void
acb_polygamma(acb_t res, const acb_t s, const acb_t z, long prec)
{
if (acb_is_zero(s))
{
acb_digamma(res, z, prec);
}
else if (acb_is_int(s) && arb_is_positive(acb_realref(s)))
{
acb_t t, u;
acb_init(t);
acb_init(u);
acb_add_ui(t, s, 1, prec);
acb_gamma(u, t, prec);
acb_hurwitz_zeta(t, t, z, prec);
if (arf_is_int_2exp_si(arb_midref(acb_realref(s)), 1))
acb_neg(t, t);
acb_mul(res, t, u, prec);
acb_clear(t);
acb_clear(u);
}
else
{
acb_t t, u;
acb_struct v[2];
acb_init(t);
acb_init(u);
acb_init(v);
acb_init(v + 1);
/* u = psi(-s) + gamma */
acb_neg(t, s);
acb_digamma(u, t, prec);
arb_const_euler(acb_realref(v), prec);
arb_add(acb_realref(u), acb_realref(u), acb_realref(v), prec);
acb_add_ui(t, s, 1, prec);
_acb_poly_zeta_cpx_series(v, t, z, 0, 2, prec);
acb_addmul(v + 1, v, u, prec);
acb_neg(t, s);
acb_rgamma(u, t, prec);
acb_mul(res, v + 1, u, prec);
acb_clear(v);
acb_clear(v + 1);
acb_clear(t);
acb_clear(u);
}
}
void
acb_dirichlet_l(acb_t res, const acb_t s,
const acb_dirichlet_group_t G, ulong m, slong prec)
{
acb_t chi, t, u, a;
ulong k;
acb_init(chi);
acb_init(t);
acb_init(u);
acb_init(a);
acb_zero(t);
for (k = 1; k <= G->q; k++)
{
acb_dirichlet_chi(chi, G, m, k, prec);
if (!acb_is_zero(chi))
{
acb_set_ui(a, k);
acb_div_ui(a, a, G->q, prec);
acb_hurwitz_zeta(u, s, a, prec);
acb_addmul(t, chi, u, prec);
}
}
acb_set_ui(u, G->q);
acb_neg(a, s);
acb_pow(u, u, a, prec);
acb_mul(res, t, u, prec);
acb_clear(chi);
acb_clear(t);
acb_clear(u);
acb_clear(a);
}
/* todo: use euler product for complex s, and check efficiency
for large negative integers */
void
acb_dirichlet_zeta(acb_t res, const acb_t s, slong prec)
{
acb_t a;
double cutoff;
if (acb_is_int(s) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(s)), FLINT_BITS - 1) < 0)
{
acb_zeta_si(res, arf_get_si(arb_midref(acb_realref(s)), ARF_RND_DOWN), prec);
return;
}
cutoff = 24.0 * prec * sqrt(prec);
if (arf_cmpabs_d(arb_midref(acb_imagref(s)), cutoff) >= 0 &&
arf_cmpabs_d(arb_midref(acb_realref(s)), 10 + prec * 0.1) <= 0)
{
acb_dirichlet_zeta_rs(res, s, 0, prec);
return;
}
acb_init(a);
acb_one(a);
if (arf_sgn(arb_midref(acb_realref(s))) < 0)
{
acb_t t, u, v;
slong wp = prec + 6;
acb_init(t);
acb_init(u);
acb_init(v);
acb_sub_ui(t, s, 1, wp);
/* 2 * (2pi)^(s-1) */
arb_const_pi(acb_realref(u), wp);
acb_mul_2exp_si(u, u, 1);
acb_pow(u, u, t, wp);
acb_mul_2exp_si(u, u, 1);
/* sin(pi*s/2) */
acb_mul_2exp_si(v, s, -1);
acb_sin_pi(v, v, wp);
acb_mul(u, u, v, wp);
/* gamma(1-s) zeta(1-s) */
acb_neg(t, t);
acb_gamma(v, t, wp);
acb_mul(u, u, v, wp);
acb_hurwitz_zeta(v, t, a, wp);
acb_mul(res, u, v, prec);
acb_clear(t);
acb_clear(u);
acb_clear(v);
}
else
{
acb_hurwitz_zeta(res, s, a, prec);
}
acb_clear(a);
}
void
acb_dirichlet_hurwitz_precomp_init(acb_dirichlet_hurwitz_precomp_t pre,
const acb_t s, int deflate, slong A, slong K, slong N, slong prec)
{
slong i, k;
if (A < 1 || K < 1 || N < 1)
abort();
pre->deflate = deflate;
pre->A = A;
pre->K = K;
pre->N = N;
pre->coeffs = _acb_vec_init(N * K);
mag_init(&pre->err);
acb_init(&pre->s);
acb_set(&pre->s, s);
acb_dirichlet_hurwitz_precomp_bound(&pre->err, s, A, K, N);
if (mag_is_finite(&pre->err))
{
acb_t t, a;
acb_init(t);
acb_init(a);
/* (-1)^k (s)_k / k! */
acb_one(pre->coeffs + 0);
for (k = 1; k < K; k++)
{
acb_add_ui(pre->coeffs + k, s, k - 1, prec);
acb_mul(pre->coeffs + k, pre->coeffs + k, pre->coeffs + k - 1, prec);
acb_div_ui(pre->coeffs + k, pre->coeffs + k, k, prec);
acb_neg(pre->coeffs + k, pre->coeffs + k);
}
for (i = 1; i < N; i++)
_acb_vec_set(pre->coeffs + i * K, pre->coeffs, K);
/* zeta(s+k,a) where a = A + (2*i+1)/(2*N) */
for (i = 0; i < N; i++)
{
acb_set_ui(a, 2 * i + 1);
acb_div_ui(a, a, 2 * N, prec);
acb_add_ui(a, a, A, prec);
for (k = 0; k < K; k++)
{
acb_add_ui(t, s, k, prec);
if (deflate && k == 0)
_acb_poly_zeta_cpx_series(t, t, a, 1, 1, prec);
else
acb_hurwitz_zeta(t, t, a, prec);
acb_mul(pre->coeffs + i * K + k,
pre->coeffs + i * K + k, t, prec);
}
}
acb_clear(t);
acb_clear(a);
}
}
int main()
{
slong iter;
flint_rand_t state;
flint_printf("hurwitz_zeta....");
fflush(stdout);
flint_randinit(state);
for (iter = 0; iter < 1000 * arb_test_multiplier(); iter++)
{
arb_t a, b, c;
acb_t d, e, f;
slong prec;
prec = 2 + n_randint(state, 300);
arb_init(a);
arb_init(b);
arb_init(c);
acb_init(d);
acb_init(e);
acb_init(f);
arb_randtest_precise(a, state, 1 + n_randint(state, 300), 5);
arb_randtest_precise(b, state, 1 + n_randint(state, 300), 5);
arb_randtest_precise(c, state, 1 + n_randint(state, 300), 5);
acb_set_arb(d, a);
acb_set_arb(e, b);
arb_hurwitz_zeta(c, a, b, prec);
acb_hurwitz_zeta(f, d, e, prec);
if (!arb_overlaps(c, acb_realref(f)) ||
(arb_is_finite(c) && !arb_contains_zero(acb_imagref(f))))
{
flint_printf("FAIL: overlap\n\n");
flint_printf("a = "); arb_printd(a, 15); flint_printf("\n\n");
flint_printf("b = "); arb_printd(b, 15); flint_printf("\n\n");
flint_printf("c = "); arb_printd(c, 15); flint_printf("\n\n");
flint_printf("d = "); acb_printd(d, 15); flint_printf("\n\n");
flint_printf("e = "); acb_printd(e, 15); flint_printf("\n\n");
flint_printf("f = "); acb_printd(f, 15); flint_printf("\n\n");
flint_abort();
}
arb_clear(a);
arb_clear(b);
arb_clear(c);
acb_clear(d);
acb_clear(e);
acb_clear(f);
}
flint_randclear(state);
flint_cleanup();
flint_printf("PASS\n");
return EXIT_SUCCESS;
}
