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- // (C) Copyright Raffi Enficiaud 2019.
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- // See http://www.boost.org/libs/test for the library home page.
- //[example_code
- #define BOOST_TEST_MODULE example84
- #include <boost/test/included/unit_test.hpp>
- #include <random>
- #include <cmath>
- // this function does not compute properly the polynomial root estimation
- // in the case of a double root.
- template <class random_generator_t>
- std::pair<double, double> estimate_polynomial_roots(
- random_generator_t& gen,
- std::function<double(double)> polynomial) {
- using namespace std;
- std::uniform_real_distribution<> dis(-10, 10);
- double x1 = dis(gen);
- double x2 = dis(gen);
- double fx1 = polynomial(x1);
- double fx2 = polynomial(x2);
- BOOST_TEST_INFO_SCOPE("sample1 = " << x1);
- BOOST_TEST_INFO_SCOPE("sample2 = " << x2);
- // from Vieta formula
- double minus_b = x2 + x1 - (fx2 - fx1) / (x2 - x1);
- double c = (x1 * fx2 - x2 * fx1 + x2 * x1 * x1 - x1 * x2 * x2) / (x1 - x2);
- BOOST_TEST(minus_b * minus_b >= 4*c);
- return std::make_pair(
- (minus_b - sqrt(minus_b * minus_b - 4 * c)) / 2,
- (minus_b + sqrt(minus_b * minus_b - 4 * c)) / 2);
- }
- BOOST_AUTO_TEST_CASE(quadratic_estimation)
- {
- std::random_device rd;
- unsigned int seed = rd();
- std::mt19937 gen(seed);
- std::uniform_int_distribution<> dis(-10, 10);
- BOOST_TEST_MESSAGE("Seed = " << seed);
- for(int i = 0; i < 50; i++) {
- BOOST_TEST_INFO_SCOPE("trial " << i+1);
- int root1 = dis(gen);
- int root2 = dis(gen);
- if(root1 > root2) {
- std::swap(root1, root2);
- }
- BOOST_TEST_INFO_SCOPE("root1 = " << root1);
- BOOST_TEST_INFO_SCOPE("root2 = " << root2);
- std::pair<double, double> estimated = estimate_polynomial_roots(
- gen,
- [root1, root2](double x) -> double { return (x - root1) * (x - root2); });
- BOOST_TEST(estimated.first == double(root1), 10. % boost::test_tools::tolerance());
- BOOST_TEST(estimated.second == double(root2), 10. % boost::test_tools::tolerance());
- }
- }
- //]
- BOOST_AUTO_TEST_CASE(making_it_fail)
- {
- // cheating a bit ... but shhhh, do not show in the docs ...
- BOOST_FAIL("Making it fail always on all platforms");
- }
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