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124 lines
3.3 KiB
C++
124 lines
3.3 KiB
C++
/*
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* Copyright Nick Thompson, 2019
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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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*/
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#include "math_unit_test.hpp"
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#include <numeric>
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#include <utility>
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#include <random>
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#include <cmath>
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#include <boost/math/tools/test_value.hpp>
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#include <boost/core/demangle.hpp>
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#include <boost/math/tools/agm.hpp>
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#if __has_include(<stdfloat>)
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# include <stdfloat>
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#endif
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#ifdef BOOST_HAS_FLOAT128
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#include <boost/multiprecision/float128.hpp>
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using boost::multiprecision::float128;
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#endif
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using boost::math::tools::agm;
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using std::sqrt;
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template<class Real>
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void test_gauss_constant()
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{
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// http://oeis.org/A014549/constant
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Real G_expected = BOOST_MATH_TEST_VALUE(Real, 0.83462684167407318628142973279904680899399301349034700244982737010368199270952641186969116035127532412906785);
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Real G_computed = 1/agm(sqrt(Real(2)), Real(1));
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if(!CHECK_ULP_CLOSE(G_expected, G_computed, 2)) {
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std::cerr << " Gauss constant not computed correctly.\n";
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}
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}
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template<typename Real>
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void test_scaling()
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{
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Real a = 2;
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Real g = 1;
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Real scale = 7;
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Real expected = agm(scale*a, scale*g);
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Real computed = scale*agm(a, g);
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if(!CHECK_ULP_CLOSE(expected, computed, 2)) {
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std::cerr << " Scaling property agm(kx,ky) = k*agm(x, y) is violated.\n";
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}
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expected = 0;
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computed = agm(a, Real(0));
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if(!CHECK_ULP_CLOSE(expected, computed, 0)) {
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std::cerr << " agm(a, 0) != 0.\n";
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}
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computed = agm(Real(0), Real(0));
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if(!CHECK_ULP_CLOSE(expected, computed, 0)) {
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std::cerr << " agm(0, 0) != 0.\n";
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}
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expected = 1;
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computed = agm(Real(1), Real(1));
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if(!CHECK_ULP_CLOSE(expected, computed, 0)) {
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std::cerr << " agm(1, 1) != 1.\n";
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}
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expected = 7;
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computed = agm(Real(7), Real(7));
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if(!CHECK_ULP_CLOSE(expected, computed, 0)) {
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std::cerr << " agm(7, 7) != 1.\n";
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}
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// Properties I found at: https://mathworld.wolfram.com/Arithmetic-GeometricMean.html
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// agm(x,y) = agm((x+y)/2, sqrt(xy))
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expected = agm(Real(3), Real(1));
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computed = agm(Real(2), sqrt(Real(3)));
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if(!CHECK_ULP_CLOSE(expected, computed, 0)) {
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std::cerr << " agm(x, y) != agm((x+y)/2, sqrt(xy)).\n";
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}
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//computed = agm(std::numeric_limits<Real>::infinity(), Real(7));
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//std::cout << "Computed at infinity = " << computed << "\n";
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for (Real x = 0; x < 1; x += Real(1)/128) {
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expected = agm(Real(1), sqrt(1-x*x));
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computed = agm(1+x, 1-x);
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if(!CHECK_ULP_CLOSE(expected, computed, 0)) {
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std::cerr << " agm(1, sqrt(1-x^2) != agm(1+x,1-x).\n";
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}
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}
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}
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int main()
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{
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#ifdef __STDCPP_FLOAT32_T__
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test_gauss_constant<std::float32_t>();
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test_scaling<std::float32_t>();
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#else
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test_gauss_constant<float>();
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test_scaling<float>();
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#endif
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#ifdef __STDCPP_FLOAT64_T__
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test_scaling<std::float64_t>();
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test_gauss_constant<std::float64_t>();
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#else
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test_scaling<double>();
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test_gauss_constant<double>();
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#endif
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test_scaling<long double>();
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test_gauss_constant<long double>();
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#ifdef BOOST_HAS_FLOAT128
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test_gauss_constant<float128>();
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test_scaling<float128>();
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#endif
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return boost::math::test::report_errors();
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}
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