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/*
Copyright (C) 2021 Fredrik Johansson
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_hypgeom.h"
static void
bsplit(acb_t y, const acb_t x, ulong a, ulong b, slong prec)
{
if (b - a <= 4)
{
if (a == 0)
{
acb_hypgeom_rising_ui_forward(y, x, b, prec);
}
else
{
acb_add_ui(y, x, a, prec);
acb_hypgeom_rising_ui_forward(y, y, b - a, prec);
}
}
else
{
acb_t t, u;
ulong m = a + (b - a) / 2;
acb_init(t);
acb_init(u);
bsplit(t, x, a, m, prec);
bsplit(u, x, m, b, prec);
acb_mul(y, t, u, prec);
acb_clear(t);
acb_clear(u);
}
}
void
acb_hypgeom_rising_ui_bs(acb_t res, const acb_t x, ulong n, slong prec)
{
if (n <= 1)
{
if (n == 0)
acb_one(res);
else
acb_set_round(res, x, prec);
return;
}
{
acb_t t;
slong wp = ARF_PREC_ADD(prec, FLINT_BIT_COUNT(n));
acb_init(t);
bsplit(t, x, 0, n, wp);
acb_set_round(res, t, prec);
acb_clear(t);
}
}