78 lines
2.3 KiB
C
78 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) 2011 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_poly.h"
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void
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_fmpz_poly_product_roots_fmpz_vec(fmpz * poly, const fmpz * xs, slong n)
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{
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if (n == 0)
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{
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fmpz_one(poly);
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}
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else if (n < 20)
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{
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slong i, j;
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fmpz_one(poly + n);
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fmpz_neg(poly + n - 1, xs);
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for (i = 1; i < n; i++)
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{
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fmpz_mul(poly + n - i - 1, poly + n - i, xs + i);
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fmpz_neg(poly + n - i - 1, poly + n - i - 1);
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for (j = 0; j < i - 1; j++)
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fmpz_submul(poly + n - i + j, poly + n - i + j + 1, xs + i);
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fmpz_sub(poly + n - 1, poly + n - 1, xs + i);
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}
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}
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else
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{
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slong m;
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fmpz * tmp;
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m = (n + 1) / 2;
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tmp = _fmpz_vec_init(n + 2);
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_fmpz_poly_product_roots_fmpz_vec(tmp, xs, m);
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_fmpz_poly_product_roots_fmpz_vec(tmp + m + 1, xs + m, n - m);
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_fmpz_poly_mul(poly, tmp, m + 1, tmp + m + 1, n - m + 1);
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_fmpz_vec_clear(tmp, n + 2);
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}
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}
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void
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fmpz_poly_product_roots_fmpz_vec(fmpz_poly_t poly, const fmpz * xs, slong n)
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{
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fmpz_poly_fit_length(poly, n + 1);
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_fmpz_poly_product_roots_fmpz_vec(poly->coeffs, xs, n);
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_fmpz_poly_set_length(poly, n + 1);
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}
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