boost/math/special_functions/detail/bessel_i1.hpp
// Copyright (c) 2017 John Maddock // Use, modification and distribution are subject to the // Boost Software License, Version 1.0. (See accompanying file // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // Modified Bessel function of the first kind of order zero // we use the approximating forms derived in: // "Rational Approximations for the Modified Bessel Function of the First Kind - I1(x) for Computations with Double Precision" // by Pavel Holoborodko, // see http://www.advanpix.com/2015/11/12/rational-approximations-for-the-modified-bessel-function-of-the-first-kind-i1-for-computations-with-double-precision/ // The actual coefficients used are our own, and extend Pavel's work to precision's other than double. #ifndef BOOST_MATH_BESSEL_I1_HPP #define BOOST_MATH_BESSEL_I1_HPP #ifdef _MSC_VER #pragma once #endif #include <boost/math/tools/rational.hpp> #include <boost/math/tools/big_constant.hpp> #include <boost/math/tools/assert.hpp> #if defined(__GNUC__) && defined(BOOST_MATH_USE_FLOAT128) // // This is the only way we can avoid // warning: non-standard suffix on floating constant [-Wpedantic] // when building with -Wall -pedantic. Neither __extension__ // nor #pragma diagnostic ignored work :( // #pragma GCC system_header #endif // Modified Bessel function of the first kind of order one // minimax rational approximations on intervals, see // Blair and Edwards, Chalk River Report AECL-4928, 1974 namespace boost { namespace math { namespace detail{ template <typename T> T bessel_i1(const T& x); template <class T, class tag> struct bessel_i1_initializer { struct init { init() { do_init(tag()); } static void do_init(const std::integral_constant<int, 64>&) { bessel_i1(T(1)); bessel_i1(T(15)); bessel_i1(T(80)); bessel_i1(T(101)); } static void do_init(const std::integral_constant<int, 113>&) { bessel_i1(T(1)); bessel_i1(T(10)); bessel_i1(T(14)); bessel_i1(T(19)); bessel_i1(T(34)); bessel_i1(T(99)); bessel_i1(T(101)); } template <class U> static void do_init(const U&) {} void force_instantiate()const{} }; static const init initializer; static void force_instantiate() { initializer.force_instantiate(); } }; template <class T, class tag> const typename bessel_i1_initializer<T, tag>::init bessel_i1_initializer<T, tag>::initializer; template <typename T, int N> T bessel_i1_imp(const T&, const std::integral_constant<int, N>&) { BOOST_MATH_ASSERT(0); return 0; } template <typename T> T bessel_i1_imp(const T& x, const std::integral_constant<int, 24>&) { BOOST_MATH_STD_USING if(x < 7.75) { //Max error in interpolated form : 1.348e-08 // Max Error found at float precision = Poly : 1.469121e-07 static const float P[] = { 8.333333221e-02f, 6.944453712e-03f, 3.472097211e-04f, 1.158047174e-05f, 2.739745142e-07f, 5.135884609e-09f, 5.262251502e-11f, 1.331933703e-12f }; T a = x * x / 4; T Q[3] = { 1, 0.5f, boost::math::tools::evaluate_polynomial(P, a) }; return x * boost::math::tools::evaluate_polynomial(Q, a) / 2; } else { // Max error in interpolated form: 9.000e-08 // Max Error found at float precision = Poly: 1.044345e-07 static const float P[] = { 3.98942115977513013e-01f, -1.49581264836620262e-01f, -4.76475741878486795e-02f, -2.65157315524784407e-02f, -1.47148600683672014e-01f }; T ex = exp(x / 2); T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); result *= ex; return result; } } template <typename T> T bessel_i1_imp(const T& x, const std::integral_constant<int, 53>&) { BOOST_MATH_STD_USING if(x < 7.75) { // Bessel I0 over[10 ^ -16, 7.75] // Max error in interpolated form: 5.639e-17 // Max Error found at double precision = Poly: 1.795559e-16 static const double P[] = { 8.333333333333333803e-02, 6.944444444444341983e-03, 3.472222222225921045e-04, 1.157407407354987232e-05, 2.755731926254790268e-07, 4.920949692800671435e-09, 6.834657311305621830e-11, 7.593969849687574339e-13, 6.904822652741917551e-15, 5.220157095351373194e-17, 3.410720494727771276e-19, 1.625212890947171108e-21, 1.332898928162290861e-23 }; T a = x * x / 4; T Q[3] = { 1, 0.5f, boost::math::tools::evaluate_polynomial(P, a) }; return x * boost::math::tools::evaluate_polynomial(Q, a) / 2; } else if(x < 500) { // Max error in interpolated form: 1.796e-16 // Max Error found at double precision = Poly: 2.898731e-16 static const double P[] = { 3.989422804014406054e-01, -1.496033551613111533e-01, -4.675104253598537322e-02, -4.090895951581637791e-02, -5.719036414430205390e-02, -1.528189554374492735e-01, 3.458284470977172076e+00, -2.426181371595021021e+02, 1.178785865993440669e+04, -4.404655582443487334e+05, 1.277677779341446497e+07, -2.903390398236656519e+08, 5.192386898222206474e+09, -7.313784438967834057e+10, 8.087824484994859552e+11, -6.967602516005787001e+12, 4.614040809616582764e+13, -2.298849639457172489e+14, 8.325554073334618015e+14, -2.067285045778906105e+15, 3.146401654361325073e+15, -2.213318202179221945e+15 }; return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); } else { // Max error in interpolated form: 1.320e-19 // Max Error found at double precision = Poly: 7.065357e-17 static const double P[] = { 3.989422804014314820e-01, -1.496033551467584157e-01, -4.675105322571775911e-02, -4.090421597376992892e-02, -5.843630344778927582e-02 }; T ex = exp(x / 2); T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); result *= ex; return result; } } template <typename T> T bessel_i1_imp(const T& x, const std::integral_constant<int, 64>&) { BOOST_MATH_STD_USING if(x < 7.75) { // Bessel I0 over[10 ^ -16, 7.75] // Max error in interpolated form: 8.086e-21 // Max Error found at float80 precision = Poly: 7.225090e-20 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 64, 8.33333333333333333340071817e-02), BOOST_MATH_BIG_CONSTANT(T, 64, 6.94444444444444442462728070e-03), BOOST_MATH_BIG_CONSTANT(T, 64, 3.47222222222222318886683883e-04), BOOST_MATH_BIG_CONSTANT(T, 64, 1.15740740740738880709555060e-05), BOOST_MATH_BIG_CONSTANT(T, 64, 2.75573192240046222242685145e-07), BOOST_MATH_BIG_CONSTANT(T, 64, 4.92094986131253986838697503e-09), BOOST_MATH_BIG_CONSTANT(T, 64, 6.83465258979924922633502182e-11), BOOST_MATH_BIG_CONSTANT(T, 64, 7.59405830675154933645967137e-13), BOOST_MATH_BIG_CONSTANT(T, 64, 6.90369179710633344508897178e-15), BOOST_MATH_BIG_CONSTANT(T, 64, 5.23003610041709452814262671e-17), BOOST_MATH_BIG_CONSTANT(T, 64, 3.35291901027762552549170038e-19), BOOST_MATH_BIG_CONSTANT(T, 64, 1.83991379419781823063672109e-21), BOOST_MATH_BIG_CONSTANT(T, 64, 8.87732714140192556332037815e-24), BOOST_MATH_BIG_CONSTANT(T, 64, 3.32120654663773147206454247e-26), BOOST_MATH_BIG_CONSTANT(T, 64, 1.95294659305369207813486871e-28) }; T a = x * x / 4; T Q[3] = { 1, 0.5f, boost::math::tools::evaluate_polynomial(P, a) }; return x * boost::math::tools::evaluate_polynomial(Q, a) / 2; } else if(x < 20) { // Max error in interpolated form: 4.258e-20 // Max Error found at float80 precision = Poly: 2.851105e-19 // Maximum Deviation Found : 3.887e-20 // Expected Error Term : 3.887e-20 // Maximum Relative Change in Control Points : 1.681e-04 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 64, 3.98942260530218897338680e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -1.49599542849073670179540e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -4.70492865454119188276875e-02), BOOST_MATH_BIG_CONSTANT(T, 64, -3.12389893307392002405869e-02), BOOST_MATH_BIG_CONSTANT(T, 64, 1.49696126385202602071197e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -3.84206507612717711565967e+01), BOOST_MATH_BIG_CONSTANT(T, 64, 2.14748094784412558689584e+03), BOOST_MATH_BIG_CONSTANT(T, 64, -7.70652726663596993005669e+04), BOOST_MATH_BIG_CONSTANT(T, 64, 2.01659736164815617174439e+06), BOOST_MATH_BIG_CONSTANT(T, 64, -4.04740659606466305607544e+07), BOOST_MATH_BIG_CONSTANT(T, 64, 6.38383394696382837263656e+08), BOOST_MATH_BIG_CONSTANT(T, 64, -8.00779638649147623107378e+09), BOOST_MATH_BIG_CONSTANT(T, 64, 8.02338237858684714480491e+10), BOOST_MATH_BIG_CONSTANT(T, 64, -6.41198553664947312995879e+11), BOOST_MATH_BIG_CONSTANT(T, 64, 4.05915186909564986897554e+12), BOOST_MATH_BIG_CONSTANT(T, 64, -2.00907636964168581116181e+13), BOOST_MATH_BIG_CONSTANT(T, 64, 7.60855263982359981275199e+13), BOOST_MATH_BIG_CONSTANT(T, 64, -2.12901817219239205393806e+14), BOOST_MATH_BIG_CONSTANT(T, 64, 4.14861794397709807823575e+14), BOOST_MATH_BIG_CONSTANT(T, 64, -5.02808138522587680348583e+14), BOOST_MATH_BIG_CONSTANT(T, 64, 2.85505477056514919387171e+14) }; return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); } else if(x < 100) { // Bessel I0 over [15, 50] // Maximum Deviation Found: 2.444e-20 // Expected Error Term : 2.438e-20 // Maximum Relative Change in Control Points : 2.101e-03 // Max Error found at float80 precision = Poly : 6.029974e-20 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 64, 3.98942280401431675205845e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -1.49603355149968887210170e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -4.67510486284376330257260e-02), BOOST_MATH_BIG_CONSTANT(T, 64, -4.09071458907089270559464e-02), BOOST_MATH_BIG_CONSTANT(T, 64, -5.75278280327696940044714e-02), BOOST_MATH_BIG_CONSTANT(T, 64, -1.10591299500956620739254e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -2.77061766699949309115618e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -5.42683771801837596371638e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -9.17021412070404158464316e+00), BOOST_MATH_BIG_CONSTANT(T, 64, 1.04154379346763380543310e+02), BOOST_MATH_BIG_CONSTANT(T, 64, -1.43462345357478348323006e+03), BOOST_MATH_BIG_CONSTANT(T, 64, 9.98109660274422449523837e+03), BOOST_MATH_BIG_CONSTANT(T, 64, -3.74438822767781410362757e+04) }; return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); } else { // Bessel I0 over[100, INF] // Max error in interpolated form: 2.456e-20 // Max Error found at float80 precision = Poly: 5.446356e-20 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 64, 3.98942280401432677958445e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -1.49603355150537411254359e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -4.67510484842456251368526e-02), BOOST_MATH_BIG_CONSTANT(T, 64, -4.09071676503922479645155e-02), BOOST_MATH_BIG_CONSTANT(T, 64, -5.75256179814881566010606e-02), BOOST_MATH_BIG_CONSTANT(T, 64, -1.10754910257965227825040e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -2.67858639515616079840294e-01), BOOST_MATH_BIG_CONSTANT(T, 64, -9.17266479586791298924367e-01) }; T ex = exp(x / 2); T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); result *= ex; return result; } } template <typename T> T bessel_i1_imp(const T& x, const std::integral_constant<int, 113>&) { BOOST_MATH_STD_USING if(x < 7.75) { // Bessel I0 over[10 ^ -34, 7.75] // Max error in interpolated form: 1.835e-35 // Max Error found at float128 precision = Poly: 1.645036e-34 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 113, 8.3333333333333333333333333333333331804098e-02), BOOST_MATH_BIG_CONSTANT(T, 113, 6.9444444444444444444444444444445418303082e-03), BOOST_MATH_BIG_CONSTANT(T, 113, 3.4722222222222222222222222222119082346591e-04), BOOST_MATH_BIG_CONSTANT(T, 113, 1.1574074074074074074074074078415867655987e-05), BOOST_MATH_BIG_CONSTANT(T, 113, 2.7557319223985890652557318255143448192453e-07), BOOST_MATH_BIG_CONSTANT(T, 113, 4.9209498614260519022423916850415000626427e-09), BOOST_MATH_BIG_CONSTANT(T, 113, 6.8346525853139609753354247043900442393686e-11), BOOST_MATH_BIG_CONSTANT(T, 113, 7.5940584281266233060080535940234144302217e-13), BOOST_MATH_BIG_CONSTANT(T, 113, 6.9036894801151120925605467963949641957095e-15), BOOST_MATH_BIG_CONSTANT(T, 113, 5.2300677879659941472662086395055636394839e-17), BOOST_MATH_BIG_CONSTANT(T, 113, 3.3526075563884539394691458717439115962233e-19), BOOST_MATH_BIG_CONSTANT(T, 113, 1.8420920639497841692288943167036233338434e-21), BOOST_MATH_BIG_CONSTANT(T, 113, 8.7718669711748690065381181691546032291365e-24), BOOST_MATH_BIG_CONSTANT(T, 113, 3.6549445715236427401845636880769861424730e-26), BOOST_MATH_BIG_CONSTANT(T, 113, 1.3437296196812697924703896979250126739676e-28), BOOST_MATH_BIG_CONSTANT(T, 113, 4.3912734588619073883015937023564978854893e-31), BOOST_MATH_BIG_CONSTANT(T, 113, 1.2839967682792395867255384448052781306897e-33), BOOST_MATH_BIG_CONSTANT(T, 113, 3.3790094235693528861015312806394354114982e-36), BOOST_MATH_BIG_CONSTANT(T, 113, 8.0423861671932104308662362292359563970482e-39), BOOST_MATH_BIG_CONSTANT(T, 113, 1.7493858979396446292135661268130281652945e-41), BOOST_MATH_BIG_CONSTANT(T, 113, 3.2786079392547776769387921361408303035537e-44), BOOST_MATH_BIG_CONSTANT(T, 113, 8.2335693685833531118863552173880047183822e-47) }; T a = x * x / 4; T Q[3] = { 1, 0.5f, boost::math::tools::evaluate_polynomial(P, a) }; return x * boost::math::tools::evaluate_polynomial(Q, a) / 2; } else if(x < 11) { // Max error in interpolated form: 8.574e-36 // Maximum Deviation Found : 4.689e-36 // Expected Error Term : 3.760e-36 // Maximum Relative Change in Control Points : 5.204e-03 // Max Error found at float128 precision = Poly : 2.882561e-34 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 113, 8.333333333333333326889717360850080939e-02), BOOST_MATH_BIG_CONSTANT(T, 113, 6.944444444444444511272790848815114507e-03), BOOST_MATH_BIG_CONSTANT(T, 113, 3.472222222222221892451965054394153443e-04), BOOST_MATH_BIG_CONSTANT(T, 113, 1.157407407407408437378868534321538798e-05), BOOST_MATH_BIG_CONSTANT(T, 113, 2.755731922398566216824909767320161880e-07), BOOST_MATH_BIG_CONSTANT(T, 113, 4.920949861426434829568192525456800388e-09), BOOST_MATH_BIG_CONSTANT(T, 113, 6.834652585308926245465686943255486934e-11), BOOST_MATH_BIG_CONSTANT(T, 113, 7.594058428179852047689599244015979196e-13), BOOST_MATH_BIG_CONSTANT(T, 113, 6.903689479655006062822949671528763738e-15), BOOST_MATH_BIG_CONSTANT(T, 113, 5.230067791254403974475987777406992984e-17), BOOST_MATH_BIG_CONSTANT(T, 113, 3.352607536815161679702105115200693346e-19), BOOST_MATH_BIG_CONSTANT(T, 113, 1.842092161364672561828681848278567885e-21), BOOST_MATH_BIG_CONSTANT(T, 113, 8.771862912600611801856514076709932773e-24), BOOST_MATH_BIG_CONSTANT(T, 113, 3.654958704184380914803366733193713605e-26), BOOST_MATH_BIG_CONSTANT(T, 113, 1.343688672071130980471207297730607625e-28), BOOST_MATH_BIG_CONSTANT(T, 113, 4.392252844664709532905868749753463950e-31), BOOST_MATH_BIG_CONSTANT(T, 113, 1.282086786672692641959912811902298600e-33), BOOST_MATH_BIG_CONSTANT(T, 113, 3.408812012322547015191398229942864809e-36), BOOST_MATH_BIG_CONSTANT(T, 113, 7.681220437734066258673404589233009892e-39), BOOST_MATH_BIG_CONSTANT(T, 113, 2.072417451640733785626701738789290055e-41), BOOST_MATH_BIG_CONSTANT(T, 113, 1.352218520142636864158849446833681038e-44), BOOST_MATH_BIG_CONSTANT(T, 113, 1.407918492276267527897751358794783640e-46) }; T a = x * x / 4; T Q[3] = { 1, 0.5f, boost::math::tools::evaluate_polynomial(P, a) }; return x * boost::math::tools::evaluate_polynomial(Q, a) / 2; } else if(x < 15) { //Max error in interpolated form: 7.599e-36 // Maximum Deviation Found : 1.766e-35 // Expected Error Term : 1.021e-35 // Maximum Relative Change in Control Points : 6.228e-03 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 113, 8.333333333333255774414858563409941233e-02), BOOST_MATH_BIG_CONSTANT(T, 113, 6.944444444444897867884955912228700291e-03), BOOST_MATH_BIG_CONSTANT(T, 113, 3.472222222220954970397343617150959467e-04), BOOST_MATH_BIG_CONSTANT(T, 113, 1.157407407409660682751155024932538578e-05), BOOST_MATH_BIG_CONSTANT(T, 113, 2.755731922369973706427272809014190998e-07), BOOST_MATH_BIG_CONSTANT(T, 113, 4.920949861702265600960449699129258153e-09), BOOST_MATH_BIG_CONSTANT(T, 113, 6.834652583208361401197752793379677147e-11), BOOST_MATH_BIG_CONSTANT(T, 113, 7.594058441128280500819776168239988143e-13), BOOST_MATH_BIG_CONSTANT(T, 113, 6.903689413939268702265479276217647209e-15), BOOST_MATH_BIG_CONSTANT(T, 113, 5.230068069012898202890718644753625569e-17), BOOST_MATH_BIG_CONSTANT(T, 113, 3.352606552027491657204243201021677257e-19), BOOST_MATH_BIG_CONSTANT(T, 113, 1.842095100698532984651921750204843362e-21), BOOST_MATH_BIG_CONSTANT(T, 113, 8.771789051329870174925649852681844169e-24), BOOST_MATH_BIG_CONSTANT(T, 113, 3.655114381199979536997025497438385062e-26), BOOST_MATH_BIG_CONSTANT(T, 113, 1.343415732516712339472538688374589373e-28), BOOST_MATH_BIG_CONSTANT(T, 113, 4.396177019032432392793591204647901390e-31), BOOST_MATH_BIG_CONSTANT(T, 113, 1.277563309255167951005939802771456315e-33), BOOST_MATH_BIG_CONSTANT(T, 113, 3.449201419305514579791370198046544736e-36), BOOST_MATH_BIG_CONSTANT(T, 113, 7.415430703400740634202379012388035255e-39), BOOST_MATH_BIG_CONSTANT(T, 113, 2.195458831864936225409005027914934499e-41), BOOST_MATH_BIG_CONSTANT(T, 113, 8.829726762743879793396637797534668039e-45), BOOST_MATH_BIG_CONSTANT(T, 113, 1.698302711685624490806751012380215488e-46), BOOST_MATH_BIG_CONSTANT(T, 113, -2.062520475425422618494185821587228317e-49), BOOST_MATH_BIG_CONSTANT(T, 113, 6.732372906742845717148185173723304360e-52) }; T a = x * x / 4; T Q[3] = { 1, 0.5f, boost::math::tools::evaluate_polynomial(P, a) }; return x * boost::math::tools::evaluate_polynomial(Q, a) / 2; } else if(x < 20) { // Max error in interpolated form: 8.864e-36 // Max Error found at float128 precision = Poly: 8.522841e-35 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 113, 3.989422793693152031514179994954750043e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -1.496029423752889591425633234009799670e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -4.682975926820553021482820043377990241e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -3.138871171577224532369979905856458929e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -8.765350219426341341990447005798111212e-01), BOOST_MATH_BIG_CONSTANT(T, 113, 5.321389275507714530941178258122955540e+01), BOOST_MATH_BIG_CONSTANT(T, 113, -2.727748393898888756515271847678850411e+03), BOOST_MATH_BIG_CONSTANT(T, 113, 1.123040820686242586086564998713862335e+05), BOOST_MATH_BIG_CONSTANT(T, 113, -3.784112378374753535335272752884808068e+06), BOOST_MATH_BIG_CONSTANT(T, 113, 1.054920416060932189433079126269416563e+08), BOOST_MATH_BIG_CONSTANT(T, 113, -2.450129415468060676827180524327749553e+09), BOOST_MATH_BIG_CONSTANT(T, 113, 4.758831882046487398739784498047935515e+10), BOOST_MATH_BIG_CONSTANT(T, 113, -7.736936520262204842199620784338052937e+11), BOOST_MATH_BIG_CONSTANT(T, 113, 1.051128683324042629513978256179115439e+13), BOOST_MATH_BIG_CONSTANT(T, 113, -1.188008285959794869092624343537262342e+14), BOOST_MATH_BIG_CONSTANT(T, 113, 1.108530004906954627420484180793165669e+15), BOOST_MATH_BIG_CONSTANT(T, 113, -8.441516828490144766650287123765318484e+15), BOOST_MATH_BIG_CONSTANT(T, 113, 5.158251664797753450664499268756393535e+16), BOOST_MATH_BIG_CONSTANT(T, 113, -2.467314522709016832128790443932896401e+17), BOOST_MATH_BIG_CONSTANT(T, 113, 8.896222045367960462945885220710294075e+17), BOOST_MATH_BIG_CONSTANT(T, 113, -2.273382139594876997203657902425653079e+18), BOOST_MATH_BIG_CONSTANT(T, 113, 3.669871448568623680543943144842394531e+18), BOOST_MATH_BIG_CONSTANT(T, 113, -2.813923031370708069940575240509912588e+18) }; return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); } else if(x < 35) { // Max error in interpolated form: 6.028e-35 // Max Error found at float128 precision = Poly: 1.368313e-34 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 113, 3.989422804012941975429616956496046931e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -1.496033550576049830976679315420681402e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -4.675107835141866009896710750800622147e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -4.090104965125365961928716504473692957e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -5.842241652296980863361375208605487570e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -1.063604828033747303936724279018650633e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -9.113375972811586130949401996332817152e+00), BOOST_MATH_BIG_CONSTANT(T, 113, 6.334748570425075872639817839399823709e+02), BOOST_MATH_BIG_CONSTANT(T, 113, -3.759150758768733692594821032784124765e+04), BOOST_MATH_BIG_CONSTANT(T, 113, 1.863672813448915255286274382558526321e+06), BOOST_MATH_BIG_CONSTANT(T, 113, -7.798248643371718775489178767529282534e+07), BOOST_MATH_BIG_CONSTANT(T, 113, 2.769963173932801026451013022000669267e+09), BOOST_MATH_BIG_CONSTANT(T, 113, -8.381780137198278741566746511015220011e+10), BOOST_MATH_BIG_CONSTANT(T, 113, 2.163891337116820832871382141011952931e+12), BOOST_MATH_BIG_CONSTANT(T, 113, -4.764325864671438675151635117936912390e+13), BOOST_MATH_BIG_CONSTANT(T, 113, 8.925668307403332887856809510525154955e+14), BOOST_MATH_BIG_CONSTANT(T, 113, -1.416692606589060039334938090985713641e+16), BOOST_MATH_BIG_CONSTANT(T, 113, 1.892398600219306424294729851605944429e+17), BOOST_MATH_BIG_CONSTANT(T, 113, -2.107232903741874160308537145391245060e+18), BOOST_MATH_BIG_CONSTANT(T, 113, 1.930223393531877588898224144054112045e+19), BOOST_MATH_BIG_CONSTANT(T, 113, -1.427759576167665663373350433236061007e+20), BOOST_MATH_BIG_CONSTANT(T, 113, 8.306019279465532835530812122374386654e+20), BOOST_MATH_BIG_CONSTANT(T, 113, -3.653753000392125229440044977239174472e+21), BOOST_MATH_BIG_CONSTANT(T, 113, 1.140760686989511568435076842569804906e+22), BOOST_MATH_BIG_CONSTANT(T, 113, -2.249149337812510200795436107962504749e+22), BOOST_MATH_BIG_CONSTANT(T, 113, 2.101619088427348382058085685849420866e+22) }; return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); } else if(x < 100) { // Max error in interpolated form: 5.494e-35 // Max Error found at float128 precision = Poly: 1.214651e-34 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 113, 3.989422804014326779399307367861631577e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -1.496033551505372542086590873271571919e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -4.675104848454290286276466276677172664e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -4.090716742397105403027549796269213215e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -5.752570419098513588311026680089351230e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -1.107369803696534592906420980901195808e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -2.699214194000085622941721628134575121e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -7.953006169077813678478720427604462133e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -2.746618809476524091493444128605380593e+00), BOOST_MATH_BIG_CONSTANT(T, 113, -1.084446249943196826652788161656973391e+01), BOOST_MATH_BIG_CONSTANT(T, 113, -5.020325182518980633783194648285500554e+01), BOOST_MATH_BIG_CONSTANT(T, 113, -1.510195971266257573425196228564489134e+02), BOOST_MATH_BIG_CONSTANT(T, 113, -5.241661863814900938075696173192225056e+03), BOOST_MATH_BIG_CONSTANT(T, 113, 1.323374362891993686413568398575539777e+05), BOOST_MATH_BIG_CONSTANT(T, 113, -4.112838452096066633754042734723911040e+06), BOOST_MATH_BIG_CONSTANT(T, 113, 9.369270194978310081563767560113534023e+07), BOOST_MATH_BIG_CONSTANT(T, 113, -1.704295412488936504389347368131134993e+09), BOOST_MATH_BIG_CONSTANT(T, 113, 2.320829576277038198439987439508754886e+10), BOOST_MATH_BIG_CONSTANT(T, 113, -2.258818139077875493434420764260185306e+11), BOOST_MATH_BIG_CONSTANT(T, 113, 1.396791306321498426110315039064592443e+12), BOOST_MATH_BIG_CONSTANT(T, 113, -4.217617301585849875301440316301068439e+12) }; return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); } else { // Bessel I0 over[100, INF] // Max error in interpolated form: 6.081e-35 // Max Error found at float128 precision = Poly: 1.407151e-34 static const T P[] = { BOOST_MATH_BIG_CONSTANT(T, 113, 3.9894228040143267793994605993438200208417e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -1.4960335515053725422747977247811372936584e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -4.6751048484542891946087411826356811991039e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -4.0907167423975030452875828826630006305665e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -5.7525704189964886494791082898669060345483e-02), BOOST_MATH_BIG_CONSTANT(T, 113, -1.1073698056568248642163476807108190176386e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -2.6992139012879749064623499618582631684228e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -7.9530409594026597988098934027440110587905e-01), BOOST_MATH_BIG_CONSTANT(T, 113, -2.7462844478733532517044536719240098183686e+00), BOOST_MATH_BIG_CONSTANT(T, 113, -1.0870711340681926669381449306654104739256e+01), BOOST_MATH_BIG_CONSTANT(T, 113, -4.8510175413216969245241059608553222505228e+01), BOOST_MATH_BIG_CONSTANT(T, 113, -2.4094682286011573747064907919522894740063e+02), BOOST_MATH_BIG_CONSTANT(T, 113, -1.3128845936764406865199641778959502795443e+03), BOOST_MATH_BIG_CONSTANT(T, 113, -8.1655901321962541203257516341266838487359e+03), BOOST_MATH_BIG_CONSTANT(T, 113, -3.8019591025686295090160445920753823994556e+04), BOOST_MATH_BIG_CONSTANT(T, 113, -6.7008089049178178697338128837158732831105e+05) }; T ex = exp(x / 2); T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x); result *= ex; return result; } } template <typename T> T bessel_i1_imp(const T& x, const std::integral_constant<int, 0>&) { if(boost::math::tools::digits<T>() <= 24) return bessel_i1_imp(x, std::integral_constant<int, 24>()); else if(boost::math::tools::digits<T>() <= 53) return bessel_i1_imp(x, std::integral_constant<int, 53>()); else if(boost::math::tools::digits<T>() <= 64) return bessel_i1_imp(x, std::integral_constant<int, 64>()); else if(boost::math::tools::digits<T>() <= 113) return bessel_i1_imp(x, std::integral_constant<int, 113>()); BOOST_MATH_ASSERT(0); return 0; } template <typename T> inline T bessel_i1(const T& x) { typedef std::integral_constant<int, ((std::numeric_limits<T>::digits == 0) || (std::numeric_limits<T>::radix != 2)) ? 0 : std::numeric_limits<T>::digits <= 24 ? 24 : std::numeric_limits<T>::digits <= 53 ? 53 : std::numeric_limits<T>::digits <= 64 ? 64 : std::numeric_limits<T>::digits <= 113 ? 113 : -1 > tag_type; bessel_i1_initializer<T, tag_type>::force_instantiate(); return bessel_i1_imp(x, tag_type()); } }}} // namespaces #endif // BOOST_MATH_BESSEL_I1_HPP