NAG Library Manual, Mark 27.2
```/* nag_blast_zgemv (f16sac) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.2, 2021.
*/

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

int main(void) {

/* Scalars */
Complex alpha, beta;
Integer exit_status, i, incx, incy, j, m, n, pda, xlen, ylen;

/* Arrays */
Complex *a = 0, *x = 0, *y = 0;
char nag_enum_arg[40];

/* Nag Types */
NagError fail;
Nag_OrderType order;
Nag_TransType trans;

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

exit_status = 0;
INIT_FAIL(fail);

printf("nag_blast_zgemv (f16sac) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");

/* Read the problem dimensions */
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &m, &n);

/* Read the transpose parameter */
scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
trans = (Nag_TransType)nag_enum_name_to_value(nag_enum_arg);
scanf(" ( %lf , %lf ) ( %lf , %lf )%*[^\n] ", &alpha.re, &alpha.im, &beta.re,
&beta.im);
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &incx, &incy);

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

if (trans == Nag_NoTrans) {
xlen = MAX(1, 1 + (n - 1) * ABS(incx));
ylen = MAX(1, 1 + (m - 1) * ABS(incy));
} else {
xlen = MAX(1, 1 + (m - 1) * ABS(incx));
ylen = MAX(1, 1 + (n - 1) * ABS(incy));
}

if (m > 0 && n > 0) {
/* Allocate memory */
if (!(a = NAG_ALLOC(m * n, Complex)) || !(x = NAG_ALLOC(xlen, Complex)) ||
!(y = NAG_ALLOC(ylen, Complex))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
} else {
printf("Invalid m or n\n");
exit_status = 1;
return exit_status;
}

/* Input matrix A and vectors x and y */

for (i = 1; i <= m; ++i) {
for (j = 1; j <= n; ++j)
scanf(" ( %lf , %lf )", &A(i, j).re, &A(i, j).im);
scanf("%*[^\n] ");
}
for (i = 1; i <= xlen; ++i)
scanf(" ( %lf , %lf )%*[^\n] ", &x[i - 1].re, &x[i - 1].im);
for (i = 1; i <= ylen; ++i)
scanf(" ( %lf , %lf )%*[^\n] ", &y[i - 1].re, &y[i - 1].im);

/* nag_blast_zgemv (f16sac).
* Complex valued matrix-vector multiply.
*
*/
nag_blast_zgemv(order, trans, m, n, alpha, a, pda, x, incx, beta, y, incy,
&fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_blast_zgemv.\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print output vector y */
printf("%s\n", "  y");
for (i = 1; i <= ylen; ++i) {
printf("(%11f,%11f)\n", y[i - 1].re, y[i - 1].im);
}

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

return exit_status;
}
```