pqc/external/flint-2.4.3/fmpz_mod_poly/tree.c
2014-05-24 23:16:06 +02:00

116 lines
3.4 KiB
C

/*=============================================================================
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
Copyright (C) 2012 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "fmpz_vec.h"
#include "fmpz_poly.h"
#include "fmpz_mod_poly.h"
fmpz_poly_struct ** _fmpz_mod_poly_tree_alloc(slong len)
{
fmpz_poly_struct ** tree = NULL;
if (len)
{
slong i, j, height = FLINT_CLOG2(len);
tree = flint_malloc(sizeof(fmpz_poly_struct *) * (height + 1));
for (i = 0; i <= height; i++, len = (len + 1)/2)
{
tree[i] = flint_malloc(sizeof(fmpz_poly_struct) * len);
for (j = 0; j < len; j++)
fmpz_poly_init(tree[i] + j);
}
}
return tree;
}
void _fmpz_mod_poly_tree_free(fmpz_poly_struct ** tree, slong len)
{
if (len)
{
slong i, j, height = FLINT_CLOG2(len);
for (i = 0; i <= height; i++, len = (len + 1)/2)
{
for (j = 0; j < len; j++)
fmpz_poly_clear(tree[i] + j);
flint_free(tree[i]);
}
flint_free(tree);
}
}
void
_fmpz_mod_poly_tree_build(fmpz_poly_struct ** tree, const fmpz * roots, slong len, const fmpz_t mod)
{
slong height, pow, left, i;
fmpz_poly_struct * pa, * pb;
if (len == 0)
return;
height = FLINT_CLOG2(len);
/* zeroth level, (x-a) */
for (i = 0; i < len; i++)
{
fmpz_poly_set_coeff_ui(tree[0] + i, 1, 1);
fmpz_negmod((tree[0] + i)->coeffs, roots + i, mod);
}
for (i = 0; i < height - 1; i++)
{
left = len;
pow = WORD(1) << i;
pa = tree[i];
pb = tree[i + 1];
while (left >= 2 * pow)
{
fmpz_poly_fit_length(pb, pa->length + (pa + 1)->length - 1);
_fmpz_mod_poly_mul(pb->coeffs, pa->coeffs, pa->length, (pa + 1)->coeffs, (pa + 1)->length, mod);
_fmpz_poly_set_length(pb, pa->length + (pa + 1)->length - 1);
left -= 2 * pow;
pa += 2;
pb += 1;
}
if (left > pow)
{
fmpz_poly_fit_length(pb, pa->length + (pa + 1)->length - 1);
_fmpz_mod_poly_mul(pb->coeffs, pa->coeffs, pa->length, (pa + 1)->coeffs, (pa + 1)->length, mod);
_fmpz_poly_set_length(pb, pa->length + (pa + 1)->length - 1);
} else if (left > 0)
fmpz_poly_set(pb, pa);
}
}