std::extreme_value_distribution
From cppreference.com
| Defined in header <random>
|
||
template< class RealType = double >
class extreme_value_distribution;
|
(since C++11) | |
Produces random numbers according to the Generalized extreme value distribution (it is also known as Gumbel Type I, log-Weibull, Fisher-Tippett Type I):
- p(x;a,b) =
exp⎛1 b
⎜
⎝
- exp⎛a-x b
⎜
⎝
⎞a-x b
⎟
⎠⎞
⎟
⎠
std::extreme_value_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 (C++11)
|
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 | |
(C++11) |
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
Run this code
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <random>
#include <vector>
template<int Height = 5, int BarWidth = 1, int Padding = 1, int Offset = 0, class Seq>
void draw_vbars(Seq&& s, const bool DrawMinMax = true)
{
static_assert(0 < Height and 0 < BarWidth and 0 <= Padding and 0 <= Offset);
auto cout_n = [](auto&& v, int n = 1)
{
while (n-- > 0)
std::cout << v;
};
const auto [min, max] = std::minmax_element(std::cbegin(s), std::cend(s));
std::vector<std::div_t> qr;
for (typedef decltype(*std::cbegin(s)) V; V e : s)
qr.push_back(std::div(std::lerp(V(0), 8 * Height,
(e - *min) / (*max - *min)), 8));
for (auto h{Height}; h-- > 0; cout_n('\n'))
{
cout_n(' ', Offset);
for (auto dv : qr)
{
const auto q{dv.quot}, r{dv.rem};
unsigned char d[]{0xe2, 0x96, 0x88, 0}; // Full Block: '█'
q < h ? d[0] = ' ', d[1] = 0 : q == h ? d[2] -= (7 - r) : 0;
cout_n(d, BarWidth), cout_n(' ', Padding);
}
if (DrawMinMax && Height > 1)
Height - 1 == h ? std::cout << "┬ " << *max:
h ? std::cout << "│ "
: std::cout << "┴ " << *min;
}
}
int main()
{
std::random_device rd{};
std::mt19937 gen{rd()};
std::extreme_value_distribution<> d{-1.618f, 1.618f};
const int norm = 10'000;
const float cutoff = 0.000'3f;
std::map<int, int> hist{};
for (int n = 0; n != norm; ++n)
++hist[std::round(d(gen))];
std::vector<float> bars;
std::vector<int> indices;
for (const auto& [n, p] : hist)
if (const float x = p * (1.0f / norm); x > cutoff)
{
bars.push_back(x);
indices.push_back(n);
}
draw_vbars<8,4>(bars);
for (int n : indices)
std::cout << ' ' << std::setw(2) << n << " ";
std::cout << '\n';
}
Possible output:
████ ▅▅▅▅ ┬ 0.2186
████ ████ │
▁▁▁▁ ████ ████ ▇▇▇▇ │
████ ████ ████ ████ │
████ ████ ████ ████ ▆▆▆▆ │
████ ████ ████ ████ ████ ▁▁▁▁ │
▄▄▄▄ ████ ████ ████ ████ ████ ████ ▃▃▃▃ │
▁▁▁▁ ████ ████ ████ ████ ████ ████ ████ ████ ▆▆▆▆ ▃▃▃▃ ▂▂▂▂ ▁▁▁▁ ▁▁▁▁ ▁▁▁▁ ▁▁▁▁ ┴ 0.0005
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10