void
_acb_dirichlet_theta_arb_series(acb_t res, const dirichlet_group_t G, const dirichlet_char_t chi, const arb_t xt, slong len, slong prec)
{
acb_ptr a;
a = _acb_vec_init(len);
acb_dirichlet_chi_vec(a, G, chi, len, prec);
if (dirichlet_parity_char(G, chi))
{
slong k;
for (k = 2; k < len; k++)
acb_mul_si(a + k, a + k, k, prec);
}
acb_dirichlet_qseries_arb(res, a, xt, len, prec);
_acb_vec_clear(a, len);
}
void
acb_dirichlet_vec_mellin_arb(acb_ptr res, const dirichlet_group_t G, const dirichlet_char_t chi, slong len, const arb_t t, slong n, slong prec)
{
slong k;
arb_t tk, xt, stk, st;
acb_ptr a;
mag_t e;
a = _acb_vec_init(len);
acb_dirichlet_chi_vec(a, G, chi, len, prec);
if (dirichlet_parity_char(G, chi))
{
for (k = 2; k < len; k++)
acb_mul_si(a + k, a + k, k, prec);
}
arb_init(tk);
arb_init(xt);
arb_init(st);
arb_init(stk);
mag_init(e);
arb_sqrt(st, t, prec);
arb_one(tk);
arb_one(stk);
for (k = 0; k < n; k++)
{
_acb_dirichlet_theta_argument_at_arb(xt, G->q, tk, prec);
mag_tail_kexpk2_arb(e, xt, len);
arb_neg(xt, xt);
arb_exp(xt, xt, prec);
/* TODO: reduce len */
acb_dirichlet_qseries_arb(res + k, a, xt, len, prec);
acb_add_error_mag(res + k, e);
acb_mul_arb(res + k, res + k, stk, prec);
arb_mul(tk, tk, t, prec);
arb_mul(stk, stk, st, prec);
}
mag_clear(e);
arb_clear(xt);
arb_clear(tk);
arb_clear(stk);
arb_clear(st);
_acb_vec_clear(a, len);
}
void
acb_modular_eisenstein(acb_ptr r, const acb_t tau, slong len, slong prec)
{
psl2z_t g;
arf_t one_minus_eps;
acb_t tau_prime, t1, t2, t3, t4, q;
slong m, n;
if (len < 1)
return;
psl2z_init(g);
arf_init(one_minus_eps);
acb_init(tau_prime);
acb_init(t1);
acb_init(t2);
acb_init(t3);
acb_init(t4);
acb_init(q);
arf_set_ui_2exp_si(one_minus_eps, 63, -6);
acb_modular_fundamental_domain_approx(tau_prime, g, tau,
one_minus_eps, prec);
acb_exp_pi_i(q, tau_prime, prec);
acb_modular_theta_const_sum(t2, t3, t4, q, prec);
/* fourth powers of the theta functions (a, b, c) */
acb_mul(t2, t2, t2, prec);
acb_mul(t2, t2, t2, prec);
acb_mul(t2, t2, q, prec);
acb_mul(t3, t3, t3, prec);
acb_mul(t3, t3, t3, prec);
acb_mul(t4, t4, t4, prec);
acb_mul(t4, t4, t4, prec);
/* c2 = pi^4 * (a^8 + b^8 + c^8) / 30 */
/* c3 = pi^6 * (b^12 + c^12 - 3a^8 * (b^4+c^4)) / 180 */
/* r = a^8 */
acb_mul(r, t2, t2, prec);
if (len > 1)
{
/* r[1] = -3 a^8 * (b^4 + c^4) */
acb_add(r + 1, t3, t4, prec);
acb_mul(r + 1, r + 1, r, prec);
acb_mul_si(r + 1, r + 1, -3, prec);
}
/* b^8 */
acb_mul(t1, t3, t3, prec);
acb_add(r, r, t1, prec);
/* b^12 */
if (len > 1)
acb_addmul(r + 1, t1, t3, prec);
/* c^8 */
acb_mul(t1, t4, t4, prec);
acb_add(r, r, t1, prec);
/* c^12 */
if (len > 1)
acb_addmul(r + 1, t1, t4, prec);
acb_const_pi(t1, prec);
acb_mul(t1, t1, t1, prec);
acb_mul(t2, t1, t1, prec);
acb_mul(r, r, t2, prec);
acb_div_ui(r, r, 30, prec);
if (len > 1)
{
acb_mul(t2, t2, t1, prec);
acb_mul(r + 1, r + 1, t2, prec);
acb_div_ui(r + 1, r + 1, 189, prec);
}
/* apply modular transformation */
if (!fmpz_is_zero(&g->c))
{
acb_mul_fmpz(t1, tau, &g->c, prec);
acb_add_fmpz(t1, t1, &g->d, prec);
acb_inv(t1, t1, prec);
acb_mul(t1, t1, t1, prec);
acb_mul(t2, t1, t1, prec);
acb_mul(r, r, t2, prec);
if (len > 1)
{
acb_mul(t2, t1, t2, prec);
acb_mul(r + 1, r + 1, t2, prec);
}
}
/* compute more coefficients using recurrence */
for (n = 4; n < len + 2; n++)
{
acb_zero(r + n - 2);
m = 2;
for (m = 2; m * 2 < n; m++)
acb_addmul(r + n - 2, r + m - 2, r + n - m - 2, prec);
acb_mul_2exp_si(r + n - 2, r + n - 2, 1);
if (n % 2 == 0)
acb_addmul(r + n - 2, r + n / 2 - 2, r + n / 2 - 2, prec);
acb_mul_ui(r + n - 2, r + n - 2, 3, prec);
acb_div_ui(r + n - 2, r + n - 2, (2 * n + 1) * (n - 3), prec);
}
/* convert c's to G's */
for (n = 0; n < len; n++)
acb_div_ui(r + n, r + n, 2 * n + 3, prec);
psl2z_clear(g);
arf_clear(one_minus_eps);
acb_clear(tau_prime);
acb_clear(t1);
acb_clear(t2);
acb_clear(t3);
acb_clear(t4);
acb_clear(q);
}
int main()
{
long iter;
flint_rand_t state;
printf("lambda....");
fflush(stdout);
flint_randinit(state);
for (iter = 0; iter < 10000; iter++)
{
acb_t tau1, tau2, z1, z2, z3, t;
long e0, prec0, prec1, prec2, step;
acb_init(tau1);
acb_init(tau2);
acb_init(z1);
acb_init(z2);
acb_init(z3);
acb_init(t);
e0 = 1 + n_randint(state, 100);
prec0 = 2 + n_randint(state, 1000);
prec1 = 2 + n_randint(state, 1000);
prec2 = 2 + n_randint(state, 1000);
acb_randtest(tau1, state, prec0, e0);
acb_randtest(tau2, state, prec0, e0);
acb_randtest(z1, state, prec0, e0);
acb_randtest(z2, state, prec0, e0);
acb_set(tau2, tau1);
step = n_randint(state, 10);
/* Test invariance */
while (step --> 0)
{
if (n_randint(state, 2))
{
acb_add_ui(tau2, tau2, 2, prec0);
}
else
{
acb_mul_si(z1, tau2, -2, prec0);
acb_add_ui(z1, z1, 1, prec0);
acb_div(tau2, tau2, z1, prec0);
}
}
acb_modular_lambda(z1, tau1, prec1);
acb_modular_lambda(z2, tau2, prec2);
/* Compare with eta */
acb_mul_2exp_si(tau1, tau1, -1);
acb_modular_eta(z3, tau1, prec2);
acb_mul_2exp_si(tau1, tau1, 2);
acb_modular_eta(t, tau1, prec2);
acb_mul(t, t, t, prec2);
acb_mul(z3, z3, t, prec2);
acb_mul_2exp_si(tau1, tau1, -1);
acb_modular_eta(t, tau1, prec2);
acb_pow_ui(t, t, 3, prec2);
acb_div(z3, z3, t, prec2);
acb_pow_ui(z3, z3, 8, prec2);
acb_mul_2exp_si(z3, z3, 4);
if (!acb_overlaps(z1, z2) || !acb_overlaps(z1, z3))
{
printf("FAIL (overlap)\n");
printf("tau1 = "); acb_printd(tau1, 15); printf("\n\n");
printf("tau2 = "); acb_printd(tau2, 15); printf("\n\n");
printf("z1 = "); acb_printd(z1, 15); printf("\n\n");
printf("z2 = "); acb_printd(z2, 15); printf("\n\n");
printf("z3 = "); acb_printd(z3, 15); printf("\n\n");
abort();
}
acb_modular_lambda(tau1, tau1, prec2);
if (!acb_overlaps(z1, tau1))
{
printf("FAIL (aliasing)\n");
printf("tau1 = "); acb_printd(tau1, 15); printf("\n\n");
printf("tau2 = "); acb_printd(tau2, 15); printf("\n\n");
printf("z1 = "); acb_printd(z1, 15); printf("\n\n");
printf("z2 = "); acb_printd(z2, 15); printf("\n\n");
abort();
}
acb_clear(tau1);
acb_clear(tau2);
acb_clear(z1);
acb_clear(z2);
acb_clear(z3);
acb_clear(t);
}
flint_randclear(state);
flint_cleanup();
printf("PASS\n");
return EXIT_SUCCESS;
}
