140 lines
4.0 KiB
C
140 lines
4.0 KiB
C
/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2010 Fredrik Johansson
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "fmpz.h"
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#include "fmpz_vec.h"
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#include "mpn_extras.h"
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#include "ulong_extras.h"
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void
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fmpz_factor(fmpz_factor_t factor, const fmpz_t n)
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{
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ulong exp;
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mp_limb_t p;
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__mpz_struct * xsrc;
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mp_ptr xd;
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mp_size_t xsize;
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slong found;
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slong trial_start, trial_stop;
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TMP_INIT;
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if (!COEFF_IS_MPZ(*n))
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{
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fmpz_factor_si(factor, *n);
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return;
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}
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_fmpz_factor_set_length(factor, 0);
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/* Get sign and size */
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xsrc = COEFF_TO_PTR(*n);
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if (xsrc->_mp_size < 0)
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{
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xsize = -(xsrc->_mp_size);
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factor->sign = -1;
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}
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else
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{
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xsize = xsrc->_mp_size;
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factor->sign = 1;
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}
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/* Just a single limb */
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if (xsize == 1)
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{
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_fmpz_factor_extend_factor_ui(factor, xsrc->_mp_d[0]);
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return;
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}
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/* Create a temporary copy to be mutated */
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TMP_START;
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xd = TMP_ALLOC(xsize * sizeof(mp_limb_t));
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flint_mpn_copyi(xd, xsrc->_mp_d, xsize);
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/* Factor out powers of two */
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xsize = flint_mpn_remove_2exp(xd, xsize, &exp);
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if (exp != 0)
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_fmpz_factor_append_ui(factor, UWORD(2), exp);
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trial_start = 1;
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trial_stop = 1000;
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while (xsize > 1)
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{
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found = flint_mpn_factor_trial(xd, xsize, trial_start, trial_stop);
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if (found)
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{
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p = n_primes_arr_readonly(found+1)[found];
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exp = 1;
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xsize = flint_mpn_divexact_1(xd, xsize, p);
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/* Check if p^2 divides n */
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if (flint_mpn_divisible_1_p(xd, xsize, p))
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{
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/* TODO: when searching for squarefree numbers
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(Moebius function, etc), we can abort here. */
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xsize = flint_mpn_divexact_1(xd, xsize, p);
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exp = 2;
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}
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/* If we're up to cubes, then maybe there are higher powers */
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if (exp == 2 && flint_mpn_divisible_1_p(xd, xsize, p))
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{
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xsize = flint_mpn_divexact_1(xd, xsize, p);
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xsize = flint_mpn_remove_power_ascending(xd, xsize, &p, 1, &exp);
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exp += 3;
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}
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_fmpz_factor_append_ui(factor, p, exp);
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/* flint_printf("added %wu %wu\n", p, exp); */
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/* Continue using only trial division whilst it is successful.
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This allows quickly factoring huge highly composite numbers
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such as factorials, which can arise in some applications. */
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trial_start = found + 1;
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trial_stop = trial_start + 1000;
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continue;
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}
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else
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{
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/* Insert primality test, perfect power test, other factoring
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algorithms here... */
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trial_start = trial_stop;
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trial_stop = trial_start + 1000;
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}
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}
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/* Any single-limb factor left? */
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if (xd[0] != 1)
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_fmpz_factor_extend_factor_ui(factor, xd[0]);
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TMP_END;
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return;
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}
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