[Discuss-gnuradio] RFC: change gr::random from boost::mt19937 to gnuradio/xoroshiro128p.h

[CEL]

Hi folks,

we do not often get the chance to break API; releases like 3.8 are such
opportunities.

Not so long ago, we (I think it was Stefan, in fact) replaced a bad
random generator with boost::mt19937 (a Mersenne Twister implementation
with both known sufficient statistical properties and known bad speed).

After that, we had to fix fastnoise_source and other blocks (mainly,
because they were using non-threadsafe libc functions at runtime) by
introducing our own implementation of XOROSHIRO128+¹.

Should we be switching out the generator in gr::random to use that?

Pro:

+ Way, way faster
+ Getting rid of yet another boost thing²
+ Consolidation of RNGs used
+ Being in control of the RNG allows us to keep it's API stable for as
long as we want³

Contra:

- API change
- Code change that's not 100% necessary

What do you think?

Best regards,
Marcus

¹ That's a relatively well-tested algorithm with high speed, low memory
footprint, and in our implementation, isolated state. It's statistical
properties are good to very good, but it's not been in as broad use as
MT19937. I don't think we'll find bugs in it (I've run a good amount of
statistical analysis on it).
² That exact RNG was a source of trouble before – somewhere around
1.48, IIRC, Boost decided to move its namespace without warning or
documentation. That's the main anecdote why I'm weary of Boost.
³ Python 2->3 changed semantics for a couple of random generators, and
some of that broke GR code, which is why I'm interested in having
control over our RNG.