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/*
Copyright (C) 2023 Jean Kieffer
This file is part of FLINT.
FLINT 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 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "acb.h"
#include "acb_theta.h"
void
acb_theta_g2_psi4(acb_t res, acb_srcptr th2, slong prec)
{
slong g = 2;
ulong ab;
acb_t s, t;
acb_init(s);
acb_init(t);
for (ab = 0; ab < (1 << (2 * g)); ab++)
{
if (acb_theta_char_is_even(ab, g))
{
acb_pow_ui(t, &th2[ab], 4, prec);
acb_add(s, s, t, prec);
}
}
acb_mul_2exp_si(res, s, -2);
acb_clear(s);
acb_clear(t);
}