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 [b
i, b
i+1). The distribution is such that the probability density at each interval boundary is exactly the predefined value p
i. The probability density for any b.
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. |
Member types
| Member type | Definition |
|---|---|
result_type | RealType |
param_type | the type of the parameter set, see RandomNumberDistribution. |
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
#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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