pqc/external/flint-2.4.3/fmpz_poly/pseudo_divrem_basecase.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
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_pseudo_divrem_basecase(fmpz * Q, fmpz * R, ulong * d,
const fmpz * A, slong lenA, const fmpz * B,
slong lenB, const fmpz_preinvn_t inv)
{
const fmpz * leadB = B + (lenB - 1);
slong iQ = lenA - lenB, iR = lenA - 1;
fmpz_t rem;
fmpz_init(rem);
*d = 0;
_fmpz_vec_zero(Q, lenA - lenB + 1);
if (R != A)
_fmpz_vec_set(R, A, lenA);
while (iR >= lenB - 1)
{
if (inv)
fmpz_fdiv_qr_preinvn(Q + iQ, rem, R + iR, leadB, inv);
else
fmpz_fdiv_qr(Q + iQ, rem, R + iR, leadB);
if (!fmpz_is_zero(rem))
{
_fmpz_vec_scalar_mul_fmpz(Q, Q, lenA - lenB + 1, leadB);
fmpz_set(Q + iQ, R + iR);
_fmpz_vec_scalar_mul_fmpz(R, R, lenA, leadB);
(*d)++;
}
if (lenB > 1)
_fmpz_vec_scalar_submul_fmpz(R + (iR - lenB + 1), B, lenB - 1, Q + iQ);
fmpz_zero(R + iR);
iR--;
iQ--;
}
fmpz_clear(rem);
}
void
fmpz_poly_pseudo_divrem_basecase(fmpz_poly_t Q, fmpz_poly_t R,
ulong * d, 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_pseudo_divrem_basecase). Division by zero.\n");
abort();
}
if (Q == R)
{
flint_printf("Exception (fmpz_poly_pseudo_divrem_basecase). \n"
"Output arguments Q and R may not be aliased.\n");
abort();
}
if (A->length < B->length)
{
fmpz_poly_zero(Q);
fmpz_poly_set(R, A);
*d = 0;
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_pseudo_divrem_basecase(q, r, d, A->coeffs, A->length,
B->coeffs, B->length, NULL);
for (lenr = B->length - 2; (lenr >= 0) && !r[lenr]; lenr--) ;
lenr++;
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 = A->length;
R->length = lenr;
}
else
_fmpz_poly_set_length(R, lenr);
}