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

153 lines
4.4 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) 2008, 2009, William Hart
Copyright (C) 2010 Fredrik Johansson
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "fmpz.h"
#include "nmod_vec.h"
void
__fmpz_multi_CRT_ui_sign(fmpz_t output, const fmpz_t input,
const fmpz_comb_t comb, fmpz_t temp)
{
slong n = comb->n;
slong p;
if (n == WORD(0))
{
if (fmpz_is_zero(input))
{
fmpz_zero(output);
return;
}
/* XXX: overflow possible? */
p = comb->primes[0];
if ((p - (*input)) < (*input))
fmpz_set_si(output, (slong) ((*input) - p));
else
fmpz_set_ui(output, (*input));
return;
}
fmpz_sub(temp, input, comb->comb[comb->n - 1]);
if (fmpz_cmpabs(temp, input) <= 0)
fmpz_set(output, temp);
else
fmpz_set(output, input);
return;
}
void fmpz_multi_CRT_ui(fmpz_t output, mp_srcptr residues,
const fmpz_comb_t comb, fmpz_comb_temp_t ctemp, int sign)
{
slong i, j;
slong n = comb->n;
slong num;
slong log_res;
slong num_primes = comb->num_primes;
fmpz ** comb_temp = ctemp->comb_temp;
fmpz * temp = ctemp->temp;
fmpz * temp2 = ctemp->temp2;
/* The output is less than a single prime, so just output the result */
if (num_primes == 1)
{
if (sign)
{
mp_limb_t p = comb->primes[0];
if ((p - residues[0]) < residues[0])
fmpz_set_si(output, residues[0] - p);
else
fmpz_set_ui(output, residues[0]);
}
else
{
fmpz_set_ui(output, residues[0]);
}
return;
}
/* First layer of reconstruction */
num = (WORD(1) << n);
for (i = 0, j = 0; i + 2 <= num_primes; i += 2, j++)
{
fmpz_set_ui(temp, residues[i]);
fmpz_mod_ui(temp2, temp, comb->primes[i+1]);
fmpz_sub_ui(temp2, temp2, residues[i + 1]);
fmpz_neg(temp2, temp2);
fmpz_mul(temp, temp2, comb->res[0] + j);
fmpz_mod_ui(temp2, temp, comb->primes[i+1]);
fmpz_mul_ui(temp, temp2, comb->primes[i]);
fmpz_add_ui(comb_temp[0] + j, temp, residues[i]);
}
if (i < num_primes)
fmpz_set_ui(comb_temp[0] + j, residues[i]);
/* Compute other layers of reconstruction */
num /= 2;
log_res = 1;
while (log_res < n)
{
for (i = 0, j = 0; i < num; i += 2, j++)
{
if (fmpz_is_one(comb->comb[log_res-1] + i + 1))
{
if (!fmpz_is_one(comb->comb[log_res-1] + i))
fmpz_set(comb_temp[log_res] + j, comb_temp[log_res-1] + i);
}
else
{
fmpz_mod(temp2, comb_temp[log_res-1] + i,
comb->comb[log_res-1] + i + 1);
fmpz_sub(temp, comb_temp[log_res-1] + i + 1, temp2);
fmpz_mul(temp2, temp, comb->res[log_res] + j);
fmpz_mod(temp, temp2, comb->comb[log_res-1] + i + 1);
fmpz_mul(temp2, temp, comb->comb[log_res-1] + i);
fmpz_add(comb_temp[log_res] + j, temp2,
comb_temp[log_res-1] + i);
}
}
log_res++;
num /= 2;
}
/* Write out the output */
if (sign)
__fmpz_multi_CRT_ui_sign(output, comb_temp[log_res - 1], comb, temp);
else
fmpz_set(output, comb_temp[log_res - 1]);
}