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std::piecewise_linear_distribution

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Pseudo-random number generation
Engines and engine adaptors
Generators
Distributions
Uniform distributions
Bernoulli distributions
Poisson distributions
Normal distributions
Sampling distributions
piecewise_linear_distribution
(C++11)
Seed Sequences
(C++11)
C library
 
 
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
+ p
i+1
x-b
i
b
i+1
-b
i
, where probability densities at interval boundaries p
k
are calculated as w
k
/S
where S is the sum of all
1
2
(w
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.

Contents

Member types

Member type Definition
result_type RealType
param_type the type of the parameter set, unspecified

Member functions

constructs new distribution
(public member function) [edit]
resets the internal state of the distribution
(public member function) [edit]
Generation
generates the next random number in the distribution
(public member function) [edit]
Characteristics
returns the distribution parameters
(public member function) [edit]
gets or sets the distribution parameter object
(public member function) [edit]
returns the minimum potentially generated value
(public member function) [edit]
returns the maximum potentially generated value
(public member function) [edit]

Non-member functions

compares two distribution objects
(function) [edit]
performs stream input and output on pseudo-random number distribution
(function) [edit]

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) << p.first << ' ' << std::string(p.second/100,
    }
}

Output:

0 *
 1 ***
 2 ****
 3 ******
 4 *********
 5 *********
 6 *********
 7 **********
 8 *********
 9 **********
10 *********
11 *******
12 ****
13 ***
14 *