77 lines
2.3 KiB
C
77 lines
2.3 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) 2007 David Howden
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Copyright (C) 2007, 2008, 2009, 2010 William Hart
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Copyright (C) 2008 Richard Howell-Peak
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Copyright (C) 2011 Fredrik Johansson
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******************************************************************************/
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#include "nmod_poly.h"
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void
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nmod_poly_factor_cantor_zassenhaus(nmod_poly_factor_t res, const nmod_poly_t f)
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{
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nmod_poly_t h, v, g, x;
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slong i, j, num;
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nmod_poly_init_preinv(h, f->mod.n, f->mod.ninv);
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nmod_poly_init_preinv(g, f->mod.n, f->mod.ninv);
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nmod_poly_init_preinv(v, f->mod.n, f->mod.ninv);
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nmod_poly_init_preinv(x, f->mod.n, f->mod.ninv);
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nmod_poly_set_coeff_ui(h, 1, 1);
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nmod_poly_set_coeff_ui(x, 1, 1);
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nmod_poly_make_monic(v, f);
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i = 0;
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do
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{
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i++;
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nmod_poly_powmod_ui_binexp(h, h, f->mod.n, v);
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nmod_poly_sub(h, h, x);
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nmod_poly_gcd(g, h, v);
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nmod_poly_add(h, h, x);
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if (g->length != 1)
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{
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nmod_poly_make_monic(g, g);
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num = res->num;
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nmod_poly_factor_equal_deg(res, g, i);
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for (j = num; j < res->num; j++)
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res->exp[j] = nmod_poly_remove(v, res->p + j);
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}
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}
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while (v->length >= 2*i + 3);
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if (v->length > 1)
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nmod_poly_factor_insert(res, v, 1);
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nmod_poly_clear(g);
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nmod_poly_clear(h);
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nmod_poly_clear(v);
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nmod_poly_clear(x);
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}
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