/* Copyright (C) 2015 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 . */ #include "acb_modular.h" void acb_modular_theta_const_sum(acb_t theta2, acb_t theta3, acb_t theta4, const acb_t q, slong prec) { mag_t qmag, err; double log2q_approx; int is_real, is_real_or_imag; slong N; mag_init(qmag); mag_init(err); acb_get_mag(qmag, q); log2q_approx = mag_get_d_log2_approx(qmag); is_real = arb_is_zero(acb_imagref(q)); is_real_or_imag = is_real || arb_is_zero(acb_realref(q)); if (log2q_approx >= 0.0) { N = 1; mag_inf(err); } else { N = 0; while (0.05 * N * N < prec) { if (log2q_approx * ((N+2)*(N+2)/4) < -prec - 2) break; N++; } N = (N+2)*(N+2)/4; mag_geom_series(err, qmag, N); mag_mul_2exp_si(err, err, 1); /* each term is taken twice */ if (mag_is_inf(err)) N = 1; } if (N < 1800) acb_modular_theta_const_sum_basecase(theta2, theta3, theta4, q, N, prec); else acb_modular_theta_const_sum_rs(theta2, theta3, theta4, q, N, prec); if (is_real_or_imag) arb_add_error_mag(acb_realref(theta2), err); else acb_add_error_mag(theta2, err); if (is_real) { arb_add_error_mag(acb_realref(theta3), err); arb_add_error_mag(acb_realref(theta4), err); } else { acb_add_error_mag(theta3, err); acb_add_error_mag(theta4, err); } mag_clear(qmag); mag_clear(err); }