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

109 lines
2.9 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_divrem_newton(mp_ptr Q, mp_ptr R, mp_srcptr A, slong lenA,
mp_srcptr B, slong lenB, nmod_t mod)
{
const slong lenQ = lenA - lenB + 1;
_nmod_poly_div_newton(Q, A, lenA, B, lenB, mod);
if (lenB > 1)
{
if (lenQ >= lenB - 1)
_nmod_poly_mullow(R, Q, lenQ, B, lenB - 1, lenB - 1, mod);
else
_nmod_poly_mullow(R, B, lenB - 1, Q, lenQ, lenB - 1, mod);
_nmod_vec_sub(R, A, R, lenB - 1, mod);
}
}
void nmod_poly_divrem_newton(nmod_poly_t Q, nmod_poly_t R,
const nmod_poly_t A, const nmod_poly_t B)
{
const slong lenA = A->length, lenB = B->length;
mp_ptr q, r;
if (lenB == 0)
{
flint_printf("Exception (nmod_poly_divrem_newton). Division by zero.\n");
abort();
}
if (lenA < lenB)
{
nmod_poly_set(R, A);
nmod_poly_zero(Q);
return;
}
if (Q == A || Q == B)
{
q = _nmod_vec_init(lenA - lenB + 1);
}
else
{
nmod_poly_fit_length(Q, lenA - lenB + 1);
q = Q->coeffs;
}
if (R == A || R == B)
{
r = _nmod_vec_init(lenB - 1);
}
else
{
nmod_poly_fit_length(R, lenB - 1);
r = R->coeffs;
}
_nmod_poly_divrem_newton(q, r, A->coeffs, lenA,
B->coeffs, lenB, B->mod);
if (Q == A || Q == B)
{
_nmod_vec_clear(Q->coeffs);
Q->coeffs = q;
Q->alloc = lenA - lenB + 1;
}
if (R == A || R == B)
{
_nmod_vec_clear(R->coeffs);
R->coeffs = r;
R->alloc = lenB - 1;
}
Q->length = lenA - lenB + 1;
R->length = lenB - 1;
_nmod_poly_normalise(R);
}