pqc/external/flint-2.4.3/fmpz_mod_poly/evaluate_fmpz_vec_fast.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) 2012 Fredrik Johansson
Copyright (C) 2012 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "fmpz.h"
#include "fmpz_vec.h"
#include "fmpz_mod_poly.h"
void
_fmpz_mod_poly_evaluate_fmpz_vec_fast_precomp(fmpz * vs, const fmpz * poly,
slong plen, fmpz_poly_struct * const * tree, slong len, const fmpz_t mod)
{
slong height, i, j, pow, left;
slong tree_height;
fmpz_t temp, inv;
fmpz * t, * u, * pb, * pc, * swap;
fmpz_poly_struct * pa;
fmpz_init(temp);
fmpz_init(inv);
/* avoid worrying about some degenerate cases */
if (len < 2 || plen < 2)
{
if (len == 1)
{
fmpz_negmod(temp, tree[0]->coeffs, mod);
_fmpz_mod_poly_evaluate_fmpz(vs, poly, plen, temp, mod);
} else if (len != 0 && plen == 0)
_fmpz_vec_zero(vs, len);
else if (len != 0 && plen == 1)
for (i = 0; i < len; i++)
fmpz_set(vs + i, poly);
fmpz_clear(temp);
return;
}
t = _fmpz_vec_init(2*len);
u = _fmpz_vec_init(2*len);
left = len;
/* Initial reduction. We allow the polynomial to be larger
or smaller than the number of points. */
height = FLINT_BIT_COUNT(plen - 1) - 1;
tree_height = FLINT_CLOG2(len);
while (height >= tree_height)
height--;
pow = WORD(1) << height;
for (i = j = 0; i < len; i += pow, j++)
{
pa = tree[height] + j;
fmpz_invmod(inv, pa->coeffs + pa->length - 1, mod);
_fmpz_mod_poly_rem(t + i, poly, plen, pa->coeffs, pa->length, inv, mod);
}
for (i = height - 1; i >= 0; i--)
{
pow = WORD(1) << i;
left = len;
pa = tree[i];
pb = t;
pc = u;
left = len;
while (left >= 2 * pow)
{
fmpz_invmod(inv, pa->coeffs + pa->length - 1, mod);
_fmpz_mod_poly_rem(pc, pb, 2 * pow, pa->coeffs, pa->length, inv, mod);
pa++;
fmpz_invmod(inv, pa->coeffs + pa->length - 1, mod);
_fmpz_mod_poly_rem(pc + pow, pb, 2 * pow, pa->coeffs, pa->length, inv, mod);
pa++;
pb += 2 * pow;
pc += 2 * pow;
left -= 2 * pow;
}
if (left > pow)
{
fmpz_invmod(inv, pa->coeffs + pa->length - 1, mod);
_fmpz_mod_poly_rem(pc, pb, left, pa->coeffs, pa->length, inv, mod);
pa ++;
fmpz_invmod(inv, pa->coeffs + pa->length - 1, mod);
_fmpz_mod_poly_rem(pc + pow, pb, left, pa->coeffs, pa->length, inv, mod);
}
else if (left > 0)
_fmpz_vec_set(pc, pb, left);
swap = t;
t = u;
u = swap;
}
fmpz_clear(temp);
fmpz_clear(inv);
_fmpz_vec_set(vs, t, len);
_fmpz_vec_clear(t, 2*len);
_fmpz_vec_clear(u, 2*len);
}
void _fmpz_mod_poly_evaluate_fmpz_vec_fast(fmpz * ys, const fmpz * poly, slong plen,
const fmpz * xs, slong n, const fmpz_t mod)
{
fmpz_poly_struct ** tree;
tree = _fmpz_mod_poly_tree_alloc(n);
_fmpz_mod_poly_tree_build(tree, xs, n, mod);
_fmpz_mod_poly_evaluate_fmpz_vec_fast_precomp(ys, poly, plen, tree, n, mod);
_fmpz_mod_poly_tree_free(tree, n);
}
void
fmpz_mod_poly_evaluate_fmpz_vec_fast(fmpz * ys,
const fmpz_mod_poly_t poly, const fmpz * xs, slong n)
{
_fmpz_mod_poly_evaluate_fmpz_vec_fast(ys, poly->coeffs,
poly->length, xs, n, &(poly->p));
}