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1// Copyright (c) 2006 Xiaogang Zhang
2// Use, modification and distribution are subject to the
3// Boost Software License, Version 1.0. (See accompanying file
4// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
5
6#ifndef BOOST_MATH_BESSEL_K1_HPP
7#define BOOST_MATH_BESSEL_K1_HPP
8
9#ifdef _MSC_VER
10#pragma once
11#pragma warning(push)
12#pragma warning(disable:4702) // Unreachable code (release mode only warning)
13#endif
14
15#include <boost/math/tools/rational.hpp>
16#include <boost/math/tools/big_constant.hpp>
17#include <boost/math/policies/error_handling.hpp>
18#include <boost/assert.hpp>
19
20// Modified Bessel function of the second kind of order one
21// minimax rational approximations on intervals, see
22// Russon and Blair, Chalk River Report AECL-3461, 1969
23
24namespace boost { namespace math { namespace detail{
25
26template <typename T, typename Policy>
27T bessel_k1(T x, const Policy&);
28
29template <class T, class Policy>
30struct bessel_k1_initializer
31{
32 struct init
33 {
34 init()
35 {
36 do_init();
37 }
38 static void do_init()
39 {
40 bessel_k1(T(1), Policy());
41 }
42 void force_instantiate()const{}
43 };
44 static const init initializer;
45 static void force_instantiate()
46 {
47 initializer.force_instantiate();
48 }
49};
50
51template <class T, class Policy>
52const typename bessel_k1_initializer<T, Policy>::init bessel_k1_initializer<T, Policy>::initializer;
53
54template <typename T, typename Policy>
55T bessel_k1(T x, const Policy& pol)
56{
57 bessel_k1_initializer<T, Policy>::force_instantiate();
58
59 static const T P1[] = {
60 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -2.2149374878243304548e+06)),
61 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 7.1938920065420586101e+05)),
62 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.7733324035147015630e+05)),
63 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 7.1885382604084798576e+03)),
64 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 9.9991373567429309922e+01)),
65 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 4.8127070456878442310e-01))
66 };
67 static const T Q1[] = {
68 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -2.2149374878243304548e+06)),
69 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 3.7264298672067697862e+04)),
70 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -2.8143915754538725829e+02)),
71 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.0))
72 };
73 static const T P2[] = {
74 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 0.0)),
75 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -1.3531161492785421328e+06)),
76 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -1.4758069205414222471e+05)),
77 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -4.5051623763436087023e+03)),
78 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -5.3103913335180275253e+01)),
79 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -2.2795590826955002390e-01))
80 };
81 static const T Q2[] = {
82 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -2.7062322985570842656e+06)),
83 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 4.3117653211351080007e+04)),
84 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, -3.0507151578787595807e+02)),
85 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.0))
86 };
87 static const T P3[] = {
88 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 2.2196792496874548962e+00)),
89 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 4.4137176114230414036e+01)),
90 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 3.4122953486801312910e+02)),
91 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.3319486433183221990e+03)),
92 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 2.8590657697910288226e+03)),
93 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 3.4540675585544584407e+03)),
94 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 2.3123742209168871550e+03)),
95 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 8.1094256146537402173e+02)),
96 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.3182609918569941308e+02)),
97 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 7.5584584631176030810e+00)),
98 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 6.4257745859173138767e-02))
99 };
100 static const T Q3[] = {
101 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.7710478032601086579e+00)),
102 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 3.4552228452758912848e+01)),
103 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 2.5951223655579051357e+02)),
104 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 9.6929165726802648634e+02)),
105 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.9448440788918006154e+03)),
106 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 2.1181000487171943810e+03)),
107 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.2082692316002348638e+03)),
108 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 3.3031020088765390854e+02)),
109 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 3.6001069306861518855e+01)),
110 static_cast<T>(BOOST_MATH_BIG_CONSTANT(T, 64, 1.0))
111 };
112 T value, factor, r, r1, r2;
113
114 BOOST_MATH_STD_USING
115 using namespace boost::math::tools;
116
117 static const char* function = "boost::math::bessel_k1<%1%>(%1%,%1%)";
118
119 if (x < 0)
120 {
121 return policies::raise_domain_error<T>(function,
122 "Got x = %1%, but argument x must be non-negative, complex number result not supported.", x, pol);
123 }
124 if (x == 0)
125 {
126 return policies::raise_overflow_error<T>(function, 0, pol);
127 }
128 if (x <= 1) // x in (0, 1]
129 {
130 T y = x * x;
131 r1 = evaluate_polynomial(P1, y) / evaluate_polynomial(Q1, y);
132 r2 = evaluate_polynomial(P2, y) / evaluate_polynomial(Q2, y);
133 factor = log(x);
134 value = (r1 + factor * r2) / x;
135 }
136 else // x in (1, \infty)
137 {
138 T y = 1 / x;
139 r = evaluate_polynomial(P3, y) / evaluate_polynomial(Q3, y);
140 factor = exp(-x) / sqrt(x);
141 value = factor * r;
142 }
143
144 return value;
145}
146
147}}} // namespaces
148
149#ifdef _MSC_VER
150#pragma warning(pop)
151#endif
152
153#endif // BOOST_MATH_BESSEL_K1_HPP
154