pqc/external/flint-2.4.3/fmpz_poly/div_preinv.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) 2013 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
void
_fmpz_poly_div_preinv(fmpz * Q, const fmpz * A, slong len1_in,
const fmpz * B, const fmpz * B_inv, slong len2)
{
slong len1 = len1_in;
slong n = len1 - len2 + 1;
fmpz * A_rev;
fmpz * a;
if (n > len2)
{
a = _fmpz_vec_init(len1_in);
_fmpz_vec_set(a, A, len1_in);
do {
slong start = n - len2;
_fmpz_poly_divrem_preinv(Q + start, a + start, len1 - start,
B, B_inv, len2);
n -= len2;
len1 -= len2;
} while (n > len2);
} else
a = (fmpz *) A;
A_rev = _fmpz_vec_init(len1);
_fmpz_poly_reverse(A_rev, a, len1, len1);
_fmpz_poly_mullow(Q, A_rev, len1, B_inv, len2, n);
_fmpz_poly_reverse(Q, Q, n, n);
if (a != A)
_fmpz_vec_clear(a, len1_in);
_fmpz_vec_clear(A_rev, len1);
}
void
fmpz_poly_div_preinv(fmpz_poly_t Q, const fmpz_poly_t A,
const fmpz_poly_t B, const fmpz_poly_t B_inv)
{
fmpz_poly_t tQ;
fmpz *q;
slong len1 = A->length, len2 = B_inv->length;
slong qlen = len1 - len2 + 1;
if (len1 < len2)
{
fmpz_poly_zero(Q);
return;
}
if (Q == A || Q == B || Q == B_inv)
{
fmpz_poly_init2(tQ, qlen);
q = tQ->coeffs;
}
else
{
fmpz_poly_fit_length(Q, qlen);
q = Q->coeffs;
}
_fmpz_poly_div_preinv(q, A->coeffs, len1, B->coeffs, B_inv->coeffs, len2);
if (Q == A || Q == B || Q == B_inv)
{
_fmpz_poly_set_length(tQ, qlen);
fmpz_poly_swap(tQ, Q);
fmpz_poly_clear(tQ);
}
else
_fmpz_poly_set_length(Q, qlen);
/* no need to normalise */
}