[erlang-questions] [ANN] xorshift128+ and xorshift64* PRNGs for Erlang

[Kenji Rikitake]

I've released yet another non-cryptographic random number generator
implementations for Erlang. These are still in the alpha phase, so bug
reports and enhancements welcome.

xorshift+ and xorshift* pseudo random number generators (PRNGs) look
promising as faster and more compact alternatives to Mersenne Twister PRNGs
for 64-bit execution environments. Here are the implementations in Erlang
without NIFs, with the MIT license:

xorshift+128 (exsplus)
https://github.com/jj1bdx/exsplus/

xorshift*64 (exs64)
https://github.com/jj1bdx/exs64/

xorshift+128 and xorshift*64 both generate 64-bit integer sequences.

xorshift+128 has two 64-bit integers for the internal state, and the period
is (2^127-1), the same as tinymt-erlang. The execution time of exsplus is
~x1.5 of tinymt-erlang (which generates 32-bit integer sequences) on OTP
17.3 with HiPE on OS X x86_64 and FreeBSD amd64 environments.

xorshift*64 has one 64-bit integer for the internal state, and the period
is (2^64-1). The execution time of exs64 is roughly the same but slightly
faster than exsplus.

Note: the random module algorithm (AS183), designed in 1980s, has only
three 15-bit integers for the internal state, and the period is ~(2^43).

See http://xorshift.di.unimi.it/ for the further details of xorshift+ and
xorshift* algorithms.

Regards,
Kenji Rikitake
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