arb/acb_dirichlet/hurwitz.c

50 lines
1.3 KiB
C

/*
Copyright (C) 2017 Fredrik Johansson
This file is part of Arb.
Arb is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "acb_dirichlet.h"
void
acb_dirichlet_hurwitz(acb_t res, const acb_t s, const acb_t a, slong prec)
{
if (acb_is_one(a))
{
acb_dirichlet_zeta(res, s, prec);
return;
}
if (acb_is_zero(s))
{
acb_mul_2exp_si(res, a, 1);
acb_sub_ui(res, res, 1, prec);
acb_neg(res, res);
acb_mul_2exp_si(res, res, -1);
return;
}
if (acb_is_int(s) && arf_sgn(arb_midref(acb_realref(s))) < 0 &&
arf_cmpabs_ui(arb_midref(acb_realref(s)), prec / 2) < 0)
{
slong n = arf_get_si(arb_midref(acb_realref(s)), ARF_RND_FLOOR);
acb_bernoulli_poly_ui(res, 1 - n, a, prec);
acb_div_si(res, res, n - 1, prec);
return;
}
if (arb_contains_zero(acb_imagref(s)) && arb_contains_si(acb_realref(s), 1))
{
acb_indeterminate(res);
return;
}
_acb_poly_zeta_cpx_series(res, s, a, 0, 1, prec);
}