mirror of
https://github.com/vale981/arb
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61 lines
1.2 KiB
C
61 lines
1.2 KiB
C
/*
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Copyright (C) 2015 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_poly.h"
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void
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_acb_poly_root_bound_fujiwara(mag_t bound, acb_srcptr poly, slong len)
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{
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mag_t t, u, v;
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slong i;
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if (len <= 1)
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{
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mag_inf(bound);
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return;
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}
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mag_init(t);
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mag_init(u);
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mag_init(v);
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/* u = 1/leading */
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acb_get_mag_lower(t, poly + len - 1);
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mag_one(u);
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mag_div(u, u, t);
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mag_zero(v);
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for (i = 0; i < len - 1; i++)
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{
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acb_get_mag(t, poly + len - 2 - i);
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mag_mul(t, t, u);
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if (i == len - 2)
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mag_mul_2exp_si(t, t, -1);
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mag_root(t, t, i + 1);
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mag_max(v, v, t);
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}
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mag_mul_2exp_si(bound, v, 1);
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mag_clear(t);
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mag_clear(u);
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mag_clear(v);
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}
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void
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acb_poly_root_bound_fujiwara(mag_t bound, acb_poly_t poly)
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{
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_acb_poly_root_bound_fujiwara(bound, poly->coeffs, poly->length);
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}
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