mirror of
https://github.com/vale981/arb
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58 lines
1.3 KiB
C
58 lines
1.3 KiB
C
/*
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Copyright (C) 2014 Fredrik Johansson
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This file is part of Arb.
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Arb is free software: you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License (LGPL) as published
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by the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version. See <http://www.gnu.org/licenses/>.
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*/
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#include "acb.h"
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void
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acb_chebyshev_t_ui(acb_t y, ulong n, const acb_t x, slong prec)
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{
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int i, r;
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if (n <= 1)
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{
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if (n == 0)
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acb_one(y);
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else
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acb_set_round(y, x, prec);
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return;
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}
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count_trailing_zeros(r, n);
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if ((n >> r) == 1)
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{
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acb_mul(y, x, x, prec);
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acb_mul_2exp_si(y, y, 1);
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acb_sub_ui(y, y, 1, prec);
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r -= 1;
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}
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else
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{
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/* we only need one value, so break out final iteration */
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acb_t t, u;
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acb_init(t);
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acb_init(u);
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acb_chebyshev_t2_ui(t, u, (n >> (r + 1)) + 1, x, prec);
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acb_mul(t, t, u, prec);
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acb_mul_2exp_si(t, t, 1);
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acb_sub(y, t, x, prec);
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acb_clear(t);
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acb_clear(u);
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}
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for (i = 0; i < r; i++)
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{
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acb_mul(y, y, y, prec);
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acb_mul_2exp_si(y, y, 1);
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acb_sub_ui(y, y, 1, prec);
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}
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}
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