pqc/external/flint-2.4.3/nmod_poly/tree.c

124 lines
3.1 KiB
C
Raw Normal View History

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 "ulong_extras.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
mp_ptr * _nmod_poly_tree_alloc(slong len)
{
mp_ptr * tree = NULL;
if (len)
{
slong i, height = FLINT_CLOG2(len);
tree = flint_malloc(sizeof(mp_ptr) * (height + 1));
for (i = 0; i <= height; i++)
tree[i] = _nmod_vec_init(len + (len >> i) + 1);
}
return tree;
}
void _nmod_poly_tree_free(mp_ptr * tree, slong len)
{
if (len)
{
slong i, height = FLINT_CLOG2(len);
for (i = 0; i <= height; i++)
flint_free(tree[i]);
flint_free(tree);
}
}
void
_nmod_poly_tree_build(mp_ptr * tree, mp_srcptr roots, slong len, nmod_t mod)
{
slong height, pow, left, i;
mp_ptr pa, pb;
if (len == 0)
return;
height = FLINT_CLOG2(len);
/* zeroth level, (x-a) */
for (i = 0; i < len; i++)
{
tree[0][2 * i + 1] = 1;
tree[0][2 * i] = nmod_neg(roots[i], mod);
}
/* first level, (x-a)(x-b) = x^2 + (-a-b)*x + a*b */
if (height > 1)
{
pa = tree[1];
for (i = 0; i < len / 2; i++)
{
mp_limb_t a, b;
a = roots[2 * i];
b = roots[2 * i + 1];
pa[3 * i] = nmod_mul(a, b, mod);
pa[3 * i + 1] = nmod_neg(nmod_add(a, b, mod), mod);
pa[3 * i + 2] = 1;
}
if (len & 1)
{
pa[3 * (len / 2)] = nmod_neg(roots[len-1], mod);
pa[3 * (len / 2) + 1] = 1;
}
}
for (i = 1; i < height - 1; i++)
{
left = len;
pow = WORD(1) << i;
pa = tree[i];
pb = tree[i + 1];
while (left >= 2 * pow)
{
_nmod_poly_mul(pb, pa, pow + 1, pa + pow + 1, pow + 1, mod);
left -= 2 * pow;
pa += 2 * pow + 2;
pb += 2 * pow + 1;
}
if (left > pow)
_nmod_poly_mul(pb, pa, pow + 1, pa + pow + 1, left - pow + 1, mod);
else if (left > 0)
_nmod_vec_set(pb, pa, left + 1);
}
}