84 lines
2.2 KiB
C
84 lines
2.2 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 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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static void
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_fmpz_poly_interpolate_newton(fmpz * ys, const fmpz * xs, slong n)
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{
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fmpz_t p, q, t;
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slong i, j;
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fmpz_init(p);
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fmpz_init(q);
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fmpz_init(t);
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for (i = 1; i < n; i++)
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{
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fmpz_set(t, ys + i - 1);
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for (j = i; j < n; j++)
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{
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fmpz_sub(p, ys + j, t);
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fmpz_sub(q, xs + j, xs + j - i);
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fmpz_set(t, ys + j);
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fmpz_divexact(ys + j, p, q);
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}
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}
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fmpz_clear(p);
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fmpz_clear(q);
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fmpz_clear(t);
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}
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void
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fmpz_poly_interpolate_fmpz_vec(fmpz_poly_t poly,
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const fmpz * xs, const fmpz * ys, slong n)
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{
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if (n == 0)
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{
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fmpz_poly_zero(poly);
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return;
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}
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else if (n == 1)
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{
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fmpz_poly_set_fmpz(poly, ys);
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return;
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}
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else
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{
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fmpz_poly_fit_length(poly, n);
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_fmpz_vec_set(poly->coeffs, ys, n);
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_fmpz_poly_interpolate_newton(poly->coeffs, xs, n);
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_fmpz_poly_set_length(poly, n);
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_fmpz_poly_normalise(poly);
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_fmpz_poly_newton_to_monomial(poly->coeffs, xs, poly->length);
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}
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}
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