18> timer:tc(fun fib:main/0). 
    2971215073
    {59352962,ok}                        % 59s… slooow

    19> hipe:c(fib, [o3]).               % compile with Hipe
    {ok,fib}

    20> timer:tc(fun fib:main/0).
    2971215073
    {12570352,ok}                        % 12.5s!

PS that's Erlang, but it will be similar with Elixir.