76 lines
2.7 KiB
C++
76 lines
2.7 KiB
C++
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// (C) Copyright Nick Thompson 2020.
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// (C) Copyright John Maddock 2020.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#include <iostream>
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#include <boost/math/tools/ulps_plot.hpp>
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#include <boost/core/demangle.hpp>
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#include <boost/multiprecision/mpfr.hpp>
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#include <boost/multiprecision/cpp_bin_float.hpp>
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#ifdef BOOST_HAS_FLOAT128
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#include <boost/multiprecision/float128.hpp>
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#endif
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using namespace boost::multiprecision;
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#ifndef TEST_TYPE
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#define TEST_TYPE double
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#endif
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std::string test_type_name(BOOST_STRINGIZE(TEST_TYPE));
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std::string test_type_filename(BOOST_STRINGIZE(TEST_TYPE));
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using boost::math::tools::ulps_plot;
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int main()
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{
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std::string::size_type n;
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while ((n = test_type_filename.find_first_not_of("_qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890")) != std::string::npos)
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{
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test_type_filename[n] = '_';
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}
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using PreciseReal = boost::multiprecision::mpfr_float_100;
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using CoarseReal = TEST_TYPE;
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typedef boost::math::policies::policy<
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boost::math::policies::promote_float<false>,
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boost::math::policies::promote_double<false> >
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no_promote_policy;
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auto ai_coarse = [](CoarseReal const& x)->CoarseReal {
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return erf(x);
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};
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auto ai_precise = [](PreciseReal const& x)->PreciseReal {
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return erf(x);
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};
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std::string filename = "erf_errors_";
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filename += test_type_filename;
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filename += ".svg";
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int samples = 100000;
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// How many pixels wide do you want your .svg?
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int width = 700;
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// Near a root, we have unbounded relative error. So for functions with roots, we define an ULP clip:
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PreciseReal clip = 40;
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// Should we perturb the abscissas? i.e., should we compute the high precision function f at x,
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// and the low precision function at the nearest representable x̂ to x?
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// Or should we compute both the high precision and low precision function at a low precision representable x̂?
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bool perturb_abscissas = false;
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auto plot = ulps_plot<decltype(ai_precise), PreciseReal, CoarseReal>(ai_precise, CoarseReal(-10), CoarseReal(10), samples, perturb_abscissas);
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// Note the argument chaining:
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plot.clip(clip).width(width);
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plot.background_color("white").font_color("black");
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// Sometimes it's useful to set a title, but in many cases it's more useful to just use a caption.
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std::string title = "Erf ULP plot at " + test_type_name + " precision";
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plot.title(title);
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plot.vertical_lines(6);
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plot.add_fn(ai_coarse);
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// You can write the plot to a stream:
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//std::cout << plot;
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// Or to a file:
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plot.write(filename);
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}
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