ceph/src/boost/libs/multiprecision/plots/cpp_bin_float_erf_errors.cpp

   1
   2 //  (C) Copyright Nick Thompson 2020.
   3 //  (C) Copyright John Maddock 2020.
   4 //  Use, modification and distribution are subject to the
   5 //  Boost Software License, Version 1.0. (See accompanying file
   6 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 #include <iostream>
   8 #include <boost/math/tools/ulps_plot.hpp>
   9 #include <boost/core/demangle.hpp>
  10 #include <boost/multiprecision/mpfr.hpp>
  11 #include <boost/multiprecision/cpp_bin_float.hpp>
  12
  13 using boost::math::tools::ulps_plot;
  14
  15 int main() {
  16    using PreciseReal = boost::multiprecision::mpfr_float_100;
  17    using CoarseReal = boost::multiprecision::cpp_bin_float_50;
  18
  19    typedef boost::math::policies::policy<
  20       boost::math::policies::promote_float<false>,
  21       boost::math::policies::promote_double<false> >
  22       no_promote_policy;
  23
  24    auto ai_coarse = [](CoarseReal const& x)->CoarseReal {
  25       return erf(x);
  26    };
  27    auto ai_precise = [](PreciseReal const& x)->PreciseReal {
  28       return erf(x);
  29    };
  30
  31    std::string filename = "cpp_bin_float_erf.svg";
  32    int samples = 100000;
  33    // How many pixels wide do you want your .svg?
  34    int width = 700;
  35    // Near a root, we have unbounded relative error. So for functions with roots, we define an ULP clip:
  36    PreciseReal clip = 40;
  37    // Should we perturb the abscissas?
  38    bool perturb_abscissas = false;
  39    auto plot = ulps_plot<decltype(ai_precise), PreciseReal, CoarseReal>(ai_precise, CoarseReal(-10), CoarseReal(10), samples, perturb_abscissas);
  40    // Note the argument chaining:
  41    plot.clip(clip).width(width);
  42    plot.background_color("white").font_color("black");
  43    // Sometimes it's useful to set a title, but in many cases it's more useful to just use a caption.
  44    //std::string title = "Airy Ai ULP plot at " + boost::core::demangle(typeid(CoarseReal).name()) + " precision";
  45    //plot.title(title);
  46    plot.vertical_lines(6);
  47    plot.add_fn(ai_coarse);
  48    // You can write the plot to a stream:
  49    //std::cout << plot;
  50    // Or to a file:
  51    plot.write(filename);
  52 }