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/*=============================================================================
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, 2010 Sebastian Pancratz
Copyright (C) 2008, 2009 William Hart
******************************************************************************/
#include <stdlib.h>
#include "fmpz_vec.h"
#include "fmpz_mod_poly.h"
void _fmpz_mod_poly_divrem_basecase(fmpz *Q, fmpz *R,
const fmpz *A, slong lenA, const fmpz *B, slong lenB,
const fmpz_t invB, const fmpz_t p)
{
slong iQ, iR;
if (R != A)
_fmpz_vec_set(R, A, lenA);
for (iQ = lenA - lenB, iR = lenA - 1; iQ >= 0; iQ--, iR--)
{
if (fmpz_is_zero(R + iR))
fmpz_zero(Q + iQ);
else
{
fmpz_mul(Q + iQ, R + iR, invB);
fmpz_mod(Q + iQ, Q + iQ, p);
_fmpz_vec_scalar_submul_fmpz(R + iQ, B, lenB, Q + iQ);
_fmpz_vec_scalar_mod_fmpz(R + iQ, R + iQ, lenB, p);
}
}
}
void fmpz_mod_poly_divrem_basecase(fmpz_mod_poly_t Q, fmpz_mod_poly_t R,
const fmpz_mod_poly_t A, const fmpz_mod_poly_t B)
{
const slong lenA = A->length, lenB = B->length, lenQ = lenA - lenB + 1;
fmpz *q, *r;
fmpz_t invB;
if (lenA < lenB)
{
fmpz_mod_poly_set(R, A);
fmpz_mod_poly_zero(Q);
return;
}
fmpz_init(invB);
fmpz_invmod(invB, B->coeffs + (lenB - 1), &(B->p));
if (Q == A || Q == B)
{
q = _fmpz_vec_init(lenQ);
}
else
{
fmpz_mod_poly_fit_length(Q, lenQ);
q = Q->coeffs;
}
if (R == B)
{
r = _fmpz_vec_init(lenA);
}
else
{
fmpz_mod_poly_fit_length(R, lenA);
r = R->coeffs;
}
_fmpz_mod_poly_divrem_basecase(q, r, A->coeffs, lenA,
B->coeffs, lenB, invB, &(B->p));
if (Q == A || Q == B)
{
_fmpz_vec_clear(Q->coeffs, Q->alloc);
Q->coeffs = q;
Q->alloc = lenQ;
Q->length = lenQ;
}
else
{
_fmpz_mod_poly_set_length(Q, lenQ);
}
if (R == B)
{
_fmpz_vec_clear(R->coeffs, R->alloc);
R->coeffs = r;
R->alloc = lenB - 1;
R->length = lenB - 1;
}
else
{
_fmpz_mod_poly_set_length(R, lenB - 1);
}
_fmpz_mod_poly_normalise(R);
fmpz_clear(invB);
}
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