boost/math
2
0
Fork 0
mirror of https://github.com/boostorg/math.git synced 2026-01-19 16:32:10 +00:00
Code Issues Projects Releases Wiki Activity

Added two more lambert_w examples and requires cxx_numeric_limits

Browse Source
This commit is contained in:
pabristow
2018-10-09 12:53:11 +01:00
parent ea42a834cc
commit 20067e75e5
3 changed files with 24 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
example/lambert_w_precision_example.cpp
View File

@@ -4,7 +4,7 @@
// (See accompanying file LICENSE_1_0.txt or
// copy at http ://www.boost.org/LICENSE_1_0.txt).
//! Lambert W examples of controlling precision
//! Lambert W examples of controlling precision
// #define BOOST_MATH_INSTRUMENT_LAMBERT_W // #define only for (much) diagnostic output.
@@ -76,16 +76,16 @@ int main()
std::cout.precision(std::numeric_limits<cpp_bin_float_50>::digits10);
r = lambert_w0(z); // Default policy.
std::cout << "lambert_w0(z) cpp_bin_float_50 = " << r << std::endl;
std::cout << "lambert_w0(z) cpp_bin_float_50 = " << r << std::endl;
//lambert_w0(z) cpp_bin_float_50 = 1.7455280027406993830743012648753899115352881290809
// [N[productlog[10], 50]] == 1.7455280027406993830743012648753899115352881290809
std::cout.precision(std::numeric_limits<double>::max_digits10);
std::cout << "lambert_w0(z) static_cast from cpp_bin_float_50 = "
<< static_cast<double>(r) << std::endl;
<< static_cast<double>(r) << std::endl;
// double lambert_w0(z) static_cast from cpp_bin_float_50 = 1.7455280027406994
// [N[productlog[10], 17]] == 1.7455280027406994
std::cout << "bits different from Wolfram = "
<< static_cast<int>(float_distance(static_cast<double>(r), 1.7455280027406994))
std::cout << "bits different from Wolfram = "
<< static_cast<int>(float_distance(static_cast<double>(r), 1.7455280027406994))
<< std::endl; // 0
@@ -96,7 +96,7 @@ int main()
std::cout << std::showpoint << std::endl; // and show any significant trailing zeros too.
float x = 10.;
std::cout << "Lambert W (" << x << ") = " << lambert_w0(x) << std::endl;
std::cout << "Lambert W (" << x << ") = " << lambert_w0(x) << std::endl;
//] [/lambert_w_precision_0]
/*
@@ -118,7 +118,7 @@ Lambert W (10.0000000) = 1.74552800
cpp_bin_float_50 w50;
w50 = lambert_w0(z50);
std::cout.precision(std::numeric_limits<cpp_bin_float_50>::max_digits10); // 50 decimal digits.
std::cout << "Reference Lambert W (" << z << ") =\n "
std::cout << "Reference Lambert W (" << z << ") =\n "
<< w50 << std::endl;
std::cout.precision(std::numeric_limits<double>::max_digits10); // 17 decimal digits for double.
double wr = static_cast<double>(w50);
@@ -136,7 +136,7 @@ Lambert W (10.0000000) = 1.74552800
std::cout << "epsilon for float = " << std::numeric_limits<double>::epsilon() << std::endl;
std::cout << "bits different from Halley step = " << static_cast<int>(float_distance(w, ww)) << std::endl;
//] [/lambert_w_precision_1]
/*
//[lambert_w_precision_output_1
@@ -169,7 +169,7 @@ Lambert W (10.0000000) = 1.74552800
cpp_bin_float_50 wm1_50;
wm1_50 = lambert_wm1(z50);
std::cout.precision(std::numeric_limits<cpp_bin_float_50>::max_digits10); // 50 decimal digits.
std::cout << "Reference Lambert W-1 (" << z << ") =\n "
std::cout << "Reference Lambert W-1 (" << z << ") =\n "
<< wm1_50 << std::endl;
std::cout.precision(std::numeric_limits<double>::max_digits10); // 17 decimal digits for double.
double wr = static_cast<double>(wm1_50);
@@ -204,7 +204,7 @@ Lambert W (10.0000000) = 1.74552800
*/
// Similar example using cpp_bin_float_quad (128-bit floating-point types).
cpp_bin_float_quad zq = 10.;
@@ -235,7 +235,7 @@ Lambert W (10.0000000) = 1.74552800
std::cout.precision(std::numeric_limits<cpp_bin_float_quad>::digits10); // 1.745528002740699383074301264875389837
std::cout << "lambert_w0(z) cpp_dec_float_50 cast to quad (digits10(" << std::numeric_limits<cpp_bin_float_quad>::digits10 <<
" ) = " << static_cast<cpp_bin_float_quad>(r) << std::endl; // 1.74552800274069938307430126487539
std::cout.precision(std::numeric_limits<cpp_bin_float_quad>::digits10 + 1); //
std::cout.precision(std::numeric_limits<cpp_bin_float_quad>::digits10 + 1); //
std::cout << "lambert_w0(z) cpp_dec_float_50 cast to quad (digits10(" << std::numeric_limits<cpp_bin_float_quad>::digits10 <<
" ) = " << static_cast<cpp_bin_float_quad>(r) << std::endl; // 1.74552800274069938307430126487539
@@ -259,11 +259,6 @@ Lambert W (10.0000000) = 1.74552800
}
} // int main()
/*
*/