```/* nag_sparse_nsym_precon_ilu_solve (f11dbc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.1, 2017.
*/
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf11.h>
int main(void)
{
/* Scalars */
Integer exit_status = 0;
double dtol;
Integer i, la, lfill, n, nnz, nnzc, npivm;
/* Arrays */
double *a = 0, *x = 0, *y = 0;
Integer *icol = 0, *idiag = 0, *ipivp = 0, *ipivq = 0, *irow = 0, *istr = 0;
/* NAG types */
Nag_SparseNsym_Piv pstrat;
Nag_SparseNsym_Fact milu;
Nag_SparseNsym_CheckData check;
Nag_TransType trans;
NagError fail;

INIT_FAIL(fail);

printf("nag_sparse_nsym_precon_ilu_solve (f11dbc) Example Program Results");
printf("\n\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%*[^\n]", &n);
scanf("%" NAG_IFMT "%*[^\n]", &nnz);
la = 2 * nnz;
if (!(a = NAG_ALLOC((la), double)) ||
!(x = NAG_ALLOC((n), double)) ||
!(y = NAG_ALLOC((n), double)) ||
!(icol = NAG_ALLOC((la), Integer)) ||
!(idiag = NAG_ALLOC((n), Integer)) ||
!(ipivp = NAG_ALLOC((n), Integer)) ||
!(ipivq = NAG_ALLOC((n), Integer)) ||
!(irow = NAG_ALLOC((la), Integer)) ||
!(istr = NAG_ALLOC((n + 1), Integer))
)
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* Read the nonzero elements of the matrix a */
for (i = 0; i < nnz; i++)
scanf("%lf%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &a[i], &irow[i], &icol[i]);
/* Read the vector y */
for (i = 0; i < n; i++)
scanf("%lf", &y[i]);

/* Calculate LU factorization */
lfill = -1;
dtol = 0.0;
pstrat = Nag_SparseNsym_CompletePiv;
milu = Nag_SparseNsym_UnModFact;
/* nag_sparse_nsym_fac (f11dac).
* Incomplete LU factorization (nonsymmetric)
*/
nag_sparse_nsym_fac(n, nnz, &a, &la, &irow, &icol, lfill, dtol, pstrat,
milu, ipivp, ipivq, istr, idiag, &nnzc, &npivm, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_nsym_fac (f11dac)\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Check value of npivm */
if (npivm > 0) {
printf("Factorization is not complete \n");
goto END;
}
/* Solve P L D U x = y */
check = Nag_SparseNsym_Check;
trans = Nag_NoTrans;
/* nag_sparse_nsym_precon_ilu_solve (f11dbc)
* Solution of linear system involving incomplete LU preconditioning matrix
*/
nag_sparse_nsym_precon_ilu_solve(trans, n, a, la, irow, icol, ipivp, ipivq,
istr, idiag, check, y, x, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_nsym_precon_ilu_solve (f11dbc)\n%s\n",
fail.message);
exit_status = 2;
goto END;
}
/* Output results */
printf(" Solution of linear system \n");
for (i = 0; i < n; i++)
printf("%16.4e\n", x[i]);
END:
NAG_FREE(a);
NAG_FREE(x);
NAG_FREE(y);
NAG_FREE(icol);
NAG_FREE(idiag);
NAG_FREE(ipivp);
NAG_FREE(ipivq);
NAG_FREE(irow);
NAG_FREE(istr);
return exit_status;
}
```