random_device

This is a header-only drop-in replacement for std::random_device. It requires a POSIX operating system, and the entropy() member function only returns a meaningful value on Linux.

Questions and Answers

Why would I use this code?

According to my tests, this code (using /dev/urandom as a backend) produces random numbers about six times faster than the std::random_device of libstdc++ on my platform (x86_64 Debian). This is achieved by reading from the underlying character device (e.g. /dev/urandom) in bulk.

How do I use this code?

The random_device is in the namespace cout_hello_world. Use it exactly as you would a std::random_device. Furthermore, use the class template cout_hello_world::basic_random_device<std::size_t CallsPerBuffer> to tune the number of calls to operator() which can be made between reads to the underlying character device. The memory used is approximately equal to sizeof(unsigned int) * CallsPerBuffer. cout_hello_world::random_device is defined in the header with

using random_device = basic_random_device<1024>;

How do I integrate this code with my project?

If you’re using a POSIX OS, simply drop the header random_device.hh into your project and go. Be aware that names from POSIX headers (and, on linux, <linux/random.h>) will be placed in the global namespace.