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

66 lines
2.1 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
******************************************************************************/
#include "arith.h"
void
arith_bell_number_multi_mod(fmpz_t res, ulong n)
{
fmpz_comb_temp_t temp;
fmpz_comb_t comb;
nmod_t mod;
mp_ptr primes, residues;
slong k, num_primes;
mp_bitcnt_t size, prime_bits;
size = arith_bell_number_size(n);
prime_bits = FLINT_BITS - 1;
num_primes = (size + prime_bits - 1) / prime_bits;
primes = flint_malloc(num_primes * sizeof(mp_limb_t));
residues = flint_malloc(num_primes * sizeof(mp_limb_t));
primes[0] = n_nextprime(UWORD(1) << prime_bits, 0);
for (k = 1; k < num_primes; k++)
primes[k] = n_nextprime(primes[k-1], 0);
for (k = 0; k < num_primes; k++)
{
nmod_init(&mod, primes[k]);
residues[k] = arith_bell_number_nmod(n, mod);
}
fmpz_comb_init(comb, primes, num_primes);
fmpz_comb_temp_init(temp, comb);
fmpz_multi_CRT_ui(res, residues, comb, temp, 0);
fmpz_comb_clear(comb);
fmpz_comb_temp_clear(temp);
flint_free(primes);
flint_free(residues);
}