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 // REQUIRES: long_tests
10
11 // <random>
12
13 // template<class RealType = double>
14 // class piecewise_linear_distribution
15
16 // template<class _URNG> result_type operator()(_URNG& g, const param_type& parm);
17
18 #include <random>
19 #include <vector>
20 #include <iterator>
21 #include <numeric>
22 #include <algorithm> // for sort
23 #include <cassert>
24 #include <limits>
25
26 #include "test_macros.h"
27
28 template <class T>
29 inline
30 T
sqr(T x)31 sqr(T x)
32 {
33 return x*x;
34 }
35
36 double
f(double x,double a,double m,double b,double c)37 f(double x, double a, double m, double b, double c)
38 {
39 return a + m*(sqr(x) - sqr(b))/2 + c*(x-b);
40 }
41
main(int,char **)42 int main(int, char**)
43 {
44 {
45 typedef std::piecewise_linear_distribution<> D;
46 typedef D::param_type P;
47 typedef std::mt19937_64 G;
48 G g;
49 double b[] = {10, 14, 16, 17};
50 double p[] = {25, 62.5, 12.5, 0};
51 const size_t Np = sizeof(p) / sizeof(p[0]) - 1;
52 D d;
53 P pa(b, b+Np+1, p);
54 const size_t N = 1000000;
55 std::vector<D::result_type> u;
56 for (size_t i = 0; i < N; ++i)
57 {
58 D::result_type v = d(g, pa);
59 assert(10 <= v && v < 17);
60 u.push_back(v);
61 }
62 std::sort(u.begin(), u.end());
63 int kp = -1;
64 double a = std::numeric_limits<double>::quiet_NaN();
65 double m = std::numeric_limits<double>::quiet_NaN();
66 double bk = std::numeric_limits<double>::quiet_NaN();
67 double c = std::numeric_limits<double>::quiet_NaN();
68 std::vector<double> areas(Np);
69 double S = 0;
70 for (size_t i = 0; i < areas.size(); ++i)
71 {
72 areas[i] = (p[i]+p[i+1])*(b[i+1]-b[i])/2;
73 S += areas[i];
74 }
75 for (size_t i = 0; i < areas.size(); ++i)
76 areas[i] /= S;
77 for (size_t i = 0; i < Np+1; ++i)
78 p[i] /= S;
79 for (size_t i = 0; i < N; ++i)
80 {
81 int k = std::lower_bound(b, b+Np+1, u[i]) - b - 1;
82 if (k != kp)
83 {
84 a = 0;
85 for (int j = 0; j < k; ++j)
86 a += areas[j];
87 m = (p[k+1] - p[k]) / (b[k+1] - b[k]);
88 bk = b[k];
89 c = (b[k+1]*p[k] - b[k]*p[k+1]) / (b[k+1] - b[k]);
90 kp = k;
91 }
92 assert(std::abs(f(u[i], a, m, bk, c) - double(i)/N) < .001);
93 }
94 }
95
96 return 0;
97 }
98