Reproducible use of random_number with a single integer seed

4

Thank you! I think your subroutine will be helpful indeed. I have also found specifying the seed to the RNG inconvenient. Having a robust procedure is great.

As I am writing this, I have another bright idea to boot strap the random_number using itself as shown below to get different integer seeds:

program main
    integer, parameter :: dp = kind(1.0d0)
    integer nseed
    integer, allocatable:: seed(:)
    real(kind=dp), allocatable::  tmp(:)

    call random_seed(size = nseed)
    allocate(seed(nseed))
    allocate(tmp(nseed))

    seed=333331
    call random_seed(put=seed)
    call random_number(tmp) !maybe put this statement in a short do loop
    seed=floor(huge(seed)*tmp)
    call random_seed(put=seed)

    do i=1,5
        call random_number(tmp)
        call random_seed(get=seed)
        print "(100(I12,x))", seed
    enddo

end program main

Hopefully I will get around to doing a small quantitative analysis of effect of seed choice some day :slight_smile: