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/*
Copyright (C) 2024 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_ql_recombine(acb_ptr th, acb_srcptr th0, acb_srcptr cofactors,
const slong * pts, slong nb, const arf_t err, slong fullprec,
slong s, ulong a, int all, slong g, slong prec)
{
slong n = 1 << g;
slong n0 = 1 << s;
slong nba = 1 << (g - s);
slong nbth0 = (all ? n0 * n0 : n0);
acb_ptr aux;
acb_t x;
ulong a0, b0, b1, b;
slong k;
acb_init(x);
aux = _acb_vec_init(nbth0);
/* Sum contributions of each point weighted by cofactor */
for (k = 0; k < nb; k++)
{
_acb_vec_scalar_mul(aux, th0 + k * nbth0, nbth0, &cofactors[k], prec);
for (a0 = 0; a0 < n0; a0++)
{
if (all)
{
/* writing ab = a0 a1 b0 b1, we modify all entries with
a1 = a, with sign i^(b1 . pt) */
for (b = 0; b < n; b++)
{
b1 = b % nba;
b0 = b >> (g - s);
acb_mul_i_pow_si(x, &aux[a0 * n0 + b0],
2 * acb_theta_char_dot_slong(b1, pts + k * (g - s), g - s)
+ acb_theta_char_dot(b1, a, g - s));
acb_add(&th[(a0 << (g + g - s)) + (a << g) + b],
&th[(a0 << (g + g - s)) + (a << g) + b], x, fullprec);
}
}
else
{
acb_add(&th[(a0 << (g - s)) + a], &th[(a0 << (g - s)) + a],
&aux[a0], fullprec);
}
}
}
/* Add error */
for (a0 = 0; a0 < n0; a0++)
{
if (all)
{
for (b = 0; b < n; b++)
{
acb_add_error_arf(&th[(a0 << (g + g - s)) + (a << g) + b], err);
}
}
else
{
acb_add_error_arf(&th[(a0 << (g - s)) + a], err);
}
}
acb_clear(x);
_acb_vec_clear(aux, nbth0);
}