On Fri, 16 Sep 2011 16:08:55 -0400
Alex Rubinsteyn <[email protected]> wrote:
> I ran a very simple experiment gauging the overhead of OCaml's new
> first-class modules.
This is not a valid experiment. In first two cases ocamlopt inlines
function call. Also mind that in this code ocamlopt calls the
Local.f function directly, not through the module.
But let's correctly microbenchmark the cost of direct call vs
indirect vs message sending :)
let n = 100_000_000
let f x = x + 1
let direct () =
let acc = ref 0 in
for i = 0 to n do
acc := !acc + (f 1)
done
module type S = sig val f : int -> int end
module M = struct let f x = x + 1 end
let package = ref (module M : S)
let fstcls () =
let acc = ref 0 in
for i = 0 to n do
let module Local = (val !package : S) in
acc := !acc + (Local.f 1)
done
let o = object method f x = x + 1 end
let obj () =
let acc = ref 0 in
for i = 0 to n do
acc := !acc + o#f 1
done
let () =
match Sys.argv with
| [|_;"direct"|] -> direct ()
| [|_;"fstcls"|] -> fstcls ()
| [|_;"obj"|] -> obj ();
| _ -> failwith "ORLY?"
Disable inlining :
/opt/ocaml-3.12.1/bin/ocamlopt -inline 0 -S speed.ml -o speed
Run (Linux 3.0.0-1-686-pae i686) :
$ time ./speed direct
real 0m0.711s
user 0m0.560s
sys 0m0.012s
$ time ./speed fstcls
real 0m0.631s
user 0m0.508s
sys 0m0.000s
$ time ./speed obj
real 0m1.157s
user 0m0.840s
sys 0m0.016s
Looks like it is time to sprinkle some performance-critical code with first
class modules :)
--
ygrek
http://ygrek.org.ua
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