pqc/external/flint-2.4.3/fmpz_poly/evaluate_divconquer_fmpz.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) 2010 Sebastian Pancratz
******************************************************************************/
#include "flint.h"
#include "fmpz.h"
#include "fmpz_vec.h"
#include "fmpz_poly.h"
void
_fmpz_poly_evaluate_divconquer_fmpz(fmpz_t res, const fmpz * poly, slong len,
const fmpz_t x)
{
slong c, h, i, k = 1;
fmpz *y, *T, *t = res, *u;
h = FLINT_BIT_COUNT(len - 1); /* 2^{h-1} < len <= 2^h */
y = _fmpz_vec_init(2 * h + 2); /* x^{2^0}, x^{2^1}, ..., x^{2^{h-1}} */
T = y + h;
u = y + 2 * h + 1;
*y = *x;
for (i = 1; i < h; i++)
fmpz_mul(y + i, y + (i - 1), y + (i - 1));
for (i = 0; i < len - 1; )
{
fmpz_mul(u, y + 0, poly + i + 1);
fmpz_add(t, poly + i, u);
i += 2;
count_trailing_zeros(c, i);
for (k = 1; k < c; k++)
{
fmpz_mul(u, y + k, t);
fmpz_add(t, T + k, u);
}
fmpz_swap(T + k, t);
}
if (len & WORD(1))
{
fmpz_set(t, poly + (len - 1));
count_trailing_zeros(c, len + 1);
for (k = 1; k < c; k++)
{
fmpz_mul(u, y + k, t);
fmpz_add(t, T + k, u);
}
fmpz_swap(T + k, t);
}
fmpz_swap(t, T + k);
for ( ; k < h; k++)
{
if ((len - 1) & (WORD(1) << k))
{
fmpz_mul(u, y + k, t);
fmpz_add(t, T + k, u);
}
}
*y = WORD(0);
_fmpz_vec_clear(y, 2 * h + 2);
}
void
fmpz_poly_evaluate_divconquer_fmpz(fmpz_t res, const fmpz_poly_t poly,
const fmpz_t a)
{
if (fmpz_poly_is_zero(poly))
{
fmpz_zero(res);
return;
}
if (res == a)
{
fmpz_t t;
fmpz_init(t);
_fmpz_poly_evaluate_divconquer_fmpz(t, poly->coeffs, poly->length, a);
fmpz_swap(res, t);
fmpz_clear(t);
}
else
_fmpz_poly_evaluate_divconquer_fmpz(res, poly->coeffs, poly->length, a);
}