std::piecewise_constant_distribution
Defined in header <random> |
||
|---|---|---|
template< class RealType = double > class piecewise_constant_distribution; |
(since C++11) |
std::piecewise_constant_distribution produces random floating-point numbers, which are uniformly distributed within each of the several subintervals [b
i, b
i+1), each with its own weight w
i. The set of interval boundaries and the set of weights are the parameters of this distribution. The probability density for any b.
i≤x<b
i+1 is wi / S (bi+1 - bi) . where S is the sum of all weights.
std::piecewise_constant_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 |
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 <string>
#include <map>
#include <random>
int main()
{
std::random_device rd;
std::mt19937 gen(rd());
// 50% of the time, generate a random number between 0 and 1
// 50% of the time, generate a random number between 10 and 15
std::vector<double> i{0, 1, 10, 15};
std::vector<double> w{ 1, 0, 1 };
std::piecewise_constant_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::hex << std::uppercase << p.first << ' '
<< std::string(p.second/100, '*') << '\n';
}
}
Possible output:
0 ************************************************** A ********** B ********* C ********* D ********** E *********
References
- C++20 standard (ISO/IEC 14882:2020):
- 29.6.9.6.2 Class template piecewise_constant_distribution [rand.dist.samp.pconst] (p: 1207-1208)
- C++17 standard (ISO/IEC 14882:2017):
- 29.6.8.6.2 Class template piecewise_constant_distribution [rand.dist.samp.pconst] (p: 1098-1100)
- C++14 standard (ISO/IEC 14882:2014):
- 26.5.8.6.2 Class template piecewise_constant_distribution [rand.dist.samp.pconst] (p: 962-964)
- C++11 standard (ISO/IEC 14882:2011):
- 26.5.8.6.2 Class template piecewise_constant_distribution [rand.dist.samp.pconst] (p: 955-957)
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