NAG Library Manual, Mark 28.5
/* nag_blast_daxpby (f16ecc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.5, 2022.
*/

#include <nag.h>
#include <stdio.h>
int main(void) {
/* Scalars */
Integer exit_status, i, incx, incy, ix, iy, n;
double alpha, beta;
/* Arrays */
double *x = 0, *y = 0;
/* Nag Types */
NagError fail;

exit_status = 0;
INIT_FAIL(fail);

printf("nag_blast_daxpby (f16ecc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
/* Read number of elements */
scanf("%" NAG_IFMT "%*[^\n] ", &n);
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &incx, &incy);
/* Read factors alpha and beta */
scanf("%lf%lf%*[^\n] ", &alpha, &beta);

if (n > 0) {
/* Allocate memory */
if (!(x = NAG_ALLOC(MAX(1, 1 + (n - 1) * ABS(incx)), double)) ||
!(y = NAG_ALLOC(MAX(1, 1 + (n - 1) * ABS(incy)), double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
} else {
printf("Invalid n\n");
exit_status = 1;
goto END;
}

/* Read the vectors x and y and store forwards or backwards
* as determined by incx (resp. incy). */
for (i = 0, ix = (incx > 0 ? 0 : (1 - n) * incx); i < n; i++, ix += incx)
scanf("%lf", &x[ix]);
scanf("%*[^\n] ");

for (i = 0, iy = (incy > 0 ? 0 : (1 - n) * incy); i < n; i++, iy += incy)
scanf("%lf", &y[iy]);
scanf("%*[^\n] ");

/* nag_blast_daxpby (f16ecc).
* Performs y := alpha*x + beta*y  */
nag_blast_daxpby(n, alpha, x, incx, beta, y, incy, &fail);

if (fail.code != NE_NOERROR) {
printf("Error from nag_blast_daxpby (f16ecc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Display the vector y forwards or backwards
* as determined by incy. */
printf("Result of the scaled vector accumulation is\n");
printf("y = (");
for (i = 0, iy = (incy > 0 ? 0 : (1 - n) * incy); i < n; i++, iy += incy)
printf("%9.4f%s", y[iy], (i < n - 1 ? ", " : ")\n"));

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

return exit_status;
}