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 <algorithm> // for sort 24 #include <cassert> 25 #include <limits> 26 27 template <class T> 28 inline 29 T 30 sqr(T x) 31 { 32 return x*x; 33 } 34 35 double 36 f(double x, double a, double m, double b, double c) 37 { 38 return a + m*(sqr(x) - sqr(b))/2 + c*(x-b); 39 } 40 41 int main() 42 { 43 { 44 typedef std::piecewise_linear_distribution<> D; 45 typedef D::param_type P; 46 typedef std::mt19937_64 G; 47 G g; 48 double b[] = {10, 14, 16, 17}; 49 double p[] = {25, 62.5, 12.5, 0}; 50 const size_t Np = sizeof(p) / sizeof(p[0]) - 1; 51 D d; 52 P pa(b, b+Np+1, p); 53 const size_t N = 1000000; 54 std::vector<D::result_type> u; 55 for (size_t i = 0; i < N; ++i) 56 { 57 D::result_type v = d(g, pa); 58 assert(10 <= v && v < 17); 59 u.push_back(v); 60 } 61 std::sort(u.begin(), u.end()); 62 int kp = -1; 63 double a = std::numeric_limits<double>::quiet_NaN(); 64 double m = std::numeric_limits<double>::quiet_NaN(); 65 double bk = std::numeric_limits<double>::quiet_NaN(); 66 double c = std::numeric_limits<double>::quiet_NaN(); 67 std::vector<double> areas(Np); 68 double S = 0; 69 for (size_t i = 0; i < areas.size(); ++i) 70 { 71 areas[i] = (p[i]+p[i+1])*(b[i+1]-b[i])/2; 72 S += areas[i]; 73 } 74 for (size_t i = 0; i < areas.size(); ++i) 75 areas[i] /= S; 76 for (size_t i = 0; i < Np+1; ++i) 77 p[i] /= S; 78 for (size_t i = 0; i < N; ++i) 79 { 80 int k = std::lower_bound(b, b+Np+1, u[i]) - b - 1; 81 if (k != kp) 82 { 83 a = 0; 84 for (int j = 0; j < k; ++j) 85 a += areas[j]; 86 m = (p[k+1] - p[k]) / (b[k+1] - b[k]); 87 bk = b[k]; 88 c = (b[k+1]*p[k] - b[k]*p[k+1]) / (b[k+1] - b[k]); 89 kp = k; 90 } 91 assert(std::abs(f(u[i], a, m, bk, c) - double(i)/N) < .001); 92 } 93 } 94 } 95
