LICENSE_XOROSHIRO128PLUS

** License for the xoroshiro128plus random number generator **

Written in 2016 by David Blackman and Sebastiano Vigna (vigna@acm.org)
Translated to Fortran 2008 by Jannis Teunissen

To the extent possible under law, the author has dedicated all copyright
and related and neighboring rights to this software to the public domain
worldwide. This software is distributed without any warranty.

See <http://creativecommons.org/publicdomain/zero/1.0/>.

This is the successor to xorshift128+. It is the fastest full-period
generator passing BigCrush without systematic failures, but due to the
relatively short period it is acceptable only for applications with a
mild amount of parallelism; otherwise, use a xorshift1024* generator.

Beside passing BigCrush, this generator passes the PractRand test suite
up to (and included) 16TB, with the exception of binary rank tests,
which fail due to the lowest bit being an LFSR; all other bits pass all
tests. We suggest to use a sign test to extract a random Boolean value.

Note that the generator uses a simulated rotate operation, which most C
compilers will turn into a single instruction. In Java, you can use
Long.rotateLeft(). In languages that do not make low-level rotation
instructions accessible xorshift128+ could be faster.

The state must be seeded so that it is not everywhere zero. If you have
a 64-bit seed, we suggest to seed a splitmix64 generator and use its
output to fill s.