81 karma · joined November 11, 2014
(And no, I didn't write a Perl script, or have multiple goes to game the score, I just “tried not to do what I thought it'd think I'd do”.)
This is about whether the output of the PRNG passes statistical tests for randomness. In a previous blog post by John D. Cook we saw that it failed the PractRand statistical test suite [1], and now we see that it also fails the older TestU01 suite, too.
When Xorshift128+ and Xoroshiro128+ were launched, they were claimed to be statistically excellent. Those claims have been shown to be false.
[1] https://www.johndcook.com/blog/2017/08/14/testing-rngs-with-...
But a tiny change (XorShift*) is enough to get a generator that passes empirical statistical tests.
The page about other RNGs has lots of good info about this stuff.
The performance graphs show a whole bunch of PCG generators.
You absolutely can predict the Mersenne Twister after 624 outputs (there are several blog posts out there). The Mersenne Twister is also huge (2K of state) and some people claim that as a result it's not cache friendly.
But yes, it's a new thing, so it needs people to look at it.