std::random_device::entropy
From cppreference.com
< cpp | numeric | random | random device
double entropy() const;
|
(since C++11) | |
Obtains an estimate of the random number device entropy, which is a floating-point value between min() and log
2(max()+1). If the device has n states whose individual probabilities are P
0,...,P
n-1, the device probability S is defined as
S = -Σn-1
i=0P
ilog(P
i)
A deterministic random number generator (e.g. a pseudo-random engine) has entropy zero.
Contents |
[edit] Exceptions
noexcept specification:
noexcept
[edit] Return value
The value of the device entropy, or zero if not applicable.
[edit] Notes
This function is not fully implemented in some standard libraries. For example, gcc and clang always return zero even though the device is non-deterministic. In comparison, Visual C++ always returns 32, and boost.random returns 10.
[edit] Example
Example output on one of the implementations
Run this code
#include <iostream> #include <random> int main() { std::random_device rd; std::cout << rd.entropy() << '\n'; }
Possible output:
32