120 lines
3.2 KiB
C
120 lines
3.2 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 Sebastian Pancratz
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******************************************************************************/
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#include "fmpz_poly.h"
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slong _fmpz_poly_hensel_start_lift(fmpz_poly_factor_t lifted_fac, slong *link,
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fmpz_poly_t *v, fmpz_poly_t *w, const fmpz_poly_t f,
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const nmod_poly_factor_t local_fac, slong N)
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{
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const slong r = local_fac->num;
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slong i, preve;
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fmpz_t p, P;
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fmpz_poly_t monic_f;
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fmpz_init(p);
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fmpz_init(P);
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fmpz_poly_init(monic_f);
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fmpz_set_ui(p, (local_fac->p + 0)->mod.n);
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fmpz_pow_ui(P, p, N);
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if (fmpz_is_one(fmpz_poly_lead(f)))
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{
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fmpz_poly_set(monic_f, f);
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}
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else if (fmpz_cmp_si(fmpz_poly_lead(f), -1) == 0)
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{
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fmpz_poly_neg(monic_f, f);
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}
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else
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{
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fmpz_t t;
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fmpz_init(t);
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fmpz_mod(t, fmpz_poly_lead(f), P);
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if (fmpz_invmod(t, t, P) == 0)
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{
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flint_printf("Exception (fmpz_poly_start_hensel_lift).\n");
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abort();
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}
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fmpz_poly_scalar_mul_fmpz(monic_f, f, t);
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fmpz_poly_scalar_mod_fmpz(monic_f, monic_f, P);
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fmpz_clear(t);
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}
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fmpz_poly_hensel_build_tree(link, v, w, local_fac);
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{
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slong *e, n = FLINT_CLOG2(N) + 1;
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e = flint_malloc(n * sizeof(slong));
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for (e[i = 0] = N; e[i] > 1; i++)
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e[i + 1] = (e[i] + 1) / 2;
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for (i--; i > 0; i--)
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{
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fmpz_poly_hensel_lift_tree(link, v, w, monic_f, r,
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p, e[i+1], e[i], 1);
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}
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if (N > 1)
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{
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fmpz_poly_hensel_lift_tree(link, v, w, monic_f, r,
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p, e[i+1], e[i], 0);
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}
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preve = e[i+1];
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flint_free(e);
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}
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/*
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Now everything is lifted to p^N, we just need to
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insert the factors into their correct places in lifted_fac.
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*/
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fmpz_poly_factor_fit_length(lifted_fac, r);
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for (i = 0; i < 2*r - 2; i++)
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{
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if (link[i] < 0)
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{
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fmpz_poly_scalar_smod_fmpz(lifted_fac->p + (- link[i] - 1), v[i], P);
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lifted_fac->exp[- link[i] - 1] = WORD(1);
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}
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}
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lifted_fac->num = r;
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fmpz_clear(p);
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fmpz_clear(P);
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fmpz_poly_clear(monic_f);
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return preve;
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}
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