Fortran random seed initialization

September 25, 2021

Fortran 2018 specifies a new subroutine random_init(). Gfortran 9 and Intel oneAPI support random_init.

Build systems such as Meson and CMake can detect compiler capabilities. random/ folder full example

Meson standard random_init detection:

project('foo', ['fortran'])

fc = meson.get_compiler('fortran')

f18random = fc.compiles('''program test
implicit none
intrinsic :: random_init
call random_init(.false., .false.)
end''',
name: 'F2018 random_init')

CMake standard random_init detection:

include(CheckSourceCompiles)

set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
# save link time, only compile is needed

check_source_compiles(Fortran "program test
implicit none
intrinsic :: random_init
call random_init(.false., .false.)
end"
f18random)

Older versions of gfortran call random_seed() gives a unique seed. Not every compiler vendor gives a unique seed for random_seed() however.