1 //===----------------------------------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is dual licensed under the MIT and the University of Illinois Open 6 // Source Licenses. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // REQUIRES: long_tests 11 12 // <random> 13 14 // template<class RealType = double> 15 // class piecewise_linear_distribution 16 17 // template<class _URNG> result_type operator()(_URNG& g, const param_type& parm); 18 19 #include <random> 20 #include <vector> 21 #include <iterator> 22 #include <numeric> 23 #include <cassert> 24 25 template <class T> 26 inline 27 T 28 sqr(T x) 29 { 30 return x*x; 31 } 32 33 double 34 f(double x, double a, double m, double b, double c) 35 { 36 return a + m*(sqr(x) - sqr(b))/2 + c*(x-b); 37 } 38 39 int main() 40 { 41 { 42 typedef std::piecewise_linear_distribution<> D; 43 typedef D::param_type P; 44 typedef std::mt19937_64 G; 45 G g; 46 double b[] = {10, 14, 16, 17}; 47 double p[] = {25, 62.5, 12.5, 0}; 48 const size_t Np = sizeof(p) / sizeof(p[0]) - 1; 49 D d; 50 P pa(b, b+Np+1, p); 51 const int N = 1000000; 52 std::vector<D::result_type> u; 53 for (int i = 0; i < N; ++i) 54 { 55 D::result_type v = d(g, pa); 56 assert(10 <= v && v < 17); 57 u.push_back(v); 58 } 59 std::sort(u.begin(), u.end()); 60 int kp = -1; 61 double a; 62 double m; 63 double bk; 64 double c; 65 std::vector<double> areas(Np); 66 double S = 0; 67 for (int i = 0; i < areas.size(); ++i) 68 { 69 areas[i] = (p[i]+p[i+1])*(b[i+1]-b[i])/2; 70 S += areas[i]; 71 } 72 for (int i = 0; i < areas.size(); ++i) 73 areas[i] /= S; 74 for (int i = 0; i < Np+1; ++i) 75 p[i] /= S; 76 for (int i = 0; i < N; ++i) 77 { 78 int k = std::lower_bound(b, b+Np+1, u[i]) - b - 1; 79 if (k != kp) 80 { 81 a = 0; 82 for (int j = 0; j < k; ++j) 83 a += areas[j]; 84 m = (p[k+1] - p[k]) / (b[k+1] - b[k]); 85 bk = b[k]; 86 c = (b[k+1]*p[k] - b[k]*p[k+1]) / (b[k+1] - b[k]); 87 kp = k; 88 } 89 assert(std::abs(f(u[i], a, m, bk, c) - double(i)/N) < .001); 90 } 91 } 92 } 93
