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On supported platforms, the random number generator is
xoroshiro128+ generator, as indicated by :random-xoroshiro
being in *features*. This is a Lisp implementation of the
xoroshiro128+ generator by David Blackman and Sebastiano Vigna. See
http://xoroshiro.di.unimi.it for further details.
This generator replaces the MT-19937 generator (see MT-19937 Generator) because it is faster and uses much less memory for the
generator (4 32-bit words). However, the period is shorter.
When CMUCL starts up, *random-state* is initialized by
reading 4 32-bit words from /dev/urandom, when available. If
/dev/urandom is not available, the universal time is used to
initialize *random-state*. The initialization is done is using
splitmix64 with
get-universal-time.
&optional (rng-state *random-state*) ¶Jump the rng-state. This is equivalent to 2^{64} calls to the
xoroshiro128+ generator. It can be used to generate 2^{64}
non-overlapping subsequences for parallel computations.