elements function

[jacobwilliams]

Nice paper! FYI: I was experimenting with the elements example. I noticed that it is a good bit faster if you convert fromrv3 from a function to a subroutine. So:

pure subroutine fromrv3(r, v, mu, ele)
    double precision, dimension(:), intent(in) :: r
    double precision, dimension(:), intent(in) :: v
    double precision, intent(in) :: mu
    double precision, dimension(6),intent(out) :: ele
...
end subroutine fromrv3

On my PC with ifort 17.0.2.187 (-O3 flag), for times=1000000, the total/times result goes from about 2.65e-7 to about 1.73e-7.

[helgee]

Thanks, Jacob!

The function version is probably slower since it allocates an additional array on the stack (see here). Do you agree?

Since all other implementations also explicitly return the result and not mutate a parameter like the subroutine version, I prefer to keep the function version.