pqc/external/flint-2.4.3/fmpz_poly/div_root.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) 2011 Fredrik Johansson
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
void
_fmpz_poly_div_root(fmpz * Q, const fmpz * A, slong len, const fmpz_t c)
{
fmpz_t r, t;
slong i;
if (len < 2)
return;
fmpz_init(r);
fmpz_init(t);
fmpz_set(r, A + len - 1);
for (i = len - 2; i > 0; i--)
{
fmpz_mul(t, r, c);
fmpz_add(t, t, A + i);
fmpz_swap(Q + i, r);
fmpz_swap(r, t);
}
fmpz_swap(Q, r);
fmpz_clear(r);
fmpz_clear(t);
}
void
fmpz_poly_div_root(fmpz_poly_t Q, const fmpz_poly_t A, const fmpz_t c)
{
slong len = A->length;
if (len <= 1)
{
fmpz_poly_zero(Q);
return;
}
if (fmpz_is_zero(c))
{
fmpz_poly_shift_right(Q, A, 1);
return;
}
fmpz_poly_fit_length(Q, len - 1);
_fmpz_poly_div_root(Q->coeffs, A->coeffs, len, c);
_fmpz_poly_set_length(Q, len - 1);
}