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

123 lines
3.3 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) 2008, 2009 William Hart
Copyright (C) 2010 Sebastian Pancratz
******************************************************************************/
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_vec.h"
#include "fmpz_poly.h"
void
_fmpz_poly_divrem_basecase(fmpz * Q, fmpz * R, const fmpz * A, slong lenA,
const fmpz * B, slong lenB)
{
const fmpz * leadB = B + (lenB - 1);
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_cmpabs(R + iR, leadB) < 0)
fmpz_zero(Q + iQ);
else
{
fmpz_fdiv_q(Q + iQ, R + iR, leadB);
_fmpz_vec_scalar_submul_fmpz(R + iQ, B, lenB, Q + iQ);
}
}
}
void
fmpz_poly_divrem_basecase(fmpz_poly_t Q, fmpz_poly_t R,
const fmpz_poly_t A, const fmpz_poly_t B)
{
slong lenq, lenr;
fmpz *q, *r;
if (B->length == 0)
{
flint_printf("Exception (fmpz_poly_divrem_basecase). Division by zero.\n");
abort();
}
if (Q == R)
{
flint_printf("Exception (fmpz_poly_divrem_basecase). \n"
"Output arguments Q and R may not be aliased.\n");
abort();
}
if (A->length < B->length)
{
fmpz_poly_set(R, A);
fmpz_poly_zero(Q);
return;
}
lenq = A->length - B->length + 1;
lenr = A->length;
if (Q == A || Q == B)
q = _fmpz_vec_init(lenq);
else
{
fmpz_poly_fit_length(Q, lenq);
q = Q->coeffs;
}
if (R == B)
r = _fmpz_vec_init(lenr);
else
{
fmpz_poly_fit_length(R, lenr);
r = R->coeffs;
}
_fmpz_poly_divrem_basecase(q, r, A->coeffs, A->length,
B->coeffs, B->length);
if (Q == A || Q == B)
{
_fmpz_vec_clear(Q->coeffs, Q->alloc);
Q->coeffs = q;
Q->alloc = lenq;
Q->length = lenq;
}
else
_fmpz_poly_set_length(Q, lenq);
if (R == B)
{
_fmpz_vec_clear(R->coeffs, R->alloc);
R->coeffs = r;
R->alloc = lenr;
R->length = lenr;
}
else
_fmpz_poly_set_length(R, lenr);
_fmpz_poly_normalise(Q);
_fmpz_poly_normalise(R);
}