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https://github.com/vale981/arb
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60 lines
1.3 KiB
C
60 lines
1.3 KiB
C
/*
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Copyright (C) 2021 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 "arb_hypgeom.h"
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void
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arb_hypgeom_bessel_k_integration(arb_t res, const arb_t nu, const arb_t z, int scaled, slong prec)
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{
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arb_t t, a, b, w;
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arb_init(t);
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arb_init(a);
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arb_init(b);
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arb_init(w);
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arb_one(a);
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arb_mul_2exp_si(a, a, -1);
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arb_add(a, a, nu, prec);
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arb_mul_2exp_si(b, nu, 1);
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arb_add_ui(b, b, 1, prec);
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arb_mul_2exp_si(w, z, 1);
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arb_hypgeom_u_integration(t, a, b, w, prec);
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if (arb_is_finite(t))
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{
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if (!scaled)
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{
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arb_neg(a, z);
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arb_exp(a, a, prec);
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arb_mul(t, t, a, prec);
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}
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arb_mul_2exp_si(w, z, 1);
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arb_pow(w, w, nu, prec);
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arb_mul(res, t, w, prec);
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arb_const_sqrt_pi(w, prec);
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arb_mul(res, res, w, prec);
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}
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else
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{
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arb_indeterminate(res);
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}
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arb_clear(t);
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arb_clear(a);
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arb_clear(b);
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arb_clear(w);
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}
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