118 lines
3.1 KiB
C
118 lines
3.1 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) 2010 Sebastian Pancratz
|
||
|
|
Copyright (C) 2011 Fredrik Johansson
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#include <gmp.h>
|
||
|
|
#include "flint.h"
|
||
|
|
#include "fmpz.h"
|
||
|
|
#include "fmpz_poly.h"
|
||
|
|
|
||
|
|
|
||
|
|
void
|
||
|
|
_fmpz_poly_revert_series_lagrange(fmpz * Qinv, const fmpz * Q, slong n)
|
||
|
|
{
|
||
|
|
slong i;
|
||
|
|
fmpz *R, *S, *T, *tmp;
|
||
|
|
|
||
|
|
if (n <= 2)
|
||
|
|
{
|
||
|
|
_fmpz_vec_set(Qinv, Q, n);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
R = _fmpz_vec_init(n - 1);
|
||
|
|
S = _fmpz_vec_init(n - 1);
|
||
|
|
T = _fmpz_vec_init(n - 1);
|
||
|
|
|
||
|
|
fmpz_zero(Qinv);
|
||
|
|
fmpz_set(Qinv + 1, Q + 1);
|
||
|
|
|
||
|
|
_fmpz_poly_inv_series(R, Q + 1, n - 1);
|
||
|
|
_fmpz_vec_set(S, R, n - 1);
|
||
|
|
|
||
|
|
for (i = 2; i < n; i++)
|
||
|
|
{
|
||
|
|
_fmpz_poly_mullow(T, S, n - 1, R, n - 1, n - 1);
|
||
|
|
fmpz_divexact_ui(Qinv + i, T + i - 1, i);
|
||
|
|
tmp = S; S = T; T = tmp;
|
||
|
|
}
|
||
|
|
|
||
|
|
_fmpz_vec_clear(R, n - 1);
|
||
|
|
_fmpz_vec_clear(S, n - 1);
|
||
|
|
_fmpz_vec_clear(T, n - 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
void
|
||
|
|
fmpz_poly_revert_series_lagrange(fmpz_poly_t Qinv,
|
||
|
|
const fmpz_poly_t Q, slong n)
|
||
|
|
{
|
||
|
|
fmpz *Qcopy;
|
||
|
|
int Qalloc;
|
||
|
|
slong Qlen = Q->length;
|
||
|
|
|
||
|
|
if (Qlen < 2 || !fmpz_is_zero(Q->coeffs) || !fmpz_is_pm1(Q->coeffs + 1))
|
||
|
|
{
|
||
|
|
flint_printf("Exception (fmpz_poly_revert_series_lagrange). Input must have \n"
|
||
|
|
"zero constant term and +1 or -1 as coefficient of x^1.\n");
|
||
|
|
abort();
|
||
|
|
}
|
||
|
|
|
||
|
|
if (Qlen >= n)
|
||
|
|
{
|
||
|
|
Qcopy = Q->coeffs;
|
||
|
|
Qalloc = 0;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
slong i;
|
||
|
|
Qcopy = (fmpz *) flint_malloc(n * sizeof(fmpz));
|
||
|
|
for (i = 0; i < Qlen; i++)
|
||
|
|
Qcopy[i] = Q->coeffs[i];
|
||
|
|
for ( ; i < n; i++)
|
||
|
|
Qcopy[i] = 0;
|
||
|
|
Qalloc = 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (Qinv != Q)
|
||
|
|
{
|
||
|
|
fmpz_poly_fit_length(Qinv, n);
|
||
|
|
_fmpz_poly_revert_series_lagrange(Qinv->coeffs, Qcopy, n);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
fmpz_poly_t t;
|
||
|
|
fmpz_poly_init2(t, n);
|
||
|
|
_fmpz_poly_revert_series_lagrange(t->coeffs, Qcopy, n);
|
||
|
|
fmpz_poly_swap(Qinv, t);
|
||
|
|
fmpz_poly_clear(t);
|
||
|
|
}
|
||
|
|
|
||
|
|
_fmpz_poly_set_length(Qinv, n);
|
||
|
|
_fmpz_poly_normalise(Qinv);
|
||
|
|
|
||
|
|
if (Qalloc)
|
||
|
|
flint_free(Qcopy);
|
||
|
|
}
|