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std::generate_canonical

From cppreference.com
< cpp‎ | numeric‎ | random
 
 
Numerics library
 
Pseudo-random number generation
 
Defined in header <random>
template< class RealType, std::size_t Bits, class Generator >
RealType generate_canonical( Generator& g );
(since C++11)

Generates a random floating point number in range [01).

To generate enough entropy, generate_canonical() will call g() exactly \(\small k\)k times, where \(\small k = \max(1, \lceil \frac{b}{\log_2 R} \rceil)\)k = max(1, ⌈ b / log2 R ⌉) and

[edit] Parameters

g - generator to use to acquire entropy

[edit] Return value

Floating point value in range [01).

[edit] Exceptions

None except from those thrown by g.

[edit] Notes

Some existing implementations have a bug where they may occasionally return 1.0 if RealType is float GCC #63176 LLVM #18767 MSVC STL #1074. This is LWG issue 2524.

[edit] Example

Produce random numbers with 10 bits of randomness: this may produce only k * R distinct values.

Run this code
#include <iostream>
#include <random>
 
int main()
{
 std::random_device rd;
 std::mt19937 gen(rd());
 for (int n = 0; n < 10; ++n)
 std::cout << std::generate_canonical<double, 10>(gen) << ' ';
 std::cout << '\n';
}

Possible output:

0.208143 0.824147 0.0278604 0.343183 0.0173263 0.864057 0.647037 0.539467 0.0583497 0.609219

[edit] See also

produces real values evenly distributed across a range
(class template) [edit]
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