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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
+ 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.

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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http://en.cppreference.com/w/cpp/numeric/random/piecewise_linear_distribution