Unix module troubles & Time functions

Unix module troubles & Time functions

[Julien Michel]

Hi all,
I would like to measure the time a function spends inside a Caml program, for
performance purpose.
I need a function with an accuracy of at least 1us.
I usually use \"gettimeofday\" to achieve this kind of measures with Unix.

So I would like to use the Unix.gettimeofday() function which I expect to have
the same accuracy than the unix one.

I work on an embedded system and I had to specially compile ocamlrun for this
target.

I first tried to compile the sources from my developpement plateform this way:
ocamlc -o main unix.cma *.ml...

then I executed the generated byecode on my embedded target ad got the following
error:
Fatal error: cannot load shared library dllunix
Reason: /usr/local/lib/ocaml/stublibs/dllunix.so: cannot open shared object
file: No such file or directory

whereas, \"dllunix.so\" exists well and the path to raise it is good too!


if I try to compile this way:
ocamlc -o main -cclib -lunix unix.cma *ml
I get the same error as in the message above.


and trying to compile this way:
ocamlc -custom -o main unix.cma *ml
returns this error while executing on my target:
Fatal error: unknown C primitive `unix_dup\'

What can be wrong with my system so that I cannot use the Unix.module?
The Gettimeofday unix function usually works well on my target, is there another
way for having access to it with Caml?

Or generally speaking, does any other function exists to achieve such a
measurement (accuracy about 1 us) ?


Thanks to all

----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.

Re: [Caml-list] Unix module troubles & Time functions

[Jean-Christophe Filliatre]

Julien Michel writes:
 > I would like to measure the time a function spends inside a Caml
 > program, for performance purpose.
 > I need a function with an accuracy of at least 1us.
 > [...]
 > Or generally speaking, does any other function exists to achieve such a
 > measurement (accuracy about 1 us) ?

To do such a measurement, I'm using the Unix.times function, as
follows:

======================================================================
open Unix
  
let utime f x =                                                   
  let u = (times()).tms_utime in                                  
  let y = f x in
  let ut = (times()).tms_utime -. u in
  (y,ut)

let print_utime f x = 
  let (y,ut) = utime f x in
  Printf.printf "user time: %2.2f\n" ut;
  y
======================================================================

Hope this helps,
-- 
Jean-Christophe Filliâtre (http://www.lri.fr/~filliatr)

Re: [Caml-list] Unix module troubles & Time functions

[Julien Michel]

Quoting Jean-Christophe Filliatre <filliatr@lri.fr>:


> To do such a measurement, I'm using the Unix.times function, as
> follows:
>
> ======================================================================
> open Unix
>
> let utime f x =
>   let u = (times()).tms_utime in
>   let y = f x in
>   let ut = (times()).tms_utime -. u in
>   (y,ut)
>
> let print_utime f x =
>   let (y,ut) = utime f x in
>   Printf.printf "user time: %2.2f\n" ut;
>   y
> ======================================================================
>

Thanks for this piece of advice.
Yet, I work on standalone bytcode files, executed with "ocamlrun" on the target.

So I can not use Unix functions just writing "open Unix" and calling some of the
functions it provides us.

The problem remains the same: for the moment I am still not able to use the Unix
module.

Any idea to fix that point?

----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.

Re: [Caml-list] Unix module troubles & Time functions

[William D. Neumann]

On Tue, 18 Jul 2006, Julien Michel wrote:

> and trying to compile this way:
> ocamlc -custom -o main unix.cma *ml
> returns this error while executing on my target:
> Fatal error: unknown C primitive `unix_dup\'
>
> What can be wrong with my system so that I cannot use the Unix.module?

Well, you don't have the dup functionality available.  Possibly other 
things are missing as well.  You cauld look into how the Unix build is 
configured and modify it to skip the functionality you don't have (or 
better yet raise an exception).  But that might be more work than you 
need.

> The Gettimeofday unix function usually works well on my target, is there another
> way for having access to it with Caml?

Yes.  You can write your own interface to the gettimeofday function 
(that's all the Unix module's function is).

timer.c
====================================================================

#include <sys/time.h>
#include <caml/mlvalues.h>
#include <caml/alloc.h>
#include <caml/memory.h>
#include <caml/fail.h>

CAMLprim value my_gettimeofday(value unit)
{
   struct timeval tp;
   if (gettimeofday(&tp, NULL) == -1) caml_failwith("gettimeofday: 
failure");
   return copy_double((double) tp.tv_sec + (double) tp.tv_usec / 1e6);
}

====================================================================

timer.ml
====================================================================

external timeofday : unit -> float = "my_gettimeofday"

let _ =
   let t1 = timeofday ()
   and t2 = Unix.gettimeofday () in
   Printf.printf "mytime: %f, utime: %f\n" t1 t2;;

====================================================================

[414]  9:24AM% ocamlc timer.c 
[415]  9:29AM% ocamlc -custom -o timer.bc timer.o unix.cma timer.ml 
[416]  9:29AM% ./timer.bc 
mytime: 1153236588.033843, utime: 1153236588.033860

(Note, you won't have the Unix module, so you don't need the unix.cma part 
when you compile your use of the new timeofday function, I just neede it 
to compare to the Unix.gettimeofday function)

Read chapter 18 of the OCaml manual for more info on interfacing OCaml 
with C.

William D. Neumann

---

"There's just so many extra children, we could just feed the
children to these tigers.  We don't need them, we're not doing 
anything with them.

Tigers are noble and sleek; children are loud and messy."

         -- Neko Case

Life is unfair.  Kill yourself or get over it.
 	-- Black Box Recorder

Re: [Caml-list] Unix module troubles & Time functions

[Julien Michel]

Thanks a lot William, I am sure it will the best way for having acces to
the Unix Gettimeofday function.
Nevertheless, I used exactly the same code as you gave me below.

While compiling:
ocamlc -c timer.c
no error !
then compiling:
ocamlc -o timer timer.o timer.ml
I get this error:
"Error while linking timer.cmo:
The external function `my_gettimeofday' is not available"

so I tried:
ocamlc -custom -o timer timer.o timer.ml
no error during compilation
but while executing the generated bytecode, wether it is on the development
plateform, or on the embedded target, I get this error:
Fatal error: unknown C primitive `my_gettimeofday'

I am afraid to have came back to the beggining of my problem, with
unixdup...
I do not understand what is going on.
Everthing seems to be ok from the Ocaml side, but there is something wrong
from Unix/system side.

Is there a way so that the runtime system "ocamlrun" can recognize
"my_gettimeofday"?

Do I have to keep the wole content of the original timer.c file, and only
include my_gettimeofday function?


Cheers

----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.