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Diffstat (limited to 'src/boost/libs/math/example/cstdfloat_example.cpp')
-rw-r--r-- | src/boost/libs/math/example/cstdfloat_example.cpp | 488 |
1 files changed, 488 insertions, 0 deletions
diff --git a/src/boost/libs/math/example/cstdfloat_example.cpp b/src/boost/libs/math/example/cstdfloat_example.cpp new file mode 100644 index 00000000..761e811b --- /dev/null +++ b/src/boost/libs/math/example/cstdfloat_example.cpp @@ -0,0 +1,488 @@ +// Copyright John Maddock 2014 +// Copyright Christopher Kormanyos 2014. +// Copyright Paul A. Bristow 2016. + +// 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) + +// Contains Quickbook snippets as C++ comments - do not remove. + +/* +`This example shows use of a specified-width floating-point typedef +to evaluate a moderately complex math function using +[@http://en.wikipedia.org/wiki/Double-precision_floating-point_format IEEE754 64-bit double-precision]. +about 15 decimal digits `std::numeric_limits<boost::float64_t>::digits10`, +(but never exceeding 17 decimal digits `std::numeric_limits<boost::float64_t>::max_digits10`). + +The Jahnke-Emden lambda function is described at + +Weisstein, Eric W. "Lambda Function." From MathWorld--A Wolfram Web Resource. +http://mathworld.wolfram.com/LambdaFunction.html + +E. Jahnke and F. Emden, "Tables of Functions with Formulae and Curves," +Dover, New York, 4th ed., (1945), pages 180-188. + +*/ + +//[cstdfloat_example_1 +#include <boost/cstdfloat.hpp> // For float_64_t, float128_t. Must be first include! +#include <cmath> // for pow function. +#include <boost/math/special_functions.hpp> // For gamma function. +//] [/cstdfloat_example_1] +#include <boost/type_traits/is_same.hpp> + +#include <iostream> + +/*! +Function max_digits10 +Returns maximum number of possibly significant decimal digits for a floating-point type FPT, +even for older compilers/standard libraries that +lack support for std::numeric_limits<FPT>::max_digits10, +when the Kahan formula 2 + binary_digits * 0.3010 is used instead. +Also provides the correct result for Visual Studio 2010 +(where the value 8 provided for float is wrong). +*/ +namespace boost +{ +template <typename FPT> +const int max_digits10() +{ +// Since max_digits10 is not defined (or wrong) on older systems, define a local max_digits10. + // Usage: int m = max_digits10<boost::float64_t>(); + const int m = +#if (defined BOOST_NO_CXX11_NUMERIC_LIMITS) || (_MSC_VER == 1600) // is wrongly 8 not 9 for VS2010. + 2 + std::numeric_limits<FPT>::digits * 3010/10000; +#else + std::numeric_limits<FPT>::max_digits10; +#endif + return m; +} +} // namespace boost + +//`Define the Jahnke-Emden_lambda function. +//[cstdfloat_example_2 +boost::float64_t jahnke_emden_lambda(boost::float64_t v, boost::float64_t x) +{ + const boost::float64_t gamma_v_plus_one = boost::math::tgamma(v + 1); + const boost::float64_t x_half_pow_v = std::pow(x /2, v); + + return gamma_v_plus_one * boost::math::cyl_bessel_j(x, v) / x_half_pow_v; +} +//] [/cstdfloat_example_2] + +int main() +{ + std::cout.setf(std::ios::showpoint); // show all significant trailing zeros. + + long double p = 1.L; + //std::cout.precision(std::numeric_limits<long double>::digits10); + + std::cout << "pi = " << p << std::endl; + +//[cstdfloat_example_3 +//`Ensure that all possibly significant digits (17) including trailing zeros are shown. + + std::cout.precision(std::numeric_limits<boost::float64_t>::max_digits10); + std::cout.setf(std::ios::showpoint); // Show trailing zeros. + + try + { // Always use try'n'catch blocks to ensure any error messages are displayed. + + // Evaluate and display an evaluation of the Jahnke-Emden lambda function: + boost::float64_t v = 1.; + boost::float64_t x = 1.; + std::cout << jahnke_emden_lambda(v, x) << std::endl; // 0.88010117148986700 +//] [/cstdfloat_example_3] + + // We can show some evaluations with various precisions: + { // float64_t + for (int i = 0; i < 10; i++) + { + std::cout << std::setprecision(2) << boost::float64_t(i) << ' ' + << std::setprecision(std::numeric_limits<boost::float64_t>::max_digits10) + << jahnke_emden_lambda(boost::float64_t(i), v) << std::endl; // + } + } + { // floatmax_t = the maximum available on this platform. + for (int i = 0; i < 10; i++) + { + std::cout << std::setprecision(2) << boost::floatmax_t(i) << ' ' + << std::setprecision(std::numeric_limits<boost::floatmax_t>::max_digits10) + << jahnke_emden_lambda(boost::floatmax_t(i), v) << std::endl; // + } + } + // Show the precision of long double (this might be 64, 80 or 128 bits). + std::cout << "Floating-point type long double is available with:" << std::endl; + std::cout << " std::numeric_limits<long double>::digits10 == " + << std::numeric_limits<long double>::digits10 << std::endl; // 18 + std::cout << " std::numeric_limits<long double>::max_digits10 == " + << std::numeric_limits<long double>::max_digits10 << std::endl; // 21 + long double p = boost::math::constants::pi<double>(); + std::cout.precision(std::numeric_limits<long double>::digits10); + std::cout << "pi = " << p << std::endl; + +//[cstdfloat_constant_2 +//`These allow floating-point [*constants of at least the specified width] to be declared: + + // Declare Archimedes' constant using float32_t with approximately 7 decimal digits of precision. + static const boost::float32_t pi = BOOST_FLOAT32_C(3.1415926536); + + // Declare the Euler-gamma constant with approximately 15 decimal digits of precision. + static const boost::float64_t euler = + BOOST_FLOAT64_C(0.57721566490153286060651209008240243104216); + + // Declare the Golden Ratio constant with the maximum decimal digits of precision that the platform supports. + static const boost::floatmax_t golden_ratio = + BOOST_FLOATMAX_C(1.61803398874989484820458683436563811772); +//] [/cstdfloat_constant_2] + +// http://www.boost.org/doc/libs/1_55_0/libs/multiprecision/doc/html/boost_multiprecision/tut/floats/float128.html +//[cstdfloat_constant_1 +// Display the constant pi to the maximum available precision. + boost::floatmax_t pi_max = boost::math::constants::pi<boost::floatmax_t>(); + std::cout.precision(std::numeric_limits<boost::floatmax_t>::digits10); + std::cout << "Most precise pi = " << pi_max << std::endl; +// If floatmax_t is float_128_t, then +// Most precise pi = 3.141592653589793238462643383279503 +//] [/cstdfloat_constant_1] + +// Test all the floating-point precisions in turn, and if they are available +// then display how many decimal digits of precision. +#ifdef BOOST_FLOAT16_C + std::cout << "Floating-point type boost::float16_t is available." << std::endl; +#else + std::cout << "Floating-point type boost::float16_t is NOT available." << std::endl; +#endif + +#ifdef BOOST_FLOAT32_C + std::cout << "Floating-point type boost::float32_t is available." << std::endl; + std::cout << " std::numeric_limits<boost::float32_t>::digits10 == " + << std::numeric_limits<boost::float32_t>::digits10 << std::endl; + std::cout << " std::numeric_limits<boost::float32_t>::max_digits10 == " + << std::numeric_limits<boost::float32_t>::max_digits10 << std::endl; +#else + std::cout << "Floating-point type boost::float32_t is NOT available." << std::endl; +#endif + +#ifdef BOOST_FLOAT64_C + std::cout << "Floating-point type boost::float64_t is available." << std::endl; + std::cout << " std::numeric_limits<boost::float64_t>::digits10 == " + << std::numeric_limits<boost::float64_t>::digits10 << std::endl; + std::cout << " std::numeric_limits<boost::float64_t>::max_digits10 == " + << std::numeric_limits<boost::float64_t>::max_digits10 << std::endl; +#else + std::cout << "Floating-point type boost::float64_t is NOT available." << std::endl; +#endif + +#ifdef BOOST_FLOAT80_C + std::cout << "Floating-point type boost::float80_t is available." << std::endl; + std::cout << " std::numeric_limits<boost::float80_t>::digits10 == " + << std::numeric_limits<boost::float80_t>::digits10 << std::endl; + std::cout << " std::numeric_limits<boost::float80_t>::max_digits10 == " + << std::numeric_limits<boost::float80_t>::max_digits10 << std::endl; +#else + std::cout << "Floating-point type boost::float80_t is NOT available." << std::endl; +#endif + +#ifdef BOOST_FLOAT128_C + std::cout << "Floating-point type boost::float128_t is available." << std::endl; + std::cout << " std::numeric_limits<boost::float128_t>::digits10 == " + << std::numeric_limits<boost::float128_t>::digits10 << std::endl; + std::cout << " std::numeric_limits<boost::float128_t>::max_digits10 == " + << std::numeric_limits<boost::float128_t>::max_digits10 << std::endl; +#else + std::cout << "Floating-point type boost::float128_t is NOT available." << std::endl; +#endif + +// Show some constants at a precision depending on the available type(s). +#ifdef BOOST_FLOAT16_C + std::cout.precision(boost::max_digits10<boost::float16_t>()); // Show all significant decimal digits, + std::cout.setf(std::ios::showpoint); // including all significant trailing zeros. + + std::cout << "BOOST_FLOAT16_C(123.456789012345678901234567890) = " + << BOOST_FLOAT16_C(123.456789012345678901234567890) << std::endl; + // BOOST_FLOAT16_C(123.456789012345678901234567890) = 123.45678901234568 +#endif + +//[floatmax_widths_1 +#ifdef BOOST_FLOAT32_C + std::cout.precision(boost::max_digits10<boost::float32_t>()); // Show all significant decimal digits, + std::cout.setf(std::ios::showpoint); // including all significant trailing zeros. + std::cout << "BOOST_FLOAT32_C(123.4567890123456789012345678901234567890) = " + << BOOST_FLOAT32_C(123.4567890123456789012345678901234567890) << std::endl; + // BOOST_FLOAT32_C(123.4567890123456789012345678901234567890) = 123.456787 +#endif +//] [/floatmax_widths_1] + +#ifdef BOOST_FLOAT64_C + std::cout.precision(boost::max_digits10<boost::float64_t>()); // Show all significant decimal digits, + std::cout.setf(std::ios::showpoint); // including all significant trailing zeros. + std::cout << "BOOST_FLOAT64_C(123.4567890123456789012345678901234567890) = " + << BOOST_FLOAT64_C(123.4567890123456789012345678901234567890) << std::endl; + // BOOST_FLOAT64_C(123.4567890123456789012345678901234567890) = 123.45678901234568 +#endif + +#ifdef BOOST_FLOAT80_C + std::cout.precision(boost::max_digits10<boost::float80_t>()); // Show all significant decimal digits, + std::cout.setf(std::ios::showpoint); // including all significant trailing zeros. + std::cout << "BOOST_FLOAT80_C(123.4567890123456789012345678901234567890) = " + << BOOST_FLOAT80_C(123.4567890123456789012345678901234567890) << std::endl; + // BOOST_FLOAT80_C(123.4567890123456789012345678901234567890) = 123.456789012345678903 +#endif + +#ifdef BOOST_FLOAT128_C + std::cout.precision(boost::max_digits10<boost::float128_t>()); // Show all significant decimal digits, + std::cout.setf(std::ios::showpoint); // including all significant trailing zeros. + std::cout << "BOOST_FLOAT128_C(123.4567890123456789012345678901234567890) = " + << BOOST_FLOAT128_C(123.4567890123456789012345678901234567890) << std::endl; + // BOOST_FLOAT128_C(123.4567890123456789012345678901234567890) = 123.456789012345678901234567890123453 +#endif + +/* +//[floatmax_widths_2 +BOOST_FLOAT32_C(123.4567890123456789012345678901234567890) = 123.456787 +BOOST_FLOAT64_C(123.4567890123456789012345678901234567890) = 123.45678901234568 +BOOST_FLOAT80_C(123.4567890123456789012345678901234567890) = 123.456789012345678903 +BOOST_FLOAT128_C(123.4567890123456789012345678901234567890) = 123.456789012345678901234567890123453 +//] [/floatmax_widths_2] +*/ + +// Display the precisions available for floatmax_t + +#ifdef BOOST_FLOATMAX_C + BOOST_ASSERT(std::numeric_limits<boost::floatmax_t>::is_specialized == true); + BOOST_ASSERT(std::numeric_limits<boost::floatmax_t>::is_iec559 == true); + BOOST_ASSERT(BOOST_FLOATMAX_C(0.) == 0); + + std::cout << "floatmax_t " << std::numeric_limits<boost::floatmax_t>::digits << " bits\n" // 113 + << std::numeric_limits<boost::floatmax_t>::digits10 << " decimal digits\n" // 34 + << std::numeric_limits<boost::floatmax_t>::max_digits10 << " max_digits\n" // 36 + << std::numeric_limits<boost::floatmax_t>::radix << " radix\n" + << std::endl; + + int significand_bits = std::numeric_limits<boost::floatmax_t>::digits; + int exponent_max = std::numeric_limits<boost::floatmax_t>::max_exponent; + int exponent_min = std::numeric_limits<boost::floatmax_t>::min_exponent; + int exponent_bits = 1 + static_cast<int>(std::log2(std::numeric_limits<boost::floatmax_t>::max_exponent)); + int sign_bits = std::numeric_limits<boost::floatmax_t>::is_signed; + + std::cout << "significand_bits (including one implicit bit)" << significand_bits + << ", exponent_bits " << exponent_bits + << ", sign_bits " << sign_bits << std::endl; + + // One can compute the total number of bits in the floatmax_t, + // but probably not at compile time. + + std::cout << "bits = " << significand_bits + exponent_bits + sign_bits -1 << std::endl; + // -1 to take account of the implicit bit that is not part of the physical layout. + + // One can compare typedefs (but, of course, only those that are defined for the platform in use.) + std::cout.setf(std::ios::boolalpha); + std::cout << "double, double: " << std::is_same<double, double>::value << std::endl; + bool b = boost::is_same<boost::floatmax_t, boost::float64_t>::value; + std::cout << "boost::is_same<boost::floatmax_t, boost::float64_t>::value; " << b << std::endl; + std::cout << "floatmax_t, float64_t: " + << std::is_same<boost::floatmax_t, boost::float64_t>::value << std::endl; + +/*`So the simplest way of obtaining the total number of bits in the floatmax_t +is to infer it from the std::numeric_limits<>::digits value. +This is possible because the type, must be a IEEE754 layout. */ +//[floatmax_1 + const int fpbits = + (std::numeric_limits<boost::floatmax_t>::digits == 113) ? 128 : + (std::numeric_limits<boost::floatmax_t>::digits == 64) ? 80 : + (std::numeric_limits<boost::floatmax_t>::digits == 53) ? 64 : + (std::numeric_limits<boost::floatmax_t>::digits == 24) ? 32 : + (std::numeric_limits<boost::floatmax_t>::digits == 11) ? 16 : + 0; // Unknown - not IEEE754 format. + std::cout << fpbits << " bits." << std::endl; +//] [/floatmax_1] +#endif + + } + catch (std::exception ex) + { // Display details about why any exceptions are thrown. + std::cout << "Thrown exception " << ex.what() << std::endl; + } + +} // int main() + +/* +[cstdfloat_output + +GCC 4.8.1 with quadmath + + pi = 1.00000 + 0.88010117148986700 + 0.0 0.0000000000000000 + 1.0 0.88010117148986700 + 2.0 4.6137984620549872 + 3.0 16.274830009244951 + 4.0 -25.360637961042869 + 5.0 -1257.9038883512264 + 6.0 -12749.592182518225 + 7.0 -3020.9830849309437 + 8.0 2421897.6013183584 + 9.0 45577595.449204877 + 0.0 0.00000000000000000000000000000000000 + 1.0 0.880101171489866995756301548681221902 + 2.0 4.61379846205498722611082484945654869 + 3.0 16.2748300092449511566883302293717861 + 4.0 -25.3606379610428689375112298876047134 + 5.0 -1257.90388835122644195507746189832687 + 6.0 -12749.5921825182249449426308274269104 + 7.0 -3020.98308493094373261556029319763184 + 8.0 2421897.60131835844367742538452148438 + 9.0 45577595.4492048770189285278320312500 + Floating-point type long double is available with: + std::numeric_limits<long double>::digits10 == 18 + std::numeric_limits<long double>::max_digits10 == 21 + pi = 3.14159265358979312 + Most precise pi = 3.141592653589793238462643383279503 + Floating-point type boost::float16_t is NOT available. + Floating-point type boost::float32_t is available. + std::numeric_limits<boost::float32_t>::digits10 == 6 + std::numeric_limits<boost::float32_t>::max_digits10 == 9 + Floating-point type boost::float64_t is available. + std::numeric_limits<boost::float64_t>::digits10 == 15 + std::numeric_limits<boost::float64_t>::max_digits10 == 17 + Floating-point type boost::float80_t is available. + std::numeric_limits<boost::float80_t>::digits10 == 18 + std::numeric_limits<boost::float80_t>::max_digits10 == 21 + Floating-point type boost::float128_t is available. + std::numeric_limits<boost::float128_t>::digits10 == 34 + std::numeric_limits<boost::float128_t>::max_digits10 == 36 + BOOST_FLOAT32_C(123.4567890123456789012345678901234567890) = 123.456787 + BOOST_FLOAT64_C(123.4567890123456789012345678901234567890) = 123.45678901234568 + BOOST_FLOAT80_C(123.4567890123456789012345678901234567890) = 123.456789012345678903 + BOOST_FLOAT128_C(123.4567890123456789012345678901234567890) = 123.456789012345678901234567890123453 + floatmax_t 113 bits + 34 decimal digits + 36 max_digits + 2 radix + + significand_bits (including one implicit bit)113, exponent_bits 15, sign_bits 1 + bits = 128 + double, double: true + boost::is_same<boost::floatmax_t, boost::float64_t>::value; false + floatmax_t, float64_t: false + 128 bits. + + RUN SUCCESSFUL (total time: 53ms) + +GCC 6.1.1 + +pi = 1.00000 +0.88010117148986700 +0.0 0.0000000000000000 +1.0 0.88010117148986700 +2.0 4.6137984620549872 +3.0 16.274830009244951 +4.0 -25.360637961042869 +5.0 -1257.9038883512264 +6.0 -12749.592182518225 +7.0 -3020.9830849309437 +8.0 2421897.6013183584 +9.0 45577595.449204877 +0.0 0.00000000000000000000000000000000000 +1.0 0.880101171489866995756301548681221902 +2.0 4.61379846205498722611082484945654869 +3.0 16.2748300092449511566883302293717861 +4.0 -25.3606379610428689375112298876047134 +5.0 -1257.90388835122644195507746189832687 +6.0 -12749.5921825182249449426308274269104 +7.0 -3020.98308493094373261556029319763184 +8.0 2421897.60131835844367742538452148438 +9.0 45577595.4492048770189285278320312500 +Floating-point type long double is available with: + std::numeric_limits<long double>::digits10 == 18 + std::numeric_limits<long double>::max_digits10 == 21 +pi = 3.14159265358979312 +Most precise pi = 3.14159265358979323846264338327950 +Floating-point type boost::float16_t is NOT available. +Floating-point type boost::float32_t is available. + std::numeric_limits<boost::float32_t>::digits10 == 6 + std::numeric_limits<boost::float32_t>::max_digits10 == 9 +Floating-point type boost::float64_t is available. + std::numeric_limits<boost::float64_t>::digits10 == 15 + std::numeric_limits<boost::float64_t>::max_digits10 == 17 +Floating-point type boost::float80_t is available. + std::numeric_limits<boost::float80_t>::digits10 == 18 + std::numeric_limits<boost::float80_t>::max_digits10 == 21 +Floating-point type boost::float128_t is available. + std::numeric_limits<boost::float128_t>::digits10 == 33 + std::numeric_limits<boost::float128_t>::max_digits10 == 36 +BOOST_FLOAT32_C(123.4567890123456789012345678901234567890) = 123.456787 +BOOST_FLOAT64_C(123.4567890123456789012345678901234567890) = 123.45678901234568 +BOOST_FLOAT80_C(123.4567890123456789012345678901234567890) = 123.456789012345678903 +BOOST_FLOAT128_C(123.4567890123456789012345678901234567890) = 123.456789012345678901234567890123453 +floatmax_t 113 bits +33 decimal digits +36 max_digits +2 radix + +significand_bits (including one implicit bit)113, exponent_bits 15, sign_bits 1 +bits = 128 +double, double: true +boost::is_same<boost::floatmax_t, boost::float64_t>::value; false +floatmax_t, float64_t: false +128 bits. + + + MSVC 2013 64-bit + + 1> pi = 1.00000 + 1> 0.88010117148986700 + 1> 0.00 0.00000000000000000 + 1> 1.0 0.88010117148986700 + 1> 2.0 4.6137984620549854 + 1> 3.0 16.274830009244948 + 1> 4.0 -25.360637961042869 + 1> 5.0 -1257.9038883512258 + 1> 6.0 -12749.592182518225 + 1> 7.0 -3020.9830849309396 + 1> 8.0 2421897.6013183575 + 1> 9.0 45577595.449204892 + 1> 0.00 0.00000000000000000 + 1> 1.0 0.88010117148986700 + 1> 2.0 4.6137984620549854 + 1> 3.0 16.274830009244948 + 1> 4.0 -25.360637961042869 + 1> 5.0 -1257.9038883512258 + 1> 6.0 -12749.592182518225 + 1> 7.0 -3020.9830849309396 + 1> 8.0 2421897.6013183575 + 1> 9.0 45577595.449204892 + 1> Floating-point type long double is available with: + 1> std::numeric_limits<long double>::digits10 == 15 + 1> std::numeric_limits<long double>::max_digits10 == 17 + 1> pi = 3.14159265358979 + 1> Most precise pi = 3.14159265358979 + 1> Floating-point type boost::float16_t is NOT available. + 1> Floating-point type boost::float32_t is available. + 1> std::numeric_limits<boost::float32_t>::digits10 == 6 + 1> std::numeric_limits<boost::float32_t>::max_digits10 == 9 + 1> Floating-point type boost::float64_t is available. + 1> std::numeric_limits<boost::float64_t>::digits10 == 15 + 1> std::numeric_limits<boost::float64_t>::max_digits10 == 17 + 1> Floating-point type boost::float80_t is NOT available. + 1> Floating-point type boost::float128_t is NOT available. + 1> BOOST_FLOAT32_C(123.4567890123456789012345678901234567890) = 123.456787 + 1> BOOST_FLOAT64_C(123.4567890123456789012345678901234567890) = 123.45678901234568 + 1> floatmax_t 53 bits + 1> 15 decimal digits + 1> 17 max_digits + 1> 2 radix + 1> + 1> significand_bits (including one implicit bit)53, exponent_bits 11, sign_bits 1 + 1> bits = 64 + 1> double, double: true + 1> boost::is_same<boost::floatmax_t, boost::float64_t>::value; true + 1> floatmax_t, float64_t: true + 1> 64 bits. +] [/cstdfloat_output] + + +*/ + |