NAG Library Manual, Mark 27.2
```/* nag_lapackeig_zggglm (f08zpc) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.2, 2021.
*/

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

int main(void) {
/* Scalars */
double rnorm;
Integer i, j, m, n, p, pda, pdb;
Integer exit_status = 0;
NagError fail;
Nag_OrderType order;
/* Arrays */
Complex *a = 0, *b = 0, *d = 0, *x = 0, *y = 0;

#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_lapackeig_zggglm (f08zpc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n, &m, &p);

#ifdef NAG_COLUMN_MAJOR
pda = n;
pdb = n;
#else
pda = m;
pdb = p;
#endif

/* Allocate memory */
if (!(a = NAG_ALLOC(n * m, Complex)) || !(b = NAG_ALLOC(n * p, Complex)) ||
!(d = NAG_ALLOC(n, Complex)) || !(x = NAG_ALLOC(m, Complex)) ||
!(y = NAG_ALLOC(p, Complex))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read A, B and D from data file */
for (i = 1; i <= n; ++i) {
for (j = 1; j <= m; ++j)
scanf(" ( %lf , %lf )", &A(i, j).re, &A(i, j).im);
}
scanf("%*[^\n] ");

for (i = 1; i <= n; ++i) {
for (j = 1; j <= p; ++j)
scanf(" ( %lf , %lf )", &B(i, j).re, &B(i, j).im);
}
scanf("%*[^\n] ");

for (i = 1; i <= n; ++i)
scanf(" ( %lf , %lf )", &d[i - 1].re, &d[i - 1].im);
scanf("%*[^\n] ");

/* Solve the weighted least squares problem      */
/* minimize ||inv(B)*(d - A*x)|| (in the 2-norm) */
nag_lapackeig_zggglm(order, n, m, p, a, pda, b, pdb, d, x, y, &fail);

if (fail.code == NE_NOERROR) {
/* Print least squares solution */
printf("Weighted least squares solution\n");
for (i = 1; i <= m; ++i)
printf("(%9.4f, %9.4f)%s", x[i - 1].re, x[i - 1].im,
i % 3 == 0 || i == m ? "\n" : " ");

/* Print residual vector y = inv(B)*(d - A*x) */
printf("\nResidual vector\n");
for (i = 1; i <= p; ++i)
printf("(%11.2e, %11.2e)%s", y[i - 1].re, y[i - 1].im,
i % 3 == 0 || i == p ? "\n" : " ");

/* Compute and print the square root of the residual sum of */
/* squares                                                  */
nag_blast_zge_norm(Nag_ColMajor, Nag_FrobeniusNorm, 1, p, y, 1, &rnorm,
&fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_blast_zge_norm (f16uac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

printf("\nSquare root of the residual sum of squares\n");
printf("%11.2e\n", rnorm);
} else {
printf("Error from nag_lapackeig_zggglm (f08zpc).\n%s\n", fail.message);
exit_status = 1;
}

END:
NAG_FREE(a);
NAG_FREE(b);
NAG_FREE(d);
NAG_FREE(x);
NAG_FREE(y);

return exit_status;
}
```