129 lines
3.3 KiB
C
129 lines
3.3 KiB
C
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/*=============================================================================
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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 <gmp.h>
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#include "flint.h"
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#include "fmpz.h"
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#include "fmpz_poly.h"
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void fmpz_poly_hensel_build_tree(slong *link, fmpz_poly_t *v, fmpz_poly_t *w,
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const nmod_poly_factor_t fac)
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{
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const slong r = fac->num;
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const nmod_t mod = (fac->p + 0)->mod;
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slong i, j;
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nmod_poly_t d;
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nmod_poly_t *V = flint_malloc((2*r - 2)*sizeof(nmod_poly_t));
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nmod_poly_t *W = flint_malloc((2*r - 2)*sizeof(nmod_poly_t));
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nmod_poly_init_preinv(d, mod.n, mod.ninv);
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for (i = 0; i < 2*r - 2; i++)
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{
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nmod_poly_init_preinv(V[i], mod.n, mod.ninv);
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nmod_poly_init_preinv(W[i], mod.n, mod.ninv);
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}
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for (i = 0; i < r; i++)
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{
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nmod_poly_set(V[i], fac->p + i);
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link[i] = - i - 1;
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}
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for (i = r, j = 0; j < 2*r - 4; i++, j += 2)
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{
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slong s;
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slong minp, mind;
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slong tmp;
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minp = j;
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mind = nmod_poly_degree(V[j]);
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for (s = j+1; s < i; s++)
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{
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if (nmod_poly_degree(V[s]) < mind)
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{
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minp = s;
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mind = nmod_poly_degree(V[s]);
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}
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}
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nmod_poly_swap(V[j], V[minp]);
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/* Swap link[j] and V[minp] */
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tmp = link[j];
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link[j] = link[minp];
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link[minp] = tmp;
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minp = j+1;
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mind = nmod_poly_degree(V[j+1]);
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for (s = j + 2; s < i; s++)
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{
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if (nmod_poly_degree(V[s]) < mind)
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{
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minp = s;
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mind = nmod_poly_degree(V[s]);
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}
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}
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nmod_poly_swap(V[j + 1], V[minp]);
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/* Swap link[j+1] and V[minp] */
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tmp = link[j + 1];
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link[j+1] = link[minp];
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link[minp] = tmp;
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nmod_poly_mul(V[i], V[j], V[j+1]);
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link[i] = j;
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}
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for (j = 0; j < 2*r - 2; j += 2)
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{
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/* N.B. d == 1 */
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nmod_poly_xgcd(d, W[j], W[j+1], V[j], V[j+1]);
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}
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for (j = 0; j < 2*r - 2; j++)
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{
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fmpz_poly_set_nmod_poly(v[j], V[j]);
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fmpz_poly_set_nmod_poly(w[j], W[j]);
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}
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for (i = 0; i < 2*r - 2; i++)
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{
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nmod_poly_clear(V[i]);
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nmod_poly_clear(W[i]);
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}
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nmod_poly_clear(d);
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flint_free(V);
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flint_free(W);
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}
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