Execution time of class versus record

[tmp123@menta.net]

Hello,

I've tried to implement two equivalent small programs, the one using
class, the other one using records. The resulting execution times says
that class are 7-8 times slower than record (compiled with ocamlopt in a
Intel machine).

Please, knows someone what I'm doing wrong?

The programs are:

records1.ml
=========
type ra = { mutable t : int }

let main () =
  let a = { t = 0 } in
  for i = 0 to 100000 do
    a.t <- a.t + i
  done;
  Printf.printf "t = %d\n" a.t

let _ =
  let t0 = Unix.gettimeofday () in
  main();
  Printf.printf "elapsed = %f\n" (Unix.gettimeofday() -. t0)

class1.ml
=======
class ca =
  object
    val mutable t = 0

    method add x = t <- t+x
    method get () = t
  end

let main () =
  let a = new ca in
  for i = 0 to 100000 do
    a#add i
  done;
  Printf.printf "t = %d\n" (a#get())

let _ =
  let t0 = Unix.gettimeofday () in
  main();
  Printf.printf "elapsed = %f\n" (Unix.gettimeofday() -. t0)

Thanks a lot.