std::piecewise_linear_distribution
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piecewise_linear_distribution
(C++11)
std::piecewise_linear_distribution
Member functions
Generation
Characteristics
Non-member functions
(C++11)(C++11)(until C++20)
(C++11)(C++11)
Defined in header
<random>
template< class RealType = double >
class piecewise_linear_distribution;
(since C++11)
class piecewise_linear_distribution;
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 \(\small{[b_i, b_{i+1})}\)[bi, bi+1). The distribution is such that the probability density at each interval boundary is exactly the predefined value \(\small{p_i}\)pi.
bi+1-x
bi+1-bi
+ pi+1 x-bi
bi+1-bi
, where probability densities at interval boundaries \(\small{p_k}\)pk are calculated as \(\small{w_k/S}\)wk/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
(wk+wk+1)(bk+1−bk).
The set of interval boundaries \(\small{b_i}\)bi and the set of weights at boundaries \(\small{w_i}\)wi are the parameters of this distribution.
std::piecewise_linear_distribution satisfies all requirements of RandomNumberDistribution.
Contents
[edit] 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.
[edit] Member types
Member type
Definition
result_type (C++11)
RealType
[edit] Member functions
Generation
Characteristics
[edit] Non-member functions
(C++11)
(function template) [edit]
[edit] Example
Run this code
#include <iomanip> #include <iostream> #include <map> #include <random> #include <string> 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{}; n < 1e4; ++n) ++hist[d(gen)]; for (auto [x, y] : hist) std::cout << std::setw (2) << std::setfill ('0') << x << ' ' << std::string (y / 100, '*') << '\n'; }
Possible output:
00 * 01 *** 02 **** 03 ****** 04 ********* 05 ********* 06 ********* 07 ********** 08 ********* 09 ********** 10 ********* 11 ******* 12 **** 13 *** 14 *