void
_arb_poly_log1p_series(arb_ptr res, arb_srcptr f, slong flen, slong n, slong prec)
{
arb_t a;
flen = FLINT_MIN(flen, n);
arb_init(a);
arb_log1p(a, f, prec);
if (flen == 1)
{
_arb_vec_zero(res + 1, n - 1);
}
else if (n == 2)
{
arb_add_ui(res, f + 0, 1, prec);
arb_div(res + 1, f + 1, res + 0, prec);
}
else if (_arb_vec_is_zero(f + 1, flen - 2)) /* f = a + bx^d */
{
slong i, j, d = flen - 1;
arb_add_ui(res, f + 0, 1, prec);
for (i = 1, j = d; j < n; j += d, i++)
{
if (i == 1)
arb_div(res + j, f + d, res, prec);
else
arb_mul(res + j, res + j - d, res + d, prec);
_arb_vec_zero(res + j - d + 1, flen - 2);
}
_arb_vec_zero(res + j - d + 1, n - (j - d + 1));
for (i = 2, j = 2 * d; j < n; j += d, i++)
arb_div_si(res + j, res + j, i % 2 ? i : -i, prec);
}
else
{
arb_ptr f_diff, f_inv;
slong alloc;
alloc = n + flen;
f_inv = _arb_vec_init(alloc);
f_diff = f_inv + n;
arb_add_ui(f_diff, f, 1, prec);
_arb_vec_set(f_diff + 1, f + 1, flen - 1);
_arb_poly_inv_series(f_inv, f_diff, flen, n, prec);
_arb_poly_derivative(f_diff, f, flen, prec);
_arb_poly_mullow(res, f_inv, n - 1, f_diff, flen - 1, n - 1, prec);
_arb_poly_integral(res, res, n, prec);
_arb_vec_clear(f_inv, alloc);
}
arb_swap(res, a);
arb_clear(a);
}
void
_arb_poly_compose(arb_ptr res,
arb_srcptr poly1, slong len1,
arb_srcptr poly2, slong len2, slong prec)
{
if (len1 == 1)
{
arb_set_round(res, poly1, prec);
}
else if (len2 == 1)
{
_arb_poly_evaluate(res, poly1, len1, poly2, prec);
}
else if (_arb_vec_is_zero(poly2 + 1, len2 - 2))
{
_arb_poly_compose_axnc(res, poly1, len1, poly2, poly2 + len2 - 1, len2 - 1, prec);
}
else if (len1 <= 7)
{
_arb_poly_compose_horner(res, poly1, len1, poly2, len2, prec);
}
else
{
_arb_poly_compose_divconquer(res, poly1, len1, poly2, len2, prec);
}
}
void
_arb_poly_compose_series(arb_ptr res, arb_srcptr poly1, slong len1,
arb_srcptr poly2, slong len2, slong n, slong prec)
{
if (len2 == 1)
{
arb_set_round(res, poly1, prec);
_arb_vec_zero(res + 1, n - 1);
}
else if (_arb_vec_is_zero(poly2 + 1, len2 - 2)) /* poly2 is a monomial */
{
slong i, j;
arb_t t;
arb_init(t);
arb_set(t, poly2 + len2 - 1);
arb_set_round(res, poly1, prec);
for (i = 1, j = len2 - 1; i < len1 && j < n; i++, j += len2 - 1)
{
arb_mul(res + j, poly1 + i, t, prec);
if (i + 1 < len1 && j + len2 - 1 < n)
arb_mul(t, t, poly2 + len2 - 1, prec);
}
if (len2 != 2)
for (i = 1; i < n; i++)
if (i % (len2 - 1) != 0)
arb_zero(res + i);
arb_clear(t);
}
else if (len1 < 6 || n < 6)
{
_arb_poly_compose_series_horner(res, poly1, len1, poly2, len2, n, prec);
}
else
{
_arb_poly_compose_series_brent_kung(res, poly1, len1, poly2, len2, n, prec);
}
}
void
_arb_poly_sqrt_series(arb_ptr g,
arb_srcptr h, slong hlen, slong len, slong prec)
{
hlen = FLINT_MIN(hlen, len);
while (hlen > 0 && arb_is_zero(h + hlen - 1))
hlen--;
if (hlen <= 1)
{
arb_sqrt(g, h, prec);
_arb_vec_zero(g + 1, len - 1);
}
else if (len == 2)
{
arb_sqrt(g, h, prec);
arb_div(g + 1, h + 1, h, prec);
arb_mul(g + 1, g + 1, g, prec);
arb_mul_2exp_si(g + 1, g + 1, -1);
}
else if (_arb_vec_is_zero(h + 1, hlen - 2))
{
arb_t t;
arb_init(t);
arf_set_si_2exp_si(arb_midref(t), 1, -1);
_arb_poly_binomial_pow_arb_series(g, h, hlen, t, len, prec);
arb_clear(t);
}
else
{
arb_ptr t;
t = _arb_vec_init(len);
_arb_poly_rsqrt_series(t, h, hlen, len, prec);
_arb_poly_mullow(g, t, len, h, hlen, len, prec);
_arb_vec_clear(t, len);
}
}
void
_arb_poly_exp_series(arb_ptr f, arb_srcptr h, slong hlen, slong n, slong prec)
{
hlen = FLINT_MIN(hlen, n);
if (hlen == 1)
{
arb_exp(f, h, prec);
_arb_vec_zero(f + 1, n - 1);
}
else if (n == 2)
{
arb_exp(f, h, prec);
arb_mul(f + 1, f, h + 1, prec); /* safe since hlen >= 2 */
}
else if (_arb_vec_is_zero(h + 1, hlen - 2)) /* h = a + bx^d */
{
slong i, j, d = hlen - 1;
arb_t t;
arb_init(t);
arb_set(t, h + d);
arb_exp(f, h, prec);
for (i = 1, j = d; j < n; j += d, i++)
{
arb_mul(f + j, f + j - d, t, prec);
arb_div_ui(f + j, f + j, i, prec);
_arb_vec_zero(f + j - d + 1, hlen - 2);
}
_arb_vec_zero(f + j - d + 1, n - (j - d + 1));
arb_clear(t);
}
else if (hlen <= arb_poly_newton_exp_cutoff)
{
_arb_poly_exp_series_basecase(f, h, hlen, n, prec);
}
else
{
arb_ptr g, t;
arb_t u;
int fix;
g = _arb_vec_init((n + 1) / 2);
fix = (hlen < n || h == f || !arb_is_zero(h));
if (fix)
{
t = _arb_vec_init(n);
_arb_vec_set(t + 1, h + 1, hlen - 1);
}
else
t = (arb_ptr) h;
arb_init(u);
arb_exp(u, h, prec);
_arb_poly_exp_series_newton(f, g, t, n, prec, 0, arb_poly_newton_exp_cutoff);
if (!arb_is_one(u))
_arb_vec_scalar_mul(f, f, n, u, prec);
_arb_vec_clear(g, (n + 1) / 2);
if (fix)
_arb_vec_clear(t, n);
arb_clear(u);
}
}
