arb/fmpcb_poly/lgamma_series.c

118 lines
3.2 KiB
C

/*=============================================================================
This file is part of ARB.
ARB is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
ARB is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with ARB; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2013 Fredrik Johansson
******************************************************************************/
#include "fmpcb_poly.h"
#include "gamma.h"
#include "zeta.h"
void
_fmpcb_log_rising_correct_branch(fmpcb_t t,
const fmpcb_t t_wrong, const fmpcb_t z, ulong r, long prec);
static __inline__ void
_log_rising_ui_series(fmpcb_ptr t, const fmpcb_t x, long r, long len, long prec)
{
fmpcb_struct f[2];
long rflen;
fmpcb_init(f);
fmpcb_init(f + 1);
fmpcb_set(f, x);
fmpcb_one(f + 1);
rflen = FLINT_MIN(len, r + 1);
_fmpcb_poly_rising_ui_series(t, f, FLINT_MIN(2, len), r, rflen, prec);
_fmpcb_poly_log_series(t, t, rflen, len, prec);
_fmpcb_log_rising_correct_branch(t, t, x, r, prec);
fmpcb_clear(f);
fmpcb_clear(f + 1);
}
void
_fmpcb_poly_lgamma_series(fmpcb_ptr res, fmpcb_srcptr h, long hlen, long len, long prec)
{
int reflect;
long r, n, wp;
fmpcb_t zr;
fmpcb_ptr t, u;
hlen = FLINT_MIN(hlen, len);
wp = prec + FLINT_BIT_COUNT(prec);
t = _fmpcb_vec_init(len);
u = _fmpcb_vec_init(len);
fmpcb_init(zr);
/* TODO: use real code at real numbers */
if (0)
{
}
else if (len <= 2)
{
fmpcb_lgamma(u, h, wp);
if (len == 2)
fmpcb_digamma(u + 1, h, wp);
}
else
{
/* otherwise use Stirling series */
gamma_stirling_choose_param_fmpcb(&reflect, &r, &n, h, 0, 0, wp);
fmpcb_add_ui(zr, h, r, wp);
gamma_stirling_eval_fmpcb_series(u, zr, n, len, wp);
if (r != 0)
{
_log_rising_ui_series(t, h, r, len, wp);
_fmpcb_vec_sub(u, u, t, len, wp);
}
}
/* compose with nonconstant part */
fmpcb_zero(t);
_fmpcb_vec_set(t + 1, h + 1, hlen - 1);
_fmpcb_poly_compose_series(res, u, len, t, hlen, len, prec);
fmpcb_clear(zr);
_fmpcb_vec_clear(t, len);
_fmpcb_vec_clear(u, len);
}
void
fmpcb_poly_lgamma_series(fmpcb_poly_t res, const fmpcb_poly_t f, long n, long prec)
{
fmpcb_poly_fit_length(res, n);
if (f->length == 0 || n == 0)
_fmpcb_vec_indeterminate(res->coeffs, n);
else
_fmpcb_poly_lgamma_series(res->coeffs, f->coeffs, f->length, n, prec);
_fmpcb_poly_set_length(res, n);
_fmpcb_poly_normalise(res);
}