our PRNG sucks

[riastradh-probcomp]

The Mersenne twister sucks, the seed space we use is tiny, and the /ad hack/ seed management we do makes it even more ridiculous by seeding separate MT instances with sequential integers. All of it, including all uses of boost random and numpy.random, should be replaced by a ChaCha-based PRNG with 256-bit seeds and small states.

Fortunately, most of the work to identify sources of nondeterminism has been done, and some seed parameter is passed in explicitly to every routine that makes random choices, so fixing this is a matter of macheteing your way through the mess you can see, rather than scrutinizing the whole code base to guess where it might be nondeterministic.