[erlang-questions] Why is erlc so quick to start?

[Roger Lipscombe]

On 5 January 2015 at 09:14, Vlad Dumitrescu <vladdu55@REDACTED> wrote:
> Hi!
>
> Maybe you can compare "erlc myfile" with "erl -s compile file myfile"? Or
> start some other code that does something relevant, with and without the
> magic arguments.

Given foo.erl:

    -module(foo).
    -export([compile/0]).

    compile() ->
       compile:file("foo.erl"),
       erlang:halt().

"erlc foo.erl" takes 0.18 secs.
"erl -noinput -s foo compile" takes 0.23 secs.
"erl +sbtu +A0 -noinput -mode minimal -boot start_clean -s foo
compile" takes 0.17 secs.

"+sbtu" doesn't seem to make any difference; "+A0" seems to
responsible for ~0.04 secs; "-mode minimal" for ~0.03 secs; "-boot
start_clean", again, seems to make no difference.

With an escript:

    #!/usr/bin/env escript
    %%! +sbtu +A0 -mode minimal -boot start_clean

    main([]) ->
        compile:file("foo.erl").

It takes ~0.17 seconds; without the %%! line, it takes ~0.23 seconds.
These are comparable to the above results.

These results aren't exactly scientifically rigorous. PC spec is as
given in my first email; Erlang is R16B03-1; OS is Linux Mint 17;
methodology was simply to run "/usr/bin/time whatever" at least 5
times and report the number that looked most like the mode.