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1// Copyright (c) 2006 Xiaogang Zhang2// Copyright (c) 2017 John Maddock3// Copyright (c) 2024 Matt Borland4// Use, modification and distribution are subject to the5// Boost Software License, Version 1.0. (See accompanying file6// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)7 8#ifndef BOOST_MATH_BESSEL_I0_HPP9#define BOOST_MATH_BESSEL_I0_HPP10 11#ifdef _MSC_VER12#pragma once13#endif14 15#include <boost/math/tools/rational.hpp>16#include <boost/math/tools/big_constant.hpp>17#include <boost/math/tools/assert.hpp>18#include <boost/math/tools/type_traits.hpp>19#include <boost/math/tools/numeric_limits.hpp>20#include <boost/math/tools/precision.hpp>21 22#if defined(__GNUC__) && defined(BOOST_MATH_USE_FLOAT128)23//24// This is the only way we can avoid25// warning: non-standard suffix on floating constant [-Wpedantic]26// when building with -Wall -pedantic. Neither __extension__27// nor #pragma diagnostic ignored work :(28//29#pragma GCC system_header30#endif31 32// Modified Bessel function of the first kind of order zero33// we use the approximating forms derived in:34// "Rational Approximations for the Modified Bessel Function of the First Kind - I0(x) for Computations with Double Precision"35// by Pavel Holoborodko, 36// see http://www.advanpix.com/2015/11/11/rational-approximations-for-the-modified-bessel-function-of-the-first-kind-i0-computations-double-precision37// The actual coefficients used are our own, and extend Pavel's work to precision's other than double.38 39namespace boost { namespace math { namespace detail{40 41template <typename T>42BOOST_MATH_GPU_ENABLED T bessel_i0(const T& x);43 44template <typename T, int N>45BOOST_MATH_GPU_ENABLED T bessel_i0_imp(const T&, const boost::math::integral_constant<int, N>&)46{47 BOOST_MATH_ASSERT(0);48 return 0;49}50 51template <typename T>52BOOST_MATH_GPU_ENABLED T bessel_i0_imp(const T& x, const boost::math::integral_constant<int, 24>&)53{54 BOOST_MATH_STD_USING55 if(x < 7.75)56 {57 // Max error in interpolated form: 3.929e-0858 // Max Error found at float precision = Poly: 1.991226e-0759 BOOST_MATH_STATIC const float P[] = {60 1.00000003928615375e+00f,61 2.49999576572179639e-01f,62 2.77785268558399407e-02f,63 1.73560257755821695e-03f,64 6.96166518788906424e-05f,65 1.89645733877137904e-06f,66 4.29455004657565361e-08f,67 3.90565476357034480e-10f,68 1.48095934745267240e-11f69 };70 T a = x * x / 4;71 return a * boost::math::tools::evaluate_polynomial(P, a) + 1;72 }73 else if(x < 50)74 {75 // Max error in interpolated form: 5.195e-0876 // Max Error found at float precision = Poly: 8.502534e-0877 BOOST_MATH_STATIC const float P[] = {78 3.98942651588301770e-01f,79 4.98327234176892844e-02f,80 2.91866904423115499e-02f,81 1.35614940793742178e-02f,82 1.31409251787866793e-01f83 };84 return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);85 }86 else87 {88 // Max error in interpolated form: 1.782e-0989 // Max Error found at float precision = Poly: 6.473568e-0890 BOOST_MATH_STATIC const float P[] = {91 3.98942391532752700e-01f,92 4.98455950638200020e-02f,93 2.94835666900682535e-02f94 };95 T ex = exp(x / 2);96 T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);97 result *= ex;98 return result;99 }100}101 102template <typename T>103BOOST_MATH_GPU_ENABLED T bessel_i0_imp(const T& x, const boost::math::integral_constant<int, 53>&)104{105 BOOST_MATH_STD_USING106 if(x < 7.75)107 {108 // Bessel I0 over[10 ^ -16, 7.75]109 // Max error in interpolated form : 3.042e-18110 // Max Error found at double precision = Poly : 5.106609e-16 Cheb : 5.239199e-16111 BOOST_MATH_STATIC const double P[] = {112 1.00000000000000000e+00,113 2.49999999999999909e-01,114 2.77777777777782257e-02,115 1.73611111111023792e-03,116 6.94444444453352521e-05,117 1.92901234513219920e-06,118 3.93675991102510739e-08,119 6.15118672704439289e-10,120 7.59407002058973446e-12,121 7.59389793369836367e-14,122 6.27767773636292611e-16,123 4.34709704153272287e-18,124 2.63417742690109154e-20,125 1.13943037744822825e-22,126 9.07926920085624812e-25127 };128 T a = x * x / 4;129 return a * boost::math::tools::evaluate_polynomial(P, a) + 1;130 }131 else if(x < 500)132 {133 // Max error in interpolated form : 1.685e-16134 // Max Error found at double precision = Poly : 2.575063e-16 Cheb : 2.247615e+00135 BOOST_MATH_STATIC const double P[] = {136 3.98942280401425088e-01,137 4.98677850604961985e-02,138 2.80506233928312623e-02,139 2.92211225166047873e-02,140 4.44207299493659561e-02,141 1.30970574605856719e-01,142 -3.35052280231727022e+00,143 2.33025711583514727e+02,144 -1.13366350697172355e+04,145 4.24057674317867331e+05,146 -1.23157028595698731e+07,147 2.80231938155267516e+08,148 -5.01883999713777929e+09,149 7.08029243015109113e+10,150 -7.84261082124811106e+11,151 6.76825737854096565e+12,152 -4.49034849696138065e+13,153 2.24155239966958995e+14,154 -8.13426467865659318e+14,155 2.02391097391687777e+15,156 -3.08675715295370878e+15,157 2.17587543863819074e+15158 };159 return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);160 }161 else162 {163 // Max error in interpolated form : 2.437e-18164 // Max Error found at double precision = Poly : 1.216719e-16165 BOOST_MATH_STATIC const double P[] = {166 3.98942280401432905e-01,167 4.98677850491434560e-02,168 2.80506308916506102e-02,169 2.92179096853915176e-02,170 4.53371208762579442e-02171 };172 T ex = exp(x / 2);173 T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);174 result *= ex;175 return result;176 }177}178 179template <typename T>180BOOST_MATH_GPU_ENABLED T bessel_i0_imp(const T& x, const boost::math::integral_constant<int, 64>&)181{182 BOOST_MATH_STD_USING183 if(x < 7.75)184 {185 // Bessel I0 over[10 ^ -16, 7.75]186 // Max error in interpolated form : 3.899e-20187 // Max Error found at float80 precision = Poly : 1.770840e-19188 // LCOV_EXCL_START189 BOOST_MATH_STATIC const T P[] = {190 BOOST_MATH_BIG_CONSTANT(T, 64, 9.99999999999999999961011629e-01),191 BOOST_MATH_BIG_CONSTANT(T, 64, 2.50000000000000001321873912e-01),192 BOOST_MATH_BIG_CONSTANT(T, 64, 2.77777777777777703400424216e-02),193 BOOST_MATH_BIG_CONSTANT(T, 64, 1.73611111111112764793802701e-03),194 BOOST_MATH_BIG_CONSTANT(T, 64, 6.94444444444251461247253525e-05),195 BOOST_MATH_BIG_CONSTANT(T, 64, 1.92901234569262206386118739e-06),196 BOOST_MATH_BIG_CONSTANT(T, 64, 3.93675988851131457141005209e-08),197 BOOST_MATH_BIG_CONSTANT(T, 64, 6.15118734688297476454205352e-10),198 BOOST_MATH_BIG_CONSTANT(T, 64, 7.59405797058091016449222685e-12),199 BOOST_MATH_BIG_CONSTANT(T, 64, 7.59406599631719800679835140e-14),200 BOOST_MATH_BIG_CONSTANT(T, 64, 6.27598961062070013516660425e-16),201 BOOST_MATH_BIG_CONSTANT(T, 64, 4.35920318970387940278362992e-18),202 BOOST_MATH_BIG_CONSTANT(T, 64, 2.57372492687715452949437981e-20),203 BOOST_MATH_BIG_CONSTANT(T, 64, 1.33908663475949906992942204e-22),204 BOOST_MATH_BIG_CONSTANT(T, 64, 5.15976668870980234582896010e-25),205 BOOST_MATH_BIG_CONSTANT(T, 64, 3.46240478946376069211156548e-27)206 };207 // LCOV_EXCL_STOP208 T a = x * x / 4;209 return a * boost::math::tools::evaluate_polynomial(P, a) + 1;210 }211 else if(x < 10)212 {213 // Maximum Deviation Found: 6.906e-21214 // Expected Error Term : -6.903e-21215 // Maximum Relative Change in Control Points : 1.631e-04216 // Max Error found at float80 precision = Poly : 7.811948e-21217 // LCOV_EXCL_START218 BOOST_MATH_STATIC const T Y = 4.051098823547363281250e-01f;219 BOOST_MATH_STATIC const T P[] = {220 BOOST_MATH_BIG_CONSTANT(T, 64, -6.158081780620616479492e-03),221 BOOST_MATH_BIG_CONSTANT(T, 64, 4.883635969834048766148e-02),222 BOOST_MATH_BIG_CONSTANT(T, 64, 7.892782002476195771920e-02),223 BOOST_MATH_BIG_CONSTANT(T, 64, -1.478784996478070170327e+00),224 BOOST_MATH_BIG_CONSTANT(T, 64, 2.988611837308006851257e+01),225 BOOST_MATH_BIG_CONSTANT(T, 64, -4.140133766747436806179e+02),226 BOOST_MATH_BIG_CONSTANT(T, 64, 4.117316447921276453271e+03),227 BOOST_MATH_BIG_CONSTANT(T, 64, -2.942353667455141676001e+04),228 BOOST_MATH_BIG_CONSTANT(T, 64, 1.493482682461387081534e+05),229 BOOST_MATH_BIG_CONSTANT(T, 64, -5.228100538921466124653e+05),230 BOOST_MATH_BIG_CONSTANT(T, 64, 1.195279248600467989454e+06),231 BOOST_MATH_BIG_CONSTANT(T, 64, -1.601530760654337045917e+06),232 BOOST_MATH_BIG_CONSTANT(T, 64, 9.504921137873298402679e+05)233 };234 // LCOV_EXCL_STOP235 return exp(x) * (boost::math::tools::evaluate_polynomial(P, T(1 / x)) + Y) / sqrt(x);236 }237 else if(x < 15)238 {239 // Maximum Deviation Found: 4.083e-21240 // Expected Error Term : -4.025e-21241 // Maximum Relative Change in Control Points : 1.304e-03242 // Max Error found at float80 precision = Poly : 2.303527e-20243 // LCOV_EXCL_START244 BOOST_MATH_STATIC const T Y = 4.033188819885253906250e-01f;245 BOOST_MATH_STATIC const T P[] = {246 BOOST_MATH_BIG_CONSTANT(T, 64, -4.376373876116109401062e-03),247 BOOST_MATH_BIG_CONSTANT(T, 64, 4.982899138682911273321e-02),248 BOOST_MATH_BIG_CONSTANT(T, 64, 3.109477529533515397644e-02),249 BOOST_MATH_BIG_CONSTANT(T, 64, -1.163760580110576407673e-01),250 BOOST_MATH_BIG_CONSTANT(T, 64, 4.776501832837367371883e+00),251 BOOST_MATH_BIG_CONSTANT(T, 64, -1.101478069227776656318e+02),252 BOOST_MATH_BIG_CONSTANT(T, 64, 1.892071912448960299773e+03),253 BOOST_MATH_BIG_CONSTANT(T, 64, -2.417739279982328117483e+04),254 BOOST_MATH_BIG_CONSTANT(T, 64, 2.296963447724067390552e+05),255 BOOST_MATH_BIG_CONSTANT(T, 64, -1.598589306710589358747e+06),256 BOOST_MATH_BIG_CONSTANT(T, 64, 7.903662411851774878322e+06),257 BOOST_MATH_BIG_CONSTANT(T, 64, -2.622677059040339516093e+07),258 BOOST_MATH_BIG_CONSTANT(T, 64, 5.227776578828667629347e+07),259 BOOST_MATH_BIG_CONSTANT(T, 64, -4.727797957441040896878e+07)260 };261 // LCOV_EXCL_STOP262 return exp(x) * (boost::math::tools::evaluate_polynomial(P, T(1 / x)) + Y) / sqrt(x);263 }264 else if(x < 50)265 {266 // Max error in interpolated form: 1.035e-21267 // Max Error found at float80 precision = Poly: 1.885872e-21268 // LCOV_EXCL_START269 BOOST_MATH_STATIC const T Y = 4.011702537536621093750e-01f;270 BOOST_MATH_STATIC const T P[] = {271 BOOST_MATH_BIG_CONSTANT(T, 64, -2.227973351806078464328e-03),272 BOOST_MATH_BIG_CONSTANT(T, 64, 4.986778486088017419036e-02),273 BOOST_MATH_BIG_CONSTANT(T, 64, 2.805066823812285310011e-02),274 BOOST_MATH_BIG_CONSTANT(T, 64, 2.921443721160964964623e-02),275 BOOST_MATH_BIG_CONSTANT(T, 64, 4.517504941996594744052e-02),276 BOOST_MATH_BIG_CONSTANT(T, 64, 6.316922639868793684401e-02),277 BOOST_MATH_BIG_CONSTANT(T, 64, 1.535891099168810015433e+00),278 BOOST_MATH_BIG_CONSTANT(T, 64, -4.706078229522448308087e+01),279 BOOST_MATH_BIG_CONSTANT(T, 64, 1.351015763079160914632e+03),280 BOOST_MATH_BIG_CONSTANT(T, 64, -2.948809013999277355098e+04),281 BOOST_MATH_BIG_CONSTANT(T, 64, 4.967598958582595361757e+05),282 BOOST_MATH_BIG_CONSTANT(T, 64, -6.346924657995383019558e+06),283 BOOST_MATH_BIG_CONSTANT(T, 64, 5.998794574259956613472e+07),284 BOOST_MATH_BIG_CONSTANT(T, 64, -4.016371355801690142095e+08),285 BOOST_MATH_BIG_CONSTANT(T, 64, 1.768791455631826490838e+09),286 BOOST_MATH_BIG_CONSTANT(T, 64, -4.441995678177349895640e+09),287 BOOST_MATH_BIG_CONSTANT(T, 64, 4.482292669974971387738e+09)288 };289 // LCOV_EXCL_STOP290 return exp(x) * (boost::math::tools::evaluate_polynomial(P, T(1 / x)) + Y) / sqrt(x);291 }292 else293 {294 // Bessel I0 over[50, INF]295 // Max error in interpolated form : 5.587e-20296 // Max Error found at float80 precision = Poly : 8.776852e-20297 // LCOV_EXCL_START298 BOOST_MATH_STATIC const T P[] = {299 BOOST_MATH_BIG_CONSTANT(T, 64, 3.98942280401432677955074061e-01),300 BOOST_MATH_BIG_CONSTANT(T, 64, 4.98677850501789875615574058e-02),301 BOOST_MATH_BIG_CONSTANT(T, 64, 2.80506290908675604202206833e-02),302 BOOST_MATH_BIG_CONSTANT(T, 64, 2.92194052159035901631494784e-02),303 BOOST_MATH_BIG_CONSTANT(T, 64, 4.47422430732256364094681137e-02),304 BOOST_MATH_BIG_CONSTANT(T, 64, 9.05971614435738691235525172e-02),305 BOOST_MATH_BIG_CONSTANT(T, 64, 2.29180522595459823234266708e-01),306 BOOST_MATH_BIG_CONSTANT(T, 64, 6.15122547776140254569073131e-01),307 BOOST_MATH_BIG_CONSTANT(T, 64, 7.48491812136365376477357324e+00),308 BOOST_MATH_BIG_CONSTANT(T, 64, -2.45569740166506688169730713e+02),309 BOOST_MATH_BIG_CONSTANT(T, 64, 9.66857566379480730407063170e+03),310 BOOST_MATH_BIG_CONSTANT(T, 64, -2.71924083955641197750323901e+05),311 BOOST_MATH_BIG_CONSTANT(T, 64, 5.74276685704579268845870586e+06),312 BOOST_MATH_BIG_CONSTANT(T, 64, -8.89753803265734681907148778e+07),313 BOOST_MATH_BIG_CONSTANT(T, 64, 9.82590905134996782086242180e+08),314 BOOST_MATH_BIG_CONSTANT(T, 64, -7.30623197145529889358596301e+09),315 BOOST_MATH_BIG_CONSTANT(T, 64, 3.27310000726207055200805893e+10),316 BOOST_MATH_BIG_CONSTANT(T, 64, -6.64365417189215599168817064e+10)317 };318 // LCOV_EXCL_STOP319 T ex = exp(x / 2);320 T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);321 result *= ex;322 return result;323 }324}325 326template <typename T>327BOOST_MATH_GPU_ENABLED T bessel_i0_imp(const T& x, const boost::math::integral_constant<int, 113>&)328{329 BOOST_MATH_STD_USING330 if(x < 7.75)331 {332 // Bessel I0 over[10 ^ -34, 7.75]333 // Max error in interpolated form : 1.274e-34334 // Max Error found at float128 precision = Poly : 3.096091e-34335 // LCOV_EXCL_START336 BOOST_MATH_STATIC const T P[] = {337 BOOST_MATH_BIG_CONSTANT(T, 113, 1.0000000000000000000000000000000001273856e+00),338 BOOST_MATH_BIG_CONSTANT(T, 113, 2.4999999999999999999999999999999107477496e-01),339 BOOST_MATH_BIG_CONSTANT(T, 113, 2.7777777777777777777777777777881795230918e-02),340 BOOST_MATH_BIG_CONSTANT(T, 113, 1.7361111111111111111111111106290091648808e-03),341 BOOST_MATH_BIG_CONSTANT(T, 113, 6.9444444444444444444444445629960334523101e-05),342 BOOST_MATH_BIG_CONSTANT(T, 113, 1.9290123456790123456790105563456483249753e-06),343 BOOST_MATH_BIG_CONSTANT(T, 113, 3.9367598891408415217940836339080514004844e-08),344 BOOST_MATH_BIG_CONSTANT(T, 113, 6.1511873267825648777900014857992724731476e-10),345 BOOST_MATH_BIG_CONSTANT(T, 113, 7.5940584281266233066162999610732449709209e-12),346 BOOST_MATH_BIG_CONSTANT(T, 113, 7.5940584281266232783124723601470051895304e-14),347 BOOST_MATH_BIG_CONSTANT(T, 113, 6.2760813455591936763439337059117957836078e-16),348 BOOST_MATH_BIG_CONSTANT(T, 113, 4.3583898233049738471136482147779094353096e-18),349 BOOST_MATH_BIG_CONSTANT(T, 113, 2.5789288895299965395422423848480340736308e-20),350 BOOST_MATH_BIG_CONSTANT(T, 113, 1.3157800456718804437960453545507623434606e-22),351 BOOST_MATH_BIG_CONSTANT(T, 113, 5.8479113149412360748032684260932041506493e-25),352 BOOST_MATH_BIG_CONSTANT(T, 113, 2.2843403488398038539283241944594140493394e-27),353 BOOST_MATH_BIG_CONSTANT(T, 113, 7.9042925594356556196790242908697582021825e-30),354 BOOST_MATH_BIG_CONSTANT(T, 113, 2.4395919891312152120710245152115597111101e-32),355 BOOST_MATH_BIG_CONSTANT(T, 113, 6.7580986145276689333214547502373003196707e-35),356 BOOST_MATH_BIG_CONSTANT(T, 113, 1.6886514018062348877723837017198859723889e-37),357 BOOST_MATH_BIG_CONSTANT(T, 113, 3.8540558465757554512570197585002702777999e-40),358 BOOST_MATH_BIG_CONSTANT(T, 113, 7.4684706070226893763741850944911705726436e-43),359 BOOST_MATH_BIG_CONSTANT(T, 113, 2.0210715309399646335858150349406935414314e-45)360 };361 // LCOV_EXCL_STOP362 T a = x * x / 4;363 return a * boost::math::tools::evaluate_polynomial(P, a) + 1;364 }365 else if(x < 15)366 {367 // Bessel I0 over[7.75, 15]368 // Max error in interpolated form : 7.534e-35369 // Max Error found at float128 precision = Poly : 6.123912e-34370 // LCOV_EXCL_START371 BOOST_MATH_STATIC const T P[] = {372 BOOST_MATH_BIG_CONSTANT(T, 113, 9.9999999999999999992388573069504617493518e-01),373 BOOST_MATH_BIG_CONSTANT(T, 113, 2.5000000000000000007304739268173096975340e-01),374 BOOST_MATH_BIG_CONSTANT(T, 113, 2.7777777777777777744261405400543564492074e-02),375 BOOST_MATH_BIG_CONSTANT(T, 113, 1.7361111111111111209006987259719750726867e-03),376 BOOST_MATH_BIG_CONSTANT(T, 113, 6.9444444444444442399703186871329381908321e-05),377 BOOST_MATH_BIG_CONSTANT(T, 113, 1.9290123456790126709286741580242189785431e-06),378 BOOST_MATH_BIG_CONSTANT(T, 113, 3.9367598891408374246503061422528266924389e-08),379 BOOST_MATH_BIG_CONSTANT(T, 113, 6.1511873267826068395343047827801353170966e-10),380 BOOST_MATH_BIG_CONSTANT(T, 113, 7.5940584281262673459688011737168286944521e-12),381 BOOST_MATH_BIG_CONSTANT(T, 113, 7.5940584281291583769928563167645746144508e-14),382 BOOST_MATH_BIG_CONSTANT(T, 113, 6.2760813455438840231126529638737436950274e-16),383 BOOST_MATH_BIG_CONSTANT(T, 113, 4.3583898233839583885132809584770578894948e-18),384 BOOST_MATH_BIG_CONSTANT(T, 113, 2.5789288891798658971960571838369339742994e-20),385 BOOST_MATH_BIG_CONSTANT(T, 113, 1.3157800470129311623308216856009970266088e-22),386 BOOST_MATH_BIG_CONSTANT(T, 113, 5.8479112701534604520063520412207286692581e-25),387 BOOST_MATH_BIG_CONSTANT(T, 113, 2.2843404822552330714586265081801727491890e-27),388 BOOST_MATH_BIG_CONSTANT(T, 113, 7.9042888166225242675881424439818162458179e-30),389 BOOST_MATH_BIG_CONSTANT(T, 113, 2.4396027771820721384198604723320045236973e-32),390 BOOST_MATH_BIG_CONSTANT(T, 113, 6.7577659910606076328136207973456511895030e-35),391 BOOST_MATH_BIG_CONSTANT(T, 113, 1.6896548123724136624716224328803899914646e-37),392 BOOST_MATH_BIG_CONSTANT(T, 113, 3.8285850162160539150210466453921758781984e-40),393 BOOST_MATH_BIG_CONSTANT(T, 113, 7.9419071894227736216423562425429524883562e-43),394 BOOST_MATH_BIG_CONSTANT(T, 113, 1.4720374049498608905571855665134539425038e-45),395 BOOST_MATH_BIG_CONSTANT(T, 113, 2.7763533278527958112907118930154738930378e-48),396 BOOST_MATH_BIG_CONSTANT(T, 113, 3.1213839473168678646697528580511702663617e-51),397 BOOST_MATH_BIG_CONSTANT(T, 113, 1.0648035313124146852372607519737686740964e-53),398 -BOOST_MATH_BIG_CONSTANT(T, 113, 5.1255595184052024349371058585102280860878e-57),399 BOOST_MATH_BIG_CONSTANT(T, 113, 3.4652470895944157957727948355523715335882e-59)400 };401 // LCOV_EXCL_STOP402 T a = x * x / 4;403 return a * boost::math::tools::evaluate_polynomial(P, a) + 1;404 }405 else if(x < 30)406 {407 // Max error in interpolated form : 1.808e-34408 // Max Error found at float128 precision = Poly : 2.399403e-34409 // LCOV_EXCL_START410 BOOST_MATH_STATIC const T P[] = {411 BOOST_MATH_BIG_CONSTANT(T, 113, 3.9894228040870793650581242239624530714032e-01),412 BOOST_MATH_BIG_CONSTANT(T, 113, 4.9867780576714783790784348982178607842250e-02),413 BOOST_MATH_BIG_CONSTANT(T, 113, 2.8051948347934462928487999569249907599510e-02),414 BOOST_MATH_BIG_CONSTANT(T, 113, 2.8971143420388958551176254291160976367263e-02),415 BOOST_MATH_BIG_CONSTANT(T, 113, 7.8197359701715582763961322341827341098897e-02),416 BOOST_MATH_BIG_CONSTANT(T, 113, -3.3430484862908317377522273217643346601271e+00),417 BOOST_MATH_BIG_CONSTANT(T, 113, 2.7884507603213662610604413960838990199224e+02),418 BOOST_MATH_BIG_CONSTANT(T, 113, -1.8304926482356755790062999202373909300514e+04),419 BOOST_MATH_BIG_CONSTANT(T, 113, 9.8867173178574875515293357145875120137676e+05),420 BOOST_MATH_BIG_CONSTANT(T, 113, -4.4261178812193528551544261731796888257644e+07),421 BOOST_MATH_BIG_CONSTANT(T, 113, 1.6453010340778116475788083817762403540097e+09),422 BOOST_MATH_BIG_CONSTANT(T, 113, -5.0432401330113978669454035365747869477960e+10),423 BOOST_MATH_BIG_CONSTANT(T, 113, 1.2462165331309799059332310595587606836357e+12),424 BOOST_MATH_BIG_CONSTANT(T, 113, -2.3299800389951335932792950236410844978273e+13),425 BOOST_MATH_BIG_CONSTANT(T, 113, 2.5748218240248714177527965706790413406639e+14),426 BOOST_MATH_BIG_CONSTANT(T, 113, 1.8330014378766930869945511450377736037385e+15),427 BOOST_MATH_BIG_CONSTANT(T, 113, -1.8494610073827453236940544799030787866218e+17),428 BOOST_MATH_BIG_CONSTANT(T, 113, 5.7244661371420647691301043350229977856476e+18),429 BOOST_MATH_BIG_CONSTANT(T, 113, -1.2386378807889388140099109087465781254321e+20),430 BOOST_MATH_BIG_CONSTANT(T, 113, 2.1104000573102013529518477353943384110982e+21),431 BOOST_MATH_BIG_CONSTANT(T, 113, -2.9426541092239879262282594572224300191016e+22),432 BOOST_MATH_BIG_CONSTANT(T, 113, 3.4061439136301913488512592402635688101020e+23),433 BOOST_MATH_BIG_CONSTANT(T, 113, -3.2836554760521986358980180942859101564671e+24),434 BOOST_MATH_BIG_CONSTANT(T, 113, 2.6270285589905206294944214795661236766988e+25),435 BOOST_MATH_BIG_CONSTANT(T, 113, -1.7278631455211972017740134341610659484259e+26),436 BOOST_MATH_BIG_CONSTANT(T, 113, 9.1971734473772196124736986948034978906801e+26),437 BOOST_MATH_BIG_CONSTANT(T, 113, -3.8669270707172568763908838463689093500098e+27),438 BOOST_MATH_BIG_CONSTANT(T, 113, 1.2368879358870281916900125550129211146626e+28),439 BOOST_MATH_BIG_CONSTANT(T, 113, -2.8296235063297831758204519071113999839858e+28),440 BOOST_MATH_BIG_CONSTANT(T, 113, 4.1253861666023020670144616019148954773662e+28),441 BOOST_MATH_BIG_CONSTANT(T, 113, -2.8809536950051955163648980306847791014734e+28) 442 };443 // LCOV_EXCL_STOP444 return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);445 }446 else if(x < 100)447 {448 // Bessel I0 over[30, 100]449 // Max error in interpolated form : 1.487e-34450 // Max Error found at float128 precision = Poly : 1.929924e-34451 // LCOV_EXCL_START452 BOOST_MATH_STATIC const T P[] = {453 BOOST_MATH_BIG_CONSTANT(T, 113, 3.9894228040143267793996798658172135362278e-01),454 BOOST_MATH_BIG_CONSTANT(T, 113, 4.9867785050179084714910130342157246539820e-02),455 BOOST_MATH_BIG_CONSTANT(T, 113, 2.8050629090725751585266360464766768437048e-02),456 BOOST_MATH_BIG_CONSTANT(T, 113, 2.9219405302833158254515212437025679637597e-02),457 BOOST_MATH_BIG_CONSTANT(T, 113, 4.4742214371598631578107310396249912330627e-02),458 BOOST_MATH_BIG_CONSTANT(T, 113, 9.0602983776478659136184969363625092585520e-02),459 BOOST_MATH_BIG_CONSTANT(T, 113, 2.2839507231977478205885469900971893734770e-01),460 BOOST_MATH_BIG_CONSTANT(T, 113, 6.8925739165733823730525449511456529001868e-01),461 BOOST_MATH_BIG_CONSTANT(T, 113, 2.4238082222874015159424842335385854632223e+00),462 BOOST_MATH_BIG_CONSTANT(T, 113, 9.6759648427182491050716309699208988458050e+00),463 BOOST_MATH_BIG_CONSTANT(T, 113, 4.7292246491169360014875196108746167872215e+01),464 BOOST_MATH_BIG_CONSTANT(T, 113, 3.1001411442786230340015781205680362993575e+01),465 BOOST_MATH_BIG_CONSTANT(T, 113, 9.8277628835804873490331739499978938078848e+03),466 BOOST_MATH_BIG_CONSTANT(T, 113, -3.1208326312801432038715638596517882759639e+05),467 BOOST_MATH_BIG_CONSTANT(T, 113, 9.4813611580683862051838126076298945680803e+06),468 BOOST_MATH_BIG_CONSTANT(T, 113, -2.1278197693321821164135890132925119054391e+08),469 BOOST_MATH_BIG_CONSTANT(T, 113, 3.3190303792682886967459489059860595063574e+09),470 BOOST_MATH_BIG_CONSTANT(T, 113, -2.1580767338646580750893606158043485767644e+10),471 BOOST_MATH_BIG_CONSTANT(T, 113, -5.0256008808415702780816006134784995506549e+11),472 BOOST_MATH_BIG_CONSTANT(T, 113, 1.9044186472918017896554580836514681614475e+13),473 BOOST_MATH_BIG_CONSTANT(T, 113, -3.2521078890073151875661384381880225635135e+14),474 BOOST_MATH_BIG_CONSTANT(T, 113, 3.3620352486836976842181057590770636605454e+15),475 BOOST_MATH_BIG_CONSTANT(T, 113, -2.0375525734060401555856465179734887312420e+16),476 BOOST_MATH_BIG_CONSTANT(T, 113, 5.6392664899881014534361728644608549445131e+16)477 };478 // LCOV_EXCL_STOP479 return exp(x) * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);480 }481 else482 {483 // Bessel I0 over[100, INF]484 // Max error in interpolated form : 5.459e-35485 // Max Error found at float128 precision = Poly : 1.472240e-34486 // LCOV_EXCL_START487 BOOST_MATH_STATIC const T P[] = {488 BOOST_MATH_BIG_CONSTANT(T, 113, 3.9894228040143267793994605993438166526772e-01),489 BOOST_MATH_BIG_CONSTANT(T, 113, 4.9867785050179084742493257495245185241487e-02),490 BOOST_MATH_BIG_CONSTANT(T, 113, 2.8050629090725735167652437695397756897920e-02),491 BOOST_MATH_BIG_CONSTANT(T, 113, 2.9219405302839307466358297347675795965363e-02),492 BOOST_MATH_BIG_CONSTANT(T, 113, 4.4742214369972689474366968442268908028204e-02),493 BOOST_MATH_BIG_CONSTANT(T, 113, 9.0602984099194778006610058410222616383078e-02),494 BOOST_MATH_BIG_CONSTANT(T, 113, 2.2839502241666629677015839125593079416327e-01),495 BOOST_MATH_BIG_CONSTANT(T, 113, 6.8926354981801627920292655818232972385750e-01),496 BOOST_MATH_BIG_CONSTANT(T, 113, 2.4231921590621824187100989532173995000655e+00),497 BOOST_MATH_BIG_CONSTANT(T, 113, 9.7264260959693775207585700654645245723497e+00),498 BOOST_MATH_BIG_CONSTANT(T, 113, 4.3890136225398811195878046856373030127018e+01),499 BOOST_MATH_BIG_CONSTANT(T, 113, 2.1999720924619285464910452647408431234369e+02),500 BOOST_MATH_BIG_CONSTANT(T, 113, 1.2076909538525038580501368530598517194748e+03),501 BOOST_MATH_BIG_CONSTANT(T, 113, 7.5684635141332367730007149159063086133399e+03),502 BOOST_MATH_BIG_CONSTANT(T, 113, 3.5178192543258299267923025833141286569141e+04),503 BOOST_MATH_BIG_CONSTANT(T, 113, 6.2966297919851965784482163987240461837728e+05) 504 };505 // LCOV_EXCL_STOP506 T ex = exp(x / 2);507 T result = ex * boost::math::tools::evaluate_polynomial(P, T(1 / x)) / sqrt(x);508 result *= ex;509 return result;510 }511}512 513template <typename T>514BOOST_MATH_GPU_ENABLED T bessel_i0_imp(const T& x, const boost::math::integral_constant<int, 0>&)515{516 if(boost::math::tools::digits<T>() <= 24)517 return bessel_i0_imp(x, boost::math::integral_constant<int, 24>());518 else if(boost::math::tools::digits<T>() <= 53)519 return bessel_i0_imp(x, boost::math::integral_constant<int, 53>());520 else if(boost::math::tools::digits<T>() <= 64)521 return bessel_i0_imp(x, boost::math::integral_constant<int, 64>());522 else if(boost::math::tools::digits<T>() <= 113)523 return bessel_i0_imp(x, boost::math::integral_constant<int, 113>());524 BOOST_MATH_ASSERT(0);525 return 0;526}527 528template <typename T>529BOOST_MATH_GPU_ENABLED inline T bessel_i0(const T& x)530{531 typedef boost::math::integral_constant<int,532 ((boost::math::numeric_limits<T>::digits == 0) || (boost::math::numeric_limits<T>::radix != 2)) ?533 0 :534 boost::math::numeric_limits<T>::digits <= 24 ?535 24 :536 boost::math::numeric_limits<T>::digits <= 53 ?537 53 :538 boost::math::numeric_limits<T>::digits <= 64 ?539 64 :540 boost::math::numeric_limits<T>::digits <= 113 ?541 113 : -1542 > tag_type;543 544 return bessel_i0_imp(x, tag_type());545}546 547}}} // namespaces548 549#endif // BOOST_MATH_BESSEL_I0_HPP550 551