[Caml-list] Threads & the order that module initialization code runs

[Caml-list] Threads & the order that module initialization code runs

[Richard Jones]

A quick question about threads:

I have a few modules simulating a network and some machines connected
to the network.

In, for example, network.ml, I have a bunch of initialization code at
the top level:

--- network.ml ---
let new_queue i =
  (Queue.create (),
   Mutex.create (),
   Condition.create ()) in
let out_queue = Array.init nr_machines new_queue

(* There is one queue of incoming messages to the network thread. *)
let in_queue = Queue.create ()

(* Mutex/condition protecting the in_queue. *)
let in_mutex = Mutex.create ()
let in_cond = Condition.create ()
------

And also I have a Main module which starts up the threads:

--- main.ml ---
(* Create a thread to simulate the network. *)
let network_thread = Thread.create Network.run ();;

(* Start a thread for each of the simulated machines. *)
let machine_thread = Array.init nr_machines (Thread.create Machine.run);;
------

It's obviously going to be a problem if the initialization code in
Network hasn't run by the time the machine threads have been started
up in Main (or if the network thread itself gets started up first).

Now it all seems to work, but am I being lucky or do module
initializers run in some sort of well-defined order I can depend on?

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://freshmeat.net/users/rwmj
Merjis Ltd. http://www.merjis.com/ - all your business data are belong to you.
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in theory?"'

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Re: [Caml-list] Threads & the order that module initialization code runs

[Michel Christophe]

Thanks for answers



Le mar 01/07/2003 à 15:34, Richard Jones a écrit :
> A quick question about threads:
> 
> I have a few modules simulating a network and some machines connected
> to the network.
> 
> In, for example, network.ml, I have a bunch of initialization code at
> the top level:
> 
> --- network.ml ---
> let new_queue i =
>   (Queue.create (),
>    Mutex.create (),
>    Condition.create ()) in
> let out_queue = Array.init nr_machines new_queue
> 
> (* There is one queue of incoming messages to the network thread. *)
> let in_queue = Queue.create ()
> 
> (* Mutex/condition protecting the in_queue. *)
> let in_mutex = Mutex.create ()
> let in_cond = Condition.create ()
> ------
> 
> And also I have a Main module which starts up the threads:
> 
> --- main.ml ---
> (* Create a thread to simulate the network. *)
> let network_thread = Thread.create Network.run ();;
> 
> (* Start a thread for each of the simulated machines. *)
> let machine_thread = Array.init nr_machines (Thread.create Machine.run);;
> ------
> 
> It's obviously going to be a problem if the initialization code in
> Network hasn't run by the time the machine threads have been started
> up in Main (or if the network thread itself gets started up first).
> 
> Now it all seems to work, but am I being lucky or do module
> initializers run in some sort of well-defined order I can depend on?
> 
> Rich.

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Re: [Caml-list] Threads & the order that module initialization code runs

[Yamagata Yoriyuki]

From: Richard Jones <rich@annexia.org>
Subject: [Caml-list] Threads & the order that module initialization code runs
Date: Tue, 1 Jul 2003 14:34:15 +0100

> It's obviously going to be a problem if the initialization code in
> Network hasn't run by the time the machine threads have been started
> up in Main (or if the network thread itself gets started up first).
> 
> Now it all seems to work, but am I being lucky or do module
> initializers run in some sort of well-defined order I can depend on?

The modules are initialized in order of their linking.  You will be
safe if you do
     ocamlc -o program network.cmo ... main.cmo
or 
     ocamlopt -o program network.cmx ... main.cmx

Since you refer Network in Main, the compiler emits an error if
network.cmo is not linked before main.cmo, anyway.

--
Yamagata Yoriyuki

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