Timeouts in Event module

Timeouts in Event module

[Yaron Minsky]

Does anyone know of a way of achieving timeouts using OCaml's Event
module?  Reppy's Concrrent ML has timeout and attime events which
cover for that need.  I'm wondering if there is some other way of
implementing this using Event, or if this is just a missing feature.

Thanks,
Yaron

Re: [Caml-list] Timeouts in Event module

[SooHyoung Oh]

I implemented a timer library.
Look http://pllab.kaist.ac.kr/~shoh/ocaml/libs/timer/
This library uses Sys module and unix, thread library.


Yaron Minsky 쓴 글:

>Does anyone know of a way of achieving timeouts using OCaml's Event
>module?  Reppy's Concrrent ML has timeout and attime events which
>cover for that need.  I'm wondering if there is some other way of
>implementing this using Event, or if this is just a missing feature.
>
>Thanks,
>Yaron
>
>_______________________________________________
>Caml-list mailing list. Subscription management:
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>Bug reports: http://caml.inria.fr/bin/caml-bugs
>
>  
>

Re: [Caml-list] Timeouts in Event module

[Yaron Minsky]

Thanks.  That looks quite useful.    I suppose one could create a
timed event by creating a channel and scheduling a callback to send on
that channel.  It seems like a bit of a hack (not your library, but
the need to use such a mechanism to simulate timeouts), but it should
do the job.

y


On Mon, 24 Jan 2005 09:53:21 +0900, SooHyoung Oh
<shoh@compiler.kaist.ac.kr> wrote:
> 
> I implemented a timer library.
> Look http://pllab.kaist.ac.kr/~shoh/ocaml/libs/timer/
> This library uses Sys module and unix, thread library.
> 
> Yaron Minsky 쓴 글:
> 
> >Does anyone know of a way of achieving timeouts using OCaml's Event
> >module?  Reppy's Concrrent ML has timeout and attime events which
> >cover for that need.  I'm wondering if there is some other way of
> >implementing this using Event, or if this is just a missing feature.
> >
> >Thanks,
> >Yaron
> >
> >_______________________________________________
> >Caml-list mailing list. Subscription management:
> >http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> >Archives: http://caml.inria.fr
> >Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> >Bug reports: http://caml.inria.fr/bin/caml-bugs
> >
> >
> >
>

Re: [Caml-list] Timeouts in Event module

[Markus Mottl]

On Sun, 23 Jan 2005, Yaron Minsky wrote:
> Thanks.  That looks quite useful.    I suppose one could create a
> timed event by creating a channel and scheduling a callback to send on
> that channel.  It seems like a bit of a hack (not your library, but
> the need to use such a mechanism to simulate timeouts), but it should
> do the job.

I remember having found the following solution, which I use in my projects
now, on the list a while ago:

  let watchdog s v =
    let ch = Event.new_channel () in
    let watchdog_thread () =
      Thread.delay s;
      Event.sync (Event.send ch v) in
    ignore (Thread.create watchdog_thread ());
    Event.receive ch

  let timed_sync s v event = Event.sync (Event.choose [event; watchdog s v])

You can use it e.g. as follows:

  let thread_fun ch =
    (* ... do something long ... *)
    Event.sync (Event.send result) in
  let ch = Event.new_channel () in
  let tid = Thread.create thread_fun ch in
  timed_sync 3.14 default_value (Event.receive ch)

If "thread_fun" doesn't send + synchronize a result within 3.14 seconds
on event channel "ch", then "default_value" will be returned, the result
otherwise.

Regards,
Markus

-- 
Markus Mottl    markus.mottl@gmail.com    http://www.ocaml.info