```/* nag_sparse_complex_gen_solve_ilu (f11dqc) Example Program.
*
* Copyright 2019 Numerical Algorithms Group.
*
* Mark 27.0, 2019.
*/
#include <nag.h>
int main(void)
{
/* Scalars */
Integer exit_status = 0;
double dtol, rnorm, tol;
Integer i, itn, la, lfill, m, maxitn, n, nnz, nnzc, npivm;
/* Arrays */
Complex *a = 0, *b = 0, *x = 0;
Integer *icol = 0, *idiag = 0, *ipivp = 0, *ipivq = 0, *irow = 0, *istr = 0;
char nag_enum_arg[40];
/* NAG types */
Nag_SparseNsym_Method method;
Nag_SparseNsym_Piv pstrat;
Nag_SparseNsym_Fact milu;
NagError fail;

INIT_FAIL(fail);

printf("nag_sparse_complex_gen_solve_ilu (f11dqc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &m);
scanf("%" NAG_IFMT "%*[^\n]", &nnz);
la = 2 * nnz;
if (!(a = NAG_ALLOC((la), Complex)) ||
!(b = NAG_ALLOC((n), Complex)) ||
!(x = NAG_ALLOC((n), Complex)) ||
!(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;
}
scanf("%39s%*[^\n]", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
method = (Nag_SparseNsym_Method) nag_enum_name_to_value(nag_enum_arg);
scanf("%" NAG_IFMT "%lf%*[^\n]", &lfill, &dtol);
scanf("%39s%*[^\n]", nag_enum_arg);
pstrat = (Nag_SparseNsym_Piv) nag_enum_name_to_value(nag_enum_arg);
scanf("%39s%*[^\n]", nag_enum_arg);
milu = (Nag_SparseNsym_Fact) nag_enum_name_to_value(nag_enum_arg);
scanf("%lf%" NAG_IFMT "%*[^\n]", &tol, &maxitn);
/* Read the matrix a */
for (i = 0; i < nnz; i++)
scanf(" ( %lf , %lf ) %" NAG_IFMT "%" NAG_IFMT "%*[^\n]",
&a[i].re, &a[i].im, &irow[i], &icol[i]);
/* Read rhs vector b and initial approximate solution x */
for (i = 0; i < n; i++)
scanf(" ( %lf , %lf )", &b[i].re, &b[i].im);
scanf("%*[^\n]");
for (i = 0; i < n; i++)
scanf(" ( %lf , %lf )", &x[i].re, &x[i].im);

/* Calculate incomplete LU factorization */
/* nag_sparse_complex_gen_precon_ilu (f11dnc)
* Complex sparse non-Hermitian linear systems, incomplete LU factorization
*/
nag_sparse_complex_gen_precon_ilu(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_complex_gen_precon_ilu (f11dnc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* solve ax = b */
/* nag_sparse_complex_gen_solve_ilu (f11dqc).
* Solution of complex sparse non-Hermitian linear system, RGMRES, CGS,
* Bi-CGSTAB or TFQMR method, preconditioner computed by
* nag_sparse_complex_gen_precon_ilu (f11dnc) (Black Box).
*/
nag_sparse_complex_gen_solve_ilu(method, n, nnz, a, la, irow, icol, ipivp, ipivq,
istr, idiag, b, m, tol, maxitn, x, &rnorm, &itn,
&fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sparse_complex_gen_solve_ilu (f11dqc).\n%s\n",
fail.message);
exit_status = 2;
goto END;
}
printf("Converged in%12" NAG_IFMT " iterations\n", itn);
printf("Final residual norm =%11.3e\n\n", rnorm);
/* Output x */
printf("%16s\n", "Solution");
for (i = 0; i < n; i++)
printf(" (%13.4e, %13.4e) \n", x[i].re, x[i].im);

END:
NAG_FREE(a);
NAG_FREE(b);
NAG_FREE(x);
NAG_FREE(icol);
NAG_FREE(idiag);
NAG_FREE(ipivp);
NAG_FREE(ipivq);
NAG_FREE(irow);
NAG_FREE(istr);
return exit_status;
}
```