std::piecewise_linear_distribution
Defined in header <random> |
||
---|---|---|
template< class RealType = double > class piecewise_linear_distribution; |
(since C++11) |
std::piecewise_linear_distribution
produces random floating-point numbers, which are distributed according to a linear probability density function within each of the several subintervals \(\small{[b_i, b_{i+1})}\)[b
i, b
i+1). The distribution is such that the probability density at each interval boundary is exactly the predefined value \(\small{p_i}\)p
i. The probability density for any \(\small{ b_i \le x < b_{i+1} }\)b.
i≤x<b
i+1 is \(\small{p_i\frac{b_{i+1}-x}{b_{i+1}-b_i} + p_{i+1}\frac{x-b_i}{b_{i+1}-b_i} }\) bi+1-x/bi+1-bi + x-bi/bi+1-bi , where probability densities at interval boundaries \(\small{p_k}\)p
k are calculated as \(\small{w_k/S}\)w
k/S where \(\small{S}\)S is the sum of all \(\small{\frac{1}{2}(w_k + w_{k+1})(b_{k+1} - b_k)}\) 1/2(w
k+w
k+1)(b
k+1−b
k).
The set of interval boundaries \(\small{b_i}\)b
i and the set of weights at boundaries \(\small{w_i}\)w
i are the parameters of this distribution.
std::piecewise_linear_distribution
satisfies all requirements of RandomNumberDistribution.
Template parameters
RealType | - | The result type generated by the generator. The effect is undefined if this is not one of float , double , or long double . |
Member types
Member type | Definition |
---|---|
result_type (C++11) |
RealType |
param_type (C++11) |
the type of the parameter set, see RandomNumberDistribution. |
Member functions
(C++11)
|
constructs new distribution (public member function) |
(C++11)
|
resets the internal state of the distribution (public member function) |
Generation |
|
(C++11)
|
generates the next random number in the distribution (public member function) |
Characteristics |
|
returns the distribution parameters (public member function) |
|
(C++11)
|
gets or sets the distribution parameter object (public member function) |
(C++11)
|
returns the minimum potentially generated value (public member function) |
(C++11)
|
returns the maximum potentially generated value (public member function) |
Non-member functions
(C++11)(C++11)(removed in C++20)
|
compares two distribution objects (function) |
(C++11)
|
performs stream input and output on pseudo-random number distribution (function template) |
Example
#include <iostream> #include <iomanip> #include <string> #include <map> #include <random> int main() { std::random_device rd; std::mt19937 gen(rd()); // increase the probability from 0 to 5 // remain flat from 5 to 10 // decrease from 10 to 15 at the same rate std::vector<double> i{0, 5, 10, 15}; std::vector<double> w{0, 1, 1, 0}; std::piecewise_linear_distribution<> d(i.begin(), i.end(), w.begin()); std::map<int, int> hist; for(int n=0; n<10000; ++n) { ++hist[d(gen)]; } for(auto p : hist) { std::cout << std::setw(2) << std::setfill('0') << p.first << ' ' << std::string(p.second/100,'*') << '\n'; } }
Possible output:
00 * 01 *** 02 **** 03 ****** 04 ********* 05 ********* 06 ********* 07 ********** 08 ********* 09 ********** 10 ********* 11 ******* 12 **** 13 *** 14 *
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