73 lines
2.0 KiB
C
73 lines
2.0 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 "arith.h"
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void
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_arith_chebyshev_t_polynomial(fmpz * coeffs, ulong n)
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{
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slong k, i, d, m;
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d = n % 2;
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fmpz_zero(coeffs);
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fmpz_set_ui(coeffs + d, d ? n : 1);
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if (n % 4 >= 2)
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fmpz_neg(coeffs + d, coeffs + d);
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m = n / 2;
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for (k = 1; k <= m; k++)
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{
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i = 2 * k + d;
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fmpz_mul2_uiui(coeffs + i, coeffs + i - 2, 4*(m-k+1), n+k-m-1);
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fmpz_divexact2_uiui(coeffs + i, coeffs + i, n+2*k-2*m-1, n+2*k-2*m);
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fmpz_neg(coeffs + i, coeffs + i);
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fmpz_zero(coeffs + i - 1);
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}
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}
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void
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arith_chebyshev_t_polynomial(fmpz_poly_t poly, ulong n)
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{
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if (n == 0)
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{
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fmpz_poly_set_ui(poly, UWORD(1));
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return;
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}
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fmpz_poly_fit_length(poly, n + 1);
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if (n == 1)
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{
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fmpz_zero(poly->coeffs);
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fmpz_one(poly->coeffs + 1);
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}
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else
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_arith_chebyshev_t_polynomial(poly->coeffs, n);
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_fmpz_poly_set_length(poly, n + 1);
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}
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