1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 // <random> 10 11 // template<class RealType = double> 12 // class uniform_real_distribution 13 14 // template<class _URNG> result_type operator()(_URNG& g, const param_type& parm); 15 16 #include <random> 17 #include <cassert> 18 #include <vector> 19 #include <numeric> 20 #include <cstddef> 21 22 #include "test_macros.h" 23 24 template <class T> 25 inline 26 T sqr(T x)27sqr(T x) 28 { 29 return x * x; 30 } 31 main(int,char **)32int main(int, char**) 33 { 34 { 35 typedef std::uniform_real_distribution<> D; 36 typedef std::minstd_rand G; 37 typedef D::param_type P; 38 G g; 39 D d(5.5, 25); 40 P p(-10, 20); 41 const int N = 100000; 42 std::vector<D::result_type> u; 43 for (int i = 0; i < N; ++i) 44 { 45 D::result_type v = d(g, p); 46 assert(p.a() <= v && v < p.b()); 47 u.push_back(v); 48 } 49 D::result_type mean = std::accumulate(u.begin(), u.end(), 50 D::result_type(0)) / u.size(); 51 D::result_type var = 0; 52 D::result_type skew = 0; 53 D::result_type kurtosis = 0; 54 for (std::size_t i = 0; i < u.size(); ++i) 55 { 56 D::result_type dbl = (u[i] - mean); 57 D::result_type d2 = sqr(dbl); 58 var += d2; 59 skew += dbl * d2; 60 kurtosis += d2 * d2; 61 } 62 var /= u.size(); 63 D::result_type dev = std::sqrt(var); 64 skew /= u.size() * dev * var; 65 kurtosis /= u.size() * var * var; 66 kurtosis -= 3; 67 D::result_type x_mean = (p.a() + p.b()) / 2; 68 D::result_type x_var = sqr(p.b() - p.a()) / 12; 69 D::result_type x_skew = 0; 70 D::result_type x_kurtosis = -6./5; 71 assert(std::abs((mean - x_mean) / x_mean) < 0.01); 72 assert(std::abs((var - x_var) / x_var) < 0.01); 73 assert(std::abs(skew - x_skew) < 0.01); 74 assert(std::abs((kurtosis - x_kurtosis) / x_kurtosis) < 0.01); 75 } 76 77 return 0; 78 } 79