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 _IntType = int> 12 // class uniform_int_distribution 13 14 // template<class _URNG> result_type operator()(_URNG& g, const param_type& parm); 15 16 #include <random> 17 #include <cassert> 18 #include <cmath> 19 #include <cstddef> 20 #include <numeric> 21 #include <vector> 22 23 #include "test_macros.h" 24 25 template <class T> 26 inline 27 T 28 sqr(T x) 29 { 30 return x * x; 31 } 32 33 int main(int, char**) 34 { 35 { 36 typedef std::uniform_int_distribution<> D; 37 typedef std::minstd_rand G; 38 typedef D::param_type P; 39 G g; 40 D d(5, 100); 41 P p(-10, 20); 42 const int N = 100000; 43 std::vector<D::result_type> u; 44 for (int i = 0; i < N; ++i) 45 { 46 D::result_type v = d(g, p); 47 assert(p.a() <= v && v <= p.b()); 48 u.push_back(v); 49 } 50 double mean = std::accumulate(u.begin(), u.end(), 51 double(0)) / u.size(); 52 double var = 0; 53 double skew = 0; 54 double kurtosis = 0; 55 for (std::size_t i = 0; i < u.size(); ++i) 56 { 57 double dbl = (u[i] - mean); 58 double d2 = sqr(dbl); 59 var += d2; 60 skew += dbl * d2; 61 kurtosis += d2 * d2; 62 } 63 var /= u.size(); 64 double dev = std::sqrt(var); 65 skew /= u.size() * dev * var; 66 kurtosis /= u.size() * var * var; 67 kurtosis -= 3; 68 double x_mean = ((double)p.a() + p.b()) / 2; 69 double x_var = (sqr((double)p.b() - p.a() + 1) - 1) / 12; 70 double x_skew = 0; 71 double x_kurtosis = -6. * (sqr((double)p.b() - p.a() + 1) + 1) / 72 (5. * (sqr((double)p.b() - p.a() + 1) - 1)); 73 assert(std::abs((mean - x_mean) / x_mean) < 0.01); 74 assert(std::abs((var - x_var) / x_var) < 0.01); 75 assert(std::abs(skew - x_skew) < 0.01); 76 assert(std::abs((kurtosis - x_kurtosis) / x_kurtosis) < 0.01); 77 } 78 79 return 0; 80 } 81