ceph/src/boost/libs/math/example/agm_example.cpp

   1 //  (C) Copyright Nick Thompson 2020.
   2 //  Use, modification and distribution are subject to the
   3 //  Boost Software License, Version 1.0. (See accompanying file
   4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5 #include <cmath>
   6 #include <iostream>
   7 #include <iomanip>
   8 #include <boost/math/tools/agm.hpp>
   9 #include <boost/math/constants/constants.hpp>
  10
  11 #ifndef BOOST_MATH_STANDALONE
  12 #include <boost/multiprecision/cpp_bin_float.hpp>
  13 #endif
  14
  15 // This example computes the lemniscate constant to high precision using the agm:
  16 using boost::math::tools::agm;
  17 using boost::math::constants::pi;
  18
  19 int main() {
  20     using std::sqrt;
  21
  22     #ifndef BOOST_MATH_STANDALONE
  23     using Real = boost::multiprecision::cpp_bin_float_100;
  24     #else
  25     using Real = long double;
  26     #endif
  27
  28     Real G = agm(sqrt(Real(2)), Real(1));
  29     std::cout << std::setprecision(std::numeric_limits<Real>::max_digits10);
  30     std::cout << " Gauss's lemniscate constant = " << pi<Real>()/G << "\n";
  31     std::cout << "Expected lemniscate constant = " << "2.62205755429211981046483958989111941368275495143162316281682170380079058707041425023029553296142909344613\n";
  32 }