```/* nag_zggev (f08wnc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.1, 2017.
*/

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <naga02.h>
#include <nagf08.h>
#include <nagm01.h>
#include <nagx02.h>
#include <nagx04.h>

#ifdef __cplusplus
extern "C"
{
#endif
static Integer NAG_CALL compare(const Nag_Pointer a, const Nag_Pointer b);
static Integer normalize_vectors(Integer n, Complex v[], Complex e[],
size_t rank[], const char *title);
static Integer sort_values (Integer n, Complex alpha[],
Complex beta[], Complex e[],
size_t rank[], double emod[]);
#ifdef __cplusplus
}
#endif

int main(void)
{
/* Scalars */
Integer           i, j, n, ninf, pda, pdb, pdvl, pdvr;
Integer           exit_status = 0;

/* Arrays */
Complex           *a = 0, *alpha = 0, *b = 0, *beta = 0, *vl = 0, *vr = 0;
Complex           *e = 0;
double            *emod = 0;
size_t            *rank = 0;
char              nag_enum_arg[40];

/* Nag Types */
NagError          fail;
Nag_OrderType     order;
Nag_LeftVecsType  jobvl;
Nag_RightVecsType jobvr;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J)  a[(J-1)*pda + I - 1]
#define B(I, J)  b[(J-1)*pdb + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J)  a[(I-1)*pda + J - 1]
#define B(I, J)  b[(I-1)*pdb + J - 1]
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_zggev (f08wnc) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%*[^\n]", &n);
if (n < 0) {
printf("Invalid n\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
*/
jobvl = (Nag_LeftVecsType) nag_enum_name_to_value(nag_enum_arg);
scanf(" %39s%*[^\n]", nag_enum_arg);
jobvr = (Nag_RightVecsType) nag_enum_name_to_value(nag_enum_arg);

pda = n;
pdb = n;
pdvl = (jobvl == Nag_LeftVecs ? n : 1);
pdvr = (jobvr == Nag_RightVecs ? n : 1);

/* Allocate memory */
if (!(a = NAG_ALLOC(n * n, Complex)) ||
!(alpha = NAG_ALLOC(n, Complex)) ||
!(b = NAG_ALLOC(n * n, Complex)) ||
!(beta = NAG_ALLOC(n, Complex)) ||
!(vl = NAG_ALLOC(pdvl * pdvl, Complex)) ||
!(e = NAG_ALLOC(n, Complex)) ||
!(emod = NAG_ALLOC(n, double)) ||
!(rank   = NAG_ALLOC(n, size_t)) ||
!(vr = NAG_ALLOC(pdvr * pdvr, Complex)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read in the matrices A and B */
for (i = 1; i <= n; ++i)
for (j = 1; j <= n; ++j)
scanf(" ( %lf , %lf )", &A(i, j).re, &A(i, j).im);
scanf("%*[^\n]");
for (i = 1; i <= n; ++i)
for (j = 1; j <= n; ++j)
scanf(" ( %lf , %lf )", &B(i, j).re, &B(i, j).im);
scanf("%*[^\n]");

/* Solve the generalized eigenvalue problem using nag_zggev (f08wnc). */
nag_zggev(order, jobvl, jobvr, n, a, pda, b, pdb, alpha, beta, vl, pdvl, vr,
pdvr, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_zggev (f08wnc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

printf("\n     Eigenvalues\n");
ninf = 0;
for (i = 0; i < n; ++i) {
if (beta[i].re == 0.0) {
ninf = ninf + 1;
printf(" %4" NAG_IFMT "     Infinite eigenvalue\n", i + 1);
}
}
if (ninf==0) {
/* Sort values by decreasing modulus and store in e[] */
exit_status=sort_values (n, alpha, beta, e, rank, emod);
for (i = 0; i < n; ++i) {
printf(" %4" NAG_IFMT "     (%7.3f,%7.3f)\n", i + 1, e[i].re, e[i].im);
}
if (jobvl == Nag_LeftVecs) {
exit_status = normalize_vectors(n, vl, e, rank,
"    Left eigenvectors (columns)");
}
if (jobvr == Nag_RightVecs && exit_status == 0) {
exit_status = normalize_vectors(n, vr, e, rank,
"   Right eigenvectors (columns)");
}
}

END:
NAG_FREE(a);
NAG_FREE(alpha);
NAG_FREE(b);
NAG_FREE(beta);
NAG_FREE(vl);
NAG_FREE(vr);
NAG_FREE(e);
NAG_FREE(emod);
NAG_FREE(rank);

return exit_status;
}
static Integer normalize_vectors(Integer n, Complex v[], Complex e[],
size_t rank[], const char *title)
{

Complex           scal;
double            r, rr;
Integer           errors = 0, i, j, k;
Nag_OrderType     order;
NagError          fail;

INIT_FAIL(fail);

#ifdef NAG_COLUMN_MAJOR
#define V(I, J)  v[(J-1)*n + I - 1]
order = Nag_ColMajor;
#else
#define V(I, J)  v[(I-1)*n + J - 1]
order = Nag_RowMajor;
#endif
/* Re-normalize the eigenvectors, largest absolute element real */
for (i=1; i<=n; i++) {
k = 0;
r = -1.0;
for (j=1; j<=n; j++) {
rr = nag_complex_abs(V(j,i));
if (rr>r) {
r = rr;
k = j;
}
}
scal.re = V(k,i).re/(r*r);
scal.im = -V(k,i).im/(r*r);
for (j=1; j<=n; j++) {
V(j,i) = nag_complex_multiply(V(j,i),scal);
}
V(k,i).re = 1.0;
V(k,i).im = 0.0;
}
/* Sort eigenvectors according to rank */
for (i=1; i<=n; i++) {
for (j=1; j<=n; j++)
e[j-1] = V(i,j);

/* Sort eigenvector row i using nag_reorder_vector (m01esc). */
nag_reorder_vector((Pointer) e, (size_t) n, sizeof(Complex),
(ptrdiff_t) sizeof(Complex), rank, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_reorder_vector (m01esc).\n%s\n", fail.message);
errors = 5;
goto END;
}
for (j=1; j<=n; j++)
V(i,j) = e[j-1];
}

printf("\n");
/* Print eigenvectors using nag_gen_complx_mat_print (x04dac). */
fflush(stdout);
nag_gen_complx_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
n, v, n, title, 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_gen_complx_mat_print (x04dac).\n%s\n",
fail.message);
errors = 6;
}
#undef V
END:
return errors;
}
static Integer sort_values (Integer n, Complex alpha[], Complex beta[],
Complex e[], size_t rank[], double emod[])
{
Integer       i, exit_status = 0;
NagError      fail;

INIT_FAIL(fail);

for (i = 0; i < n; ++i) {
/* nag_complex_divide (a02cdc): Quotient of two complex numbers;
* nag_complex_abs (a02ddc): Moduli of complex number.
*/
e[i] = nag_complex_divide(alpha[i], beta[i]);
emod[i] = nag_complex_abs(e[i]);
}
/* Rank sort eigenvalues by absolute values using
* nag_rank_sort (m01dsc).
*/
nag_rank_sort((Pointer) emod, (size_t) n, (ptrdiff_t) (sizeof(double)),
compare, Nag_Descending, rank, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_rank_sort (m01dsc).\n%s\n", fail.message);
exit_status = 10;
goto END;
}
/* Turn ranks into indices using nag_make_indices (m01zac). */
nag_make_indices(rank, (size_t) n, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_make_indices (m01zac).\n%s\n", fail.message);
exit_status = 11;
goto END;
}
/* Sort eigenvalues using nag_reorder_vector (m01esc). */
nag_reorder_vector((Pointer) e, (size_t) n, sizeof(Complex),
(ptrdiff_t) sizeof(Complex), rank, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_reorder_vector (m01esc).\n%s\n", fail.message);
exit_status = 12;
goto END;
}
END:
return exit_status;
}
static Integer NAG_CALL compare(const Nag_Pointer a, const Nag_Pointer b)
{
double x = *((const double *) a) - *((const double *) b);
return (x < 0.0 ? -1 : (x == 0.0 ? 0 : 1));
}
```