106 lines
2.7 KiB
C
106 lines
2.7 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 William Hart
|
|
|
|
******************************************************************************/
|
|
|
|
#include <stdlib.h>
|
|
#include <gmp.h>
|
|
#include "flint.h"
|
|
#include "nmod_vec.h"
|
|
#include "nmod_poly.h"
|
|
#include "ulong_extras.h"
|
|
|
|
void
|
|
_nmod_poly_inv_series_basecase(mp_ptr Qinv,
|
|
mp_srcptr Q, slong n, nmod_t mod)
|
|
{
|
|
mp_ptr X2n, Qrev;
|
|
|
|
X2n = _nmod_vec_init(2*n);
|
|
Qrev = X2n + n;
|
|
|
|
_nmod_poly_reverse(Qrev, Q, n, n);
|
|
|
|
X2n[n - 1] = 1;
|
|
flint_mpn_zero(X2n, n - 1);
|
|
X2n -= (n - 1);
|
|
|
|
_nmod_poly_div_divconquer(Qinv, X2n, 2*n - 1, Qrev, n, mod);
|
|
|
|
_nmod_poly_reverse(Qinv, Qinv, n, n);
|
|
|
|
_nmod_vec_clear(X2n + n - 1);
|
|
}
|
|
|
|
void
|
|
nmod_poly_inv_series_basecase(nmod_poly_t Qinv,
|
|
const nmod_poly_t Q, slong n)
|
|
{
|
|
mp_ptr Qinv_coeffs, Q_coeffs;
|
|
nmod_poly_t t1;
|
|
slong Qlen;
|
|
|
|
Qlen = Q->length;
|
|
|
|
if (n == 0 || Q->length == 0 || Q->coeffs[0] == 0)
|
|
{
|
|
flint_printf("Exception (nmod_poly_inv_series_basecase). Division by zero.\n");
|
|
abort();
|
|
}
|
|
|
|
if (Qlen < n)
|
|
{
|
|
Q_coeffs = _nmod_vec_init(n);
|
|
flint_mpn_copyi(Q_coeffs, Q->coeffs, Qlen);
|
|
flint_mpn_zero(Q_coeffs + Qlen, n - Qlen);
|
|
}
|
|
else
|
|
Q_coeffs = Q->coeffs;
|
|
|
|
if (Q == Qinv && Qlen >= n)
|
|
{
|
|
nmod_poly_init2(t1, Q->mod.n, n);
|
|
Qinv_coeffs = t1->coeffs;
|
|
}
|
|
else
|
|
{
|
|
nmod_poly_fit_length(Qinv, n);
|
|
Qinv_coeffs = Qinv->coeffs;
|
|
}
|
|
|
|
_nmod_poly_inv_series_basecase(Qinv_coeffs, Q_coeffs, n, Q->mod);
|
|
|
|
if (Q == Qinv && Qlen >= n)
|
|
{
|
|
nmod_poly_swap(Qinv, t1);
|
|
nmod_poly_clear(t1);
|
|
}
|
|
|
|
Qinv->length = n;
|
|
|
|
if (Qlen < n)
|
|
_nmod_vec_clear(Q_coeffs);
|
|
|
|
_nmod_poly_normalise(Qinv);
|
|
}
|