void
fmpz_poly_compose_divconquer(fmpz_poly_t res,
const fmpz_poly_t poly1, const fmpz_poly_t poly2)
{
const long len1 = poly1->length;
const long len2 = poly2->length;
long lenr;
if (len1 == 0)
{
fmpz_poly_zero(res);
return;
}
if (len1 == 1 || len2 == 0)
{
fmpz_poly_set_fmpz(res, poly1->coeffs);
return;
}
lenr = (len1 - 1) * (len2 - 1) + 1;
if (res != poly1 && res != poly2)
{
fmpz_poly_fit_length(res, lenr);
_fmpz_poly_compose_divconquer(res->coeffs, poly1->coeffs, len1,
poly2->coeffs, len2);
_fmpz_poly_set_length(res, lenr);
_fmpz_poly_normalise(res);
}
else
{
fmpz_poly_t t;
fmpz_poly_init2(t, lenr);
_fmpz_poly_compose_divconquer(t->coeffs, poly1->coeffs, len1,
poly2->coeffs, len2);
_fmpz_poly_set_length(t, lenr);
_fmpz_poly_normalise(t);
fmpz_poly_swap(res, t);
fmpz_poly_clear(t);
}
}
void
_fmpz_poly_compose(fmpz * res, const fmpz * poly1, slong len1,
const fmpz * poly2, slong len2)
{
if (len1 == 1)
fmpz_set(res, poly1);
else if (len2 == 1)
_fmpz_poly_evaluate_fmpz(res, poly1, len1, poly2);
else if (len1 <= 4)
_fmpz_poly_compose_horner(res, poly1, len1, poly2, len2);
else
_fmpz_poly_compose_divconquer(res, poly1, len1, poly2, len2);
}