diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 18:24:20 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 18:24:20 +0000 |
commit | 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 (patch) | |
tree | e5d88d25d870d5dedacb6bbdbe2a966086a0a5cf /src/boost/libs/math/example/bessel_zeros_example.cpp | |
parent | Initial commit. (diff) | |
download | ceph-upstream.tar.xz ceph-upstream.zip |
Adding upstream version 14.2.21.upstream/14.2.21upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/boost/libs/math/example/bessel_zeros_example.cpp')
-rw-r--r-- | src/boost/libs/math/example/bessel_zeros_example.cpp | 447 |
1 files changed, 447 insertions, 0 deletions
diff --git a/src/boost/libs/math/example/bessel_zeros_example.cpp b/src/boost/libs/math/example/bessel_zeros_example.cpp new file mode 100644 index 00000000..0d3ec3cc --- /dev/null +++ b/src/boost/libs/math/example/bessel_zeros_example.cpp @@ -0,0 +1,447 @@ +// Copyright Christopher Kormanyos 2013. +// Copyright Paul A. Bristow 2013. +// Copyright John Maddock 2013. + +// Distributed under 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). + +#ifdef _MSC_VER +# pragma warning (disable : 4512) // assignment operator could not be generated. +# pragma warning (disable : 4996) // assignment operator could not be generated. +#endif + +#include <iostream> +#include <limits> +#include <vector> +#include <algorithm> +#include <iomanip> +#include <iterator> + +// Weisstein, Eric W. "Bessel Function Zeros." From MathWorld--A Wolfram Web Resource. +// http://mathworld.wolfram.com/BesselFunctionZeros.html +// Test values can be calculated using [@wolframalpha.com WolframAplha] +// See also http://dlmf.nist.gov/10.21 + +//[bessel_zero_example_1 + +/*`This example demonstrates calculating zeros of the Bessel, Neumann and Airy functions. +It also shows how Boost.Math and Boost.Multiprecision can be combined to provide +a many decimal digit precision. For 50 decimal digit precision we need to include +*/ + + #include <boost/multiprecision/cpp_dec_float.hpp> + +/*`and a `typedef` for `float_type` may be convenient +(allowing a quick switch to re-compute at built-in `double` or other precision) +*/ + typedef boost::multiprecision::cpp_dec_float_50 float_type; + +//`To use the functions for finding zeros of the functions we need + + #include <boost/math/special_functions/bessel.hpp> + +//`This file includes the forward declaration signatures for the zero-finding functions: + +// #include <boost/math/special_functions/math_fwd.hpp> + +/*`but more details are in the full documentation, for example at +[@http://www.boost.org/doc/libs/1_53_0/libs/math/doc/sf_and_dist/html/math_toolkit/special/bessel/bessel_over.html Boost.Math Bessel functions] +*/ + +/*`This example shows obtaining both a single zero of the Bessel function, +and then placing multiple zeros into a container like `std::vector` by providing an iterator. +The signature of the single value function is: + + template <class T> + inline typename detail::bessel_traits<T, T, policies::policy<> >::result_type + cyl_bessel_j_zero(T v, // Floating-point value for Jv. + int m); // start index. + +The result type is controlled by the floating-point type of parameter `v` +(but subject to the usual __precision_policy and __promotion_policy). + +The signature of multiple zeros function is: + + template <class T, class OutputIterator> + inline OutputIterator cyl_bessel_j_zero(T v, // Floating-point value for Jv. + int start_index, // 1-based start index. + unsigned number_of_zeros, + OutputIterator out_it); // iterator into container for zeros. + +There is also a version which allows control of the __policy_section for error handling and precision. + + template <class T, class OutputIterator, class Policy> + inline OutputIterator cyl_bessel_j_zero(T v, // Floating-point value for Jv. + int start_index, // 1-based start index. + unsigned number_of_zeros, + OutputIterator out_it, + const Policy& pol); // iterator into container for zeros. + +*/ +//] [/bessel_zero_example_1] + +//[bessel_zero_example_iterator_1] +/*`We use the `cyl_bessel_j_zero` output iterator parameter `out_it` +to create a sum of 1/zeros[super 2] by defining a custom output iterator: +*/ + +template <class T> +struct output_summation_iterator +{ + output_summation_iterator(T* p) : p_sum(p) + {} + output_summation_iterator& operator*() + { return *this; } + output_summation_iterator& operator++() + { return *this; } + output_summation_iterator& operator++(int) + { return *this; } + output_summation_iterator& operator = (T const& val) + { + *p_sum += 1./ (val * val); // Summing 1/zero^2. + return *this; + } +private: + T* p_sum; +}; + + +//] [/bessel_zero_example_iterator_1] + +int main() +{ + try + { +//[bessel_zero_example_2] + +/*`[tip It is always wise to place code using Boost.Math inside try'n'catch blocks; +this will ensure that helpful error messages can be shown when exceptional conditions arise.] + +First, evaluate a single Bessel zero. + +The precision is controlled by the float-point type of template parameter `T` of `v` +so this example has `double` precision, at least 15 but up to 17 decimal digits (for the common 64-bit double). +*/ + double root = boost::math::cyl_bessel_j_zero(0.0, 1); + // Displaying with default precision of 6 decimal digits: + std::cout << "boost::math::cyl_bessel_j_zero(0.0, 1) " << root << std::endl; // 2.40483 + // And with all the guaranteed (15) digits: + std::cout.precision(std::numeric_limits<double>::digits10); + std::cout << "boost::math::cyl_bessel_j_zero(0.0, 1) " << root << std::endl; // 2.40482555769577 +/*`But note that because the parameter `v` controls the precision of the result, +`v` [*must be a floating-point type]. +So if you provide an integer type, say 0, rather than 0.0, then it will fail to compile thus: +`` + root = boost::math::cyl_bessel_j_zero(0, 1); +`` +with this error message +`` + error C2338: Order must be a floating-point type. +`` + +Optionally, we can use a policy to ignore errors, C-style, returning some value +perhaps infinity or NaN, or the best that can be done. (See __user_error_handling). + +To create a (possibly unwise!) policy that ignores all errors: +*/ + + typedef boost::math::policies::policy + < + boost::math::policies::domain_error<boost::math::policies::ignore_error>, + boost::math::policies::overflow_error<boost::math::policies::ignore_error>, + boost::math::policies::underflow_error<boost::math::policies::ignore_error>, + boost::math::policies::denorm_error<boost::math::policies::ignore_error>, + boost::math::policies::pole_error<boost::math::policies::ignore_error>, + boost::math::policies::evaluation_error<boost::math::policies::ignore_error> + > ignore_all_policy; + + double inf = std::numeric_limits<double>::infinity(); + double nan = std::numeric_limits<double>::quiet_NaN(); + + std::cout << "boost::math::cyl_bessel_j_zero(-1.0, 0) " << std::endl; + double dodgy_root = boost::math::cyl_bessel_j_zero(-1.0, 0, ignore_all_policy()); + std::cout << "boost::math::cyl_bessel_j_zero(-1.0, 1) " << dodgy_root << std::endl; // 1.#QNAN + double inf_root = boost::math::cyl_bessel_j_zero(inf, 1, ignore_all_policy()); + std::cout << "boost::math::cyl_bessel_j_zero(inf, 1) " << inf_root << std::endl; // 1.#QNAN + double nan_root = boost::math::cyl_bessel_j_zero(nan, 1, ignore_all_policy()); + std::cout << "boost::math::cyl_bessel_j_zero(nan, 1) " << nan_root << std::endl; // 1.#QNAN + +/*`Another version of `cyl_bessel_j_zero` allows calculation of multiple zeros with one call, +placing the results in a container, often `std::vector`. +For example, generate five `double` roots of J[sub v] for integral order 2. + +showing the same results as column J[sub 2](x) in table 1 of +[@ http://mathworld.wolfram.com/BesselFunctionZeros.html Wolfram Bessel Function Zeros]. + +*/ + unsigned int n_roots = 5U; + std::vector<double> roots; + boost::math::cyl_bessel_j_zero(2.0, 1, n_roots, std::back_inserter(roots)); + std::copy(roots.begin(), + roots.end(), + std::ostream_iterator<double>(std::cout, "\n")); + +/*`Or generate 50 decimal digit roots of J[sub v] for non-integral order `v = 71/19`. + +We set the precision of the output stream and show trailing zeros to display a fixed 50 decimal digits. +*/ + std::cout.precision(std::numeric_limits<float_type>::digits10); // 50 decimal digits. + std::cout << std::showpoint << std::endl; // Show trailing zeros. + + float_type x = float_type(71) / 19; + float_type r = boost::math::cyl_bessel_j_zero(x, 1); // 1st root. + std::cout << "x = " << x << ", r = " << r << std::endl; + + r = boost::math::cyl_bessel_j_zero(x, 20U); // 20th root. + std::cout << "x = " << x << ", r = " << r << std::endl; + + std::vector<float_type> zeros; + boost::math::cyl_bessel_j_zero(x, 1, 3, std::back_inserter(zeros)); + + std::cout << "cyl_bessel_j_zeros" << std::endl; + // Print the roots to the output stream. + std::copy(zeros.begin(), zeros.end(), + std::ostream_iterator<float_type>(std::cout, "\n")); + +/*`The Neumann function zeros are evaluated very similarly: +*/ + using boost::math::cyl_neumann_zero; + + double zn = cyl_neumann_zero(2., 1); + + std::cout << "cyl_neumann_zero(2., 1) = " << std::endl; + //double zn0 = zn; + // std::cout << "zn0 = " << std::endl; + // std::cout << zn0 << std::endl; + // + std::cout << zn << std::endl; + // std::cout << cyl_neumann_zero(2., 1) << std::endl; + + std::vector<float> nzeros(3); // Space for 3 zeros. + cyl_neumann_zero<float>(2.F, 1, nzeros.size(), nzeros.begin()); + + std::cout << "cyl_neumann_zero<float>(2.F, 1, " << std::endl; + // Print the zeros to the output stream. + std::copy(nzeros.begin(), nzeros.end(), + std::ostream_iterator<float>(std::cout, "\n")); + + std::cout << cyl_neumann_zero(static_cast<float_type>(220)/100, 1) << std::endl; + // 3.6154383428745996706772556069431792744372398748422 + +/*`Finally we show how the output iterator can be used to compute a sum of zeros. + +(See [@https://doi.org/10.1017/S2040618500034067 Ian N. Sneddon, Infinite Sums of Bessel Zeros], +page 150 equation 40). +*/ +//] [/bessel_zero_example_2] + + { +//[bessel_zero_example_iterator_2] +/*`The sum is calculated for many values, converging on the analytical exact value of `1/8`. +*/ + using boost::math::cyl_bessel_j_zero; + double nu = 1.; + double sum = 0; + output_summation_iterator<double> it(&sum); // sum of 1/zeros^2 + cyl_bessel_j_zero(nu, 1, 10000, it); + + double s = 1/(4 * (nu + 1)); // 0.125 = 1/8 is exact analytical solution. + std::cout << std::setprecision(6) << "nu = " << nu << ", sum = " << sum + << ", exact = " << s << std::endl; + // nu = 1.00000, sum = 0.124990, exact = 0.125000 +//] [/bessel_zero_example_iterator_2] + } + } + catch (std::exception& ex) + { + std::cout << "Thrown exception " << ex.what() << std::endl; + } + +//[bessel_zero_example_iterator_3] + +/*`Examples below show effect of 'bad' arguments that throw a `domain_error` exception. +*/ + try + { // Try a negative rank m. + std::cout << "boost::math::cyl_bessel_j_zero(-1.F, -1) " << std::endl; + float dodgy_root = boost::math::cyl_bessel_j_zero(-1.F, -1); + std::cout << "boost::math::cyl_bessel_j_zero(-1.F, -1) " << dodgy_root << std::endl; + // Throw exception Error in function boost::math::cyl_bessel_j_zero<double>(double, int): + // Order argument is -1, but must be >= 0 ! + } + catch (std::exception& ex) + { + std::cout << "Throw exception " << ex.what() << std::endl; + } + +/*`[note The type shown is the type [*after promotion], +using __precision_policy and __promotion_policy, from `float` to `double` in this case.] + +In this example the promotion goes: + +# Arguments are `float` and `int`. +# Treat `int` "as if" it were a `double`, so arguments are `float` and `double`. +# Common type is `double` - so that's the precision we want (and the type that will be returned). +# Evaluate internally as `long double` for full `double` precision. + +See full code for other examples that promote from `double` to `long double`. + +*/ + +//] [/bessel_zero_example_iterator_3] + try + { // order v = inf + std::cout << "boost::math::cyl_bessel_j_zero(infF, 1) " << std::endl; + float infF = std::numeric_limits<float>::infinity(); + float inf_root = boost::math::cyl_bessel_j_zero(infF, 1); + std::cout << "boost::math::cyl_bessel_j_zero(infF, 1) " << inf_root << std::endl; + // boost::math::cyl_bessel_j_zero(-1.F, -1) + //Thrown exception Error in function boost::math::cyl_bessel_j_zero<double>(double, int): + // Requested the -1'th zero, but the rank must be positive ! + } + catch (std::exception& ex) + { + std::cout << "Thrown exception " << ex.what() << std::endl; + } + try + { // order v = inf + double inf = std::numeric_limits<double>::infinity(); + double inf_root = boost::math::cyl_bessel_j_zero(inf, 1); + std::cout << "boost::math::cyl_bessel_j_zero(inf, 1) " << inf_root << std::endl; + // Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, unsigned): + // Order argument is 1.#INF, but must be finite >= 0 ! + } + catch (std::exception& ex) + { + std::cout << "Thrown exception " << ex.what() << std::endl; + } + + try + { // order v = NaN + double nan = std::numeric_limits<double>::quiet_NaN(); + double nan_root = boost::math::cyl_bessel_j_zero(nan, 1); + std::cout << "boost::math::cyl_bessel_j_zero(nan, 1) " << nan_root << std::endl; + // Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, unsigned): + // Order argument is 1.#QNAN, but must be finite >= 0 ! + } + catch (std::exception& ex) + { + std::cout << "Thrown exception " << ex.what() << std::endl; + } + + try + { // Try a negative m. + double dodgy_root = boost::math::cyl_bessel_j_zero(0.0, -1); + // warning C4146: unary minus operator applied to unsigned type, result still unsigned. + std::cout << "boost::math::cyl_bessel_j_zero(0.0, -1) " << dodgy_root << std::endl; + // boost::math::cyl_bessel_j_zero(0.0, -1) 6.74652e+009 + // This *should* fail because m is unreasonably large. + + } + catch (std::exception& ex) + { + std::cout << "Thrown exception " << ex.what() << std::endl; + } + + try + { // m = inf + double inf = std::numeric_limits<double>::infinity(); + double inf_root = boost::math::cyl_bessel_j_zero(0.0, inf); + // warning C4244: 'argument' : conversion from 'double' to 'int', possible loss of data. + std::cout << "boost::math::cyl_bessel_j_zero(0.0, inf) " << inf_root << std::endl; + // Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, int): + // Requested the 0'th zero, but must be > 0 ! + + } + catch (std::exception& ex) + { + std::cout << "Thrown exception " << ex.what() << std::endl; + } + + try + { // m = NaN + std::cout << "boost::math::cyl_bessel_j_zero(0.0, nan) " << std::endl ; + double nan = std::numeric_limits<double>::quiet_NaN(); + double nan_root = boost::math::cyl_bessel_j_zero(0.0, nan); + // warning C4244: 'argument' : conversion from 'double' to 'int', possible loss of data. + std::cout << nan_root << std::endl; + // Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, int): + // Requested the 0'th zero, but must be > 0 ! + } + catch (std::exception& ex) + { + std::cout << "Thrown exception " << ex.what() << std::endl; + } + + } // int main() + +/* +Mathematica: Table[N[BesselJZero[71/19, n], 50], {n, 1, 20, 1}] + +7.2731751938316489503185694262290765588963196701623 +10.724858308883141732536172745851416647110749599085 +14.018504599452388106120459558042660282427471931581 +17.25249845917041718216248716654977734919590383861 +20.456678874044517595180234083894285885460502077814 +23.64363089714234522494551422714731959985405172504 +26.819671140255087745421311470965019261522390519297 +29.988343117423674742679141796661432043878868194142 +33.151796897690520871250862469973445265444791966114 +36.3114160002162074157243540350393860813165201842 +39.468132467505236587945197808083337887765967032029 +42.622597801391236474855034831297954018844433480227 +45.775281464536847753390206207806726581495950012439 +48.926530489173566198367766817478553992471739894799 +52.076607045343002794279746041878924876873478063472 +55.225712944912571393594224327817265689059002890192 +58.374006101538886436775188150439025201735151418932 +61.521611873000965273726742659353136266390944103571 +64.66863105379093036834648221487366079456596628716 +67.815145619696290925556791375555951165111460585458 + +Mathematica: Table[N[BesselKZero[2, n], 50], {n, 1, 5, 1}] +n | +1 | 3.3842417671495934727014260185379031127323883259329 +2 | 6.7938075132682675382911671098369487124493222183854 +3 | 10.023477979360037978505391792081418280789658279097 + + +*/ + + /* +[bessel_zero_output] + + boost::math::cyl_bessel_j_zero(0.0, 1) 2.40483 + boost::math::cyl_bessel_j_zero(0.0, 1) 2.40482555769577 + boost::math::cyl_bessel_j_zero(-1.0, 1) 1.#QNAN + boost::math::cyl_bessel_j_zero(inf, 1) 1.#QNAN + boost::math::cyl_bessel_j_zero(nan, 1) 1.#QNAN + 5.13562230184068 + 8.41724414039986 + 11.6198411721491 + 14.7959517823513 + 17.9598194949878 + + x = 3.7368421052631578947368421052631578947368421052632, r = 7.2731751938316489503185694262290765588963196701623 + x = 3.7368421052631578947368421052631578947368421052632, r = 67.815145619696290925556791375555951165111460585458 + 7.2731751938316489503185694262290765588963196701623 + 10.724858308883141732536172745851416647110749599085 + 14.018504599452388106120459558042660282427471931581 + cyl_neumann_zero(2., 1) = 3.3842417671495935000000000000000000000000000000000 + 3.3842418193817139000000000000000000000000000000000 + 6.7938075065612793000000000000000000000000000000000 + 10.023477554321289000000000000000000000000000000000 + 3.6154383428745996706772556069431792744372398748422 + nu = 1.00000, sum = 0.124990, exact = 0.125000 + Throw exception Error in function boost::math::cyl_bessel_j_zero<double>(double, int): Order argument is -1, but must be >= 0 ! + Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, int): Order argument is 1.#INF, but must be finite >= 0 ! + Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, int): Order argument is 1.#QNAN, but must be finite >= 0 ! + Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, int): Requested the -1'th zero, but must be > 0 ! + Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, int): Requested the -2147483648'th zero, but must be > 0 ! + Throw exception Error in function boost::math::cyl_bessel_j_zero<long double>(long double, int): Requested the -2147483648'th zero, but must be > 0 ! + + +] [/bessel_zero_output] +*/ + |