pqc/external/flint-2.4.3/nmod_poly/log_series.c
2014-05-24 23:16:06 +02:00

99 lines
2.8 KiB
C

/*=============================================================================
This file is part of FLINT.
FLINT 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.
FLINT 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 FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 Fredrik Johansson
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
void
_nmod_poly_log_series(mp_ptr res, mp_srcptr f, slong n, nmod_t mod)
{
mp_ptr f_diff;
mp_ptr f_inv;
f_diff = _nmod_vec_init(n);
f_inv = _nmod_vec_init(n);
_nmod_poly_derivative(f_diff, f, n, mod); f_diff[n-1] = UWORD(0);
_nmod_poly_inv_series(f_inv, f, n, mod);
_nmod_poly_mullow(res, f_diff, n - 1, f_inv, n - 1, n - 1, mod);
_nmod_poly_integral(res, res, n, mod);
_nmod_vec_clear(f_diff);
_nmod_vec_clear(f_inv);
}
void
nmod_poly_log_series(nmod_poly_t res, const nmod_poly_t f, slong n)
{
mp_ptr f_coeffs;
slong k;
slong flen = f->length;
if (flen < 1 || f->coeffs[0] != UWORD(1))
{
flint_printf("Exception (nmod_poly_log_series). Constant term != 1.\n");
abort();
}
if (flen == 1 || n < 2)
{
nmod_poly_zero(res);
return;
}
nmod_poly_fit_length(res, n);
/* Efficiently handle monomials */
for (k = 1; f->coeffs[k] == UWORD(0) && k < n - 1; k++);
if (k == flen - 1 || k == n - 1)
{
flen = FLINT_MIN(flen, n);
_nmod_poly_log_series_monomial_ui(res->coeffs,
f->coeffs[flen-1], flen - 1, n, res->mod);
}
else
{
if (flen < n)
{
f_coeffs = _nmod_vec_init(n);
flint_mpn_copyi(f_coeffs, f->coeffs, flen);
flint_mpn_zero(f_coeffs + flen, n - flen);
}
else
f_coeffs = f->coeffs;
_nmod_poly_log_series(res->coeffs, f_coeffs, n, res->mod);
if (flen < n)
_nmod_vec_clear(f_coeffs);
}
res->length = n;
_nmod_poly_normalise(res);
}