147 lines
4.3 KiB
C
147 lines
4.3 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) 2011 Andy Novocin
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Copyright (C) 2011 William Hart
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Copyright (C) 2011 Sebastian Pancratz
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******************************************************************************/
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#include <stdlib.h>
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#include "fmpz_poly.h"
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#define TRACE 0
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void fmpz_poly_factor_zassenhaus_recombination(fmpz_poly_factor_t final_fac,
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const fmpz_poly_factor_t lifted_fac,
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const fmpz_poly_t F, const fmpz_t P, slong exp)
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{
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const slong r = lifted_fac->num;
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slong k, *used_arr, *sub_arr;
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fmpz_poly_t f, Q, R, tryme;
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fmpz *leadF;
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used_arr = flint_calloc(2 * r, sizeof(slong));
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sub_arr = used_arr + r;
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fmpz_poly_init(f);
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fmpz_poly_init(Q);
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fmpz_poly_init(R);
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fmpz_poly_init(tryme);
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fmpz_poly_set(f, F);
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#if TRACE == 1
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fmpz_poly_factor_print(lifted_fac); flint_printf(" lifted_fac\n");
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#endif
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leadF = fmpz_poly_lead(F);
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for (k = 1; k < r; k++)
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{
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slong count = 0, indx = k - 1, l;
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for(l = 0; l < k; l++)
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sub_arr[l] = l;
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sub_arr[indx]--;
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while ((indx >= 0))
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{
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sub_arr[indx] = sub_arr[indx] + 1;
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for (l = indx + 1; l < k; l++)
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sub_arr[l] = sub_arr[l - 1] + 1;
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if (sub_arr[k - 1] > r - 1)
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indx--;
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else
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{
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for(l = 0; l < k; l++)
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{
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if (used_arr[sub_arr[l]] == 1)
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break;
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}
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/* Need to involve leadF, perhaps set coeff 0 to leadF and do
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leadF * rest and check if under M_bits... here I'm using a
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trial division... */
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fmpz_poly_set_fmpz(tryme, leadF);
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for(l = 0; l < k; l++)
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fmpz_poly_mul(tryme, tryme, lifted_fac->p + (sub_arr[l]));
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fmpz_poly_scalar_smod_fmpz(tryme, tryme, P);
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fmpz_poly_primitive_part(tryme, tryme);
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fmpz_poly_divrem(Q, R, f, tryme);
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#if TRACE == 1
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fmpz_poly_print(tryme); flint_printf(" is tryme\n");
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fmpz_poly_print(R); flint_printf(" is R\n");
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#endif
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if (fmpz_poly_is_zero(R))
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{
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fmpz_poly_factor_insert(final_fac, tryme, exp);
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for(l = 0; l < k; l++)
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{
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used_arr[sub_arr[l]] = 1;
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count++;
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}
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fmpz_poly_set(f, Q);
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leadF = fmpz_poly_lead(f);
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/* If r - count = k then the rest are irreducible.
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TODO: Add a test for that case */
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}
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indx = k - 1;
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}
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}
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/* This is where we switch to the next loop for k. So we will have
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found all factors using <= k local factors. We should/could update
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f to be the rest divided away (or multiply the remaining), could
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also adjust r. It is the number of remaining factors so if you
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update then test if r = k or k+1 in which case the remaining f is
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irreducible. */
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}
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{
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slong test = 0;
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for (k = 0; k < r; k++)
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test = test + used_arr[k];
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if (test == 0)
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fmpz_poly_factor_insert(final_fac, f, exp);
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}
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fmpz_poly_clear(f);
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fmpz_poly_clear(tryme);
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fmpz_poly_clear(Q);
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fmpz_poly_clear(R);
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flint_free(used_arr);
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}
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#undef TRACE
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