_rcm (f11yec) Example Program Results\n");
/* Skip heading in data file and
* read Size of the matrix and Number of non-zero elements
*/
scanf("%*[^\n] ");
scanf("%ld%*[^\n] ", &n);
scanf("%ld%*[^\n] ", &nnz);
if ( !(icolzp = NAG_ALLOC((n+1), Integer)) ||
!(irowix = NAG_ALLOC((nnz), Integer)) ||
!(perm = NAG_ALLOC((n), Integer))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
for (i = 0; i < nnz; i+=1) scanf("%ld", &irowix[i]);
scanf("%*[^\n] ");
for (i = 0; i < (n + 1); i+=1) scanf("%ld", &icolzp[i]);
scanf("%*[^\n] ");
/* Set options */
lopts[0 /* Use Mask                 */] = Nag_FALSE;
lopts[1 /* Don't reverse            */] = Nag_FALSE;
lopts[2 /* Check symmetry           */] = Nag_TRUE;
lopts[3 /* Compute bandwidth before */] = Nag_TRUE;
lopts[4 /* Compute bandwidth after  */] = Nag_TRUE;
/* nag_sparse_sym_rcm (f11yec).
* Reverse Cuthill-McKee reordering of a real sparse symmetric
* matrix in CCS format
*/
nag_sparse_sym_rcm(n, nnz, icolzp, irowix, lopts, mask, perm, info, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_sym_rcm (f11yec).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
/* Print results */
printf("Permutation (perm):\n");
for (i = 0; i < n; i+=1) {
printf("    %3ld", perm[i]);
if (i%6==5) printf("\n");
}
printf("\n\nStatistics:\n");
printf(" %s%6ld\n"," Before:  Bandwidth = ", info[0]);
printf(" %s%6ld\n"," Before:  Profile   = ", info[1]);
printf(" %s%6ld\n"," After :  Bandwidth = ", info[2]);
printf(" %s%6ld\n"," After :  Profile   = ", info[3]);
/* Print matrix entries and permuted entries in form suitable
* for plotting
*/
if (doplot) plot(n, nnz, perm, icolzp, irowix);
END:
NAG_FREE(icolzp);
NAG_FREE(irowix);
NAG_FREE(perm);

return exit_status;
}

void uncompress(Integer n, Integer *icolzp, Integer *icol)
{
Integer i, j, col_beg, col_end;
for (i=0; i< n; i++) {
col_end = icolzp[i+1] - 1;
col_beg = icolzp[i];
for (j = col_beg; j <= col_end; j++) icol[j-1] = i+1;
}

}
void plot(Integer n, Integer nnz, Integer *perm, Integer *icolzp,
Integer *irowix)
{
/* Put data, suitable for plotting matrix structure, in data file */

/* Scalars */
Integer i, nnz2;
/* Arrays */
double  *a=0;
Integer *icolix=0, *ipcolix=0, *iperm=0, *iprowix=0, *istr=0;
/* Nag Types */
NagError fail;

INIT_FAIL(fail);
if ( !(icolix = NAG_ALLOC(nnz, Integer)) ||
!(ipcolix = NAG_ALLOC(nnz, Integer)) ||
!(iprowix = NAG_ALLOC(nnz, Integer)) ||
!(iperm = NAG_ALLOC(n, Integer)) ||
!(a = NAG_ALLOC(nnz, double)) ||
!(istr = NAG_ALLOC(n+1, Integer))) {
printf("Allocation failure\n");
return;
}
/* Decompress icolzp to full set of column indices (icolix)
* and compute inverse permutation
*/
uncompress(n, icolzp, icolix);
for (i=0; i< n; i++) {
iperm[perm[i]-1] = i+1;
}
/* Original matrix structure */
for (i=0; i< nnz; i++) {
a[i] = icolix[i]*.01 + 1.0 * irowix[i];
printf("%8ld    ", irowix[i]);
printf("%8ld    ", icolix[i]);
printf("%8.2f\n", a[i]);
}
printf("\n");
/* Apply Inverse Permutation */
for (i=0; i< nnz; i++) {
ipcolix[i] = iperm[icolix[i]-1];
iprowix[i] = iperm[irowix[i]-1];
}
/* Reorder (in exit: istr contains new CCS icolzp) */
nnz2 =  nnz;
nag_sparse_nsym_sort(n, &nnz2, a, ipcolix, iprowix, Nag_SparseNsym_FailDups,
Nag_SparseNsym_KeepZeros, istr, &fail);
/* Permuted matrix structure */
for (i=0; i<nnz2; i++) {
printf("%8ld    ", iprowix[i]);
printf("%8ld    ", ipcolix[i]);
printf("%8.2f\n", a[i]);
}
NAG_FREE(icolix);
NAG_FREE(ipcolix);
NAG_FREE(iprowix);
NAG_FREE(iperm);
NAG_FREE(a);
NAG_FREE(istr);
}
```