Get the latest tech news

C++ Seeding Surprises (2015)

Seeding in C++ is stranger than you think.

Quite often, people do a terrible job, supplying low-quality seed data (such as the system time or process id) or combining multiple poor sources in a half-baked way. (Incidentally, these graphs were drawn using an 8-bit incarnation of seed_seq; you'll notice that the second histogram looks identical to its 16-bit counterpart, which lends credence to the idea that we can extrapolate about performance from smaller bit sizes.) A reason to want this property is that the Mersenne Twister and other generators based on linear-feedback shift-register techniques (including XorShift) can't handle an all-zeros state—if you initialize them that way, they'll just output zero forever.

Get the Android app