xoroshiro128+ in Fortran

A Fortran 2008 translation of xoroshiro128+.

Compilation

gfortran -O3 -flto -c m_xoroshiro128plus.f90

The test can then be compiled:

gfortran -O3 -flto test_f90.f90 m_xoroshiro128plus.o -o test_f90

Using gcc 5.3.1, -O3 and -flto are required to inline the code, to get maximum performance.

Usage example

use m_xoroshiro128plus

type(rng_t) :: rng

! Seed the random number generator
call rng%seed((/1337_i8, 31337_i8/))

print *, rng%next() ! A (signed) random 64-bit integer
print *, rng%U01()  ! A double precision [0,1) float

Performance

Generating 1 billion random numbers, using gcc 5.3.1 and -O3 on an i5 6600:

C:       0.87 s
Fortran: 1.07 s

Notes

• You have to seed the random number generator before you use it.
• Because Fortran does not have unsigned integers, the constants have been adjusted to their signed-integer equivalents.