1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
|
// (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");
}
|
