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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_div_basecase(fmpz *Q, fmpz *R,
const fmpz *A, slong lenA, const fmpz *B, slong lenB,
const fmpz_t invB, const fmpz_t p)
{
const slong alloc = (R == NULL) ? lenA : 0;
slong lenR = lenB - 1, iQ;
if (alloc)
R = _fmpz_vec_init(alloc);
if (R != A)
_fmpz_vec_set(R + lenR, A + lenR, lenA - lenR);
for (iQ = lenA - lenB; iQ >= 0; iQ--)
{
if (fmpz_is_zero(R + lenA - 1))
{
fmpz_zero(Q + iQ);
}
else
{
fmpz_mul(Q + iQ, R + lenA - 1, invB);
fmpz_mod(Q + iQ, Q + iQ, p);
_fmpz_vec_scalar_submul_fmpz(R + lenA - lenR - 1, B, lenR, Q + iQ);
_fmpz_vec_scalar_mod_fmpz(R + lenA - lenR - 1, R + lenA - lenR - 1, lenR, p);
}
if (lenR - 1 >= iQ)
{
B++;
lenR--;
}
lenA--;
}
if (alloc)
_fmpz_vec_clear(R, alloc);
}
void fmpz_mod_poly_div_basecase(fmpz_mod_poly_t Q,
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;
fmpz_t invB;
if (lenA < lenB)
{
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;
}
_fmpz_mod_poly_div_basecase(q, NULL, 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);
}
fmpz_clear(invB);
}
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