std::piecewise_linear_distribution
From cppreference.com
Defined in header <random>
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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 [b
i, b
i+1). The distribution is such that the probability density at each interval boundary is exactly the predefined value p
i.
i≤x<b
i+1 is p
i
b i+1-x |
b i+1-b i |
i+1
x-b i |
b i+1-b i |
k are calculated as w
k/S where S is the sum of all
1 |
2 |
k+w
k+1)(b
k+1−b
k).
The set of interval boundaries b
i and the set of weights at boundaries 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.
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Member types
Member type | Definition |
result_type
|
RealType |
param_type
|
the type of the parameter set, see RandomNumberDistribution .
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Member functions
constructs new distribution (public member function) | |
resets the internal state of the distribution (public member function) | |
Generation | |
generates the next random number in the distribution (public member function) | |
Characteristics | |
returns the distribution parameters (public member function) | |
gets or sets the distribution parameter object (public member function) | |
returns the minimum potentially generated value (public member function) | |
returns the maximum potentially generated value (public member function) |
Non-member functions
compares two distribution objects (function) | |
performs stream input and output on pseudo-random number distribution (function template) |
Example
Run this code
#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 *