Re: [Newbies] Simple semaphore to synchronize instances of > different classes - Beginners

16 Aug 2012

      Hello Levente, Chris,
As you stated, the problem came from the code executing at UI level
(from workscript).
Forking all the script works very fine !
Thanks very much for your help !
Patrick
2012/8/16, beginners-request@lists.squeakfoundation.org
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Today's Topics:

Re: Simple semaphore to synchronize instances of different
classes (Chris Cunnington)
Re: Re: [Newbies] Simple semaphore to synchronize instances
of	different classes (Levente Uzonyi)
Re: Simple semaphore to synchronize instances of different
classes (Chris Cunningham)

Message: 1
Date: Wed, 15 Aug 2012 16:11:40 -0400
From: Chris Cunnington smalltalktelevision@gmail.com
Subject: Re: [Newbies] Simple semaphore to synchronize instances of
   different	classes
To: "A friendly place to get answers to even the most basic questions
   about	Squeak." beginners@lists.squeakfoundation.org
Message-ID: 502C027C.3040900@gmail.com
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 12-08-15 3:12 PM, patrick dudjalija wrote:
...
|ts sem|
sem:=Semaphore new.
[ts:= TestSynchro new.
ts semaphore:sem.
ts openInWorld.
ts start.] fork.
sem wait.
Transcript cr; show:'Hello world !';cr.
Well, I can observer a few things. The first is that running this code
in a Workspace the tem vars are unnecessary. (ie. |ts sem|). The second
thing is that if I execute the code down to "fork" it runs fine. A blue
square appears in the corner and it counts steps one to nine in the
Transcript. It's only when you add "sem wait" that it freezes. I had to
use Command+. on my Mac to unfreeze it. And I'm not convinced this is a
bug. Remember, I don't think there is a Morph anywhere that uses
Semaphore in #step. I have a feeling this is not a bug and that it's
doing exactly what it's supposed to. You have created a Morph and now
you've stopped it with #wait. I bet that's locking up the entire World,
so it appears to freeze. That's my guess.
HTH,
Chris

Message: 2
Date: Wed, 15 Aug 2012 23:03:27 +0200 (CEST)
From: Levente Uzonyi leves@elte.hu
Subject: Re: Re: [Newbies] Simple semaphore to synchronize instances
   of	different classes
To: "A friendly place to get answers to even the most basic questions
   about	Squeak." beginners@lists.squeakfoundation.org
Message-ID:
   alpine.DEB.2.00.1208152300240.15054@login01.caesar.elte.hu
Content-Type: text/plain; charset="iso-8859-1"
On Wed, 15 Aug 2012, patrick dudjalija wrote:
...
Sorry, i've sent an unfinished mail  ...
Second try :
The problem : synchronizing an instance of a class gameEngine which starts
instances of classes which implement transition screen / game levels.
Pseudo-level code :
Game engine

start introscreen- wait semaphore

-start level 1

wait semaphore
start level 2

-wait semaphore

start finished screen

See example of code in Squeak with semaphore in my previous mails.
I wonder why the code is freezing.
If you evaluate something in a workspace, it will be executed by the UI
process. If you wait for something, then the whole UI will stop responding
while you're waiting.
Btw, I don't think Semaphores are the thing you're looking for. Semaphores
are for synchronizing processes, but AFAIK Morphic is a single process
framework.
Levente
...
Thanks for any help.
Patrick Dudjalija
2012/8/15 patrick dudjalija patrick.dudjalija@gmail.com
      Hello Chris !
Thank you for the link. Free books of Stephane Ducasse are inderdeed a
*MUST*.
http://stephane.ducasse.free.fr/FreeBooks.html
(BTW, everybody should consider a little donation to support him)
I'm realizing that my question is unclear.
Let me have a new try in pseudocode.
The problem : synchronizing an instance of a class gameEngine which starts
instances of transition screen / game levels.
Game engine
2012/8/15 beginners-request@lists.squeakfoundation.org
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  Today's Topics:

     1. Simple semaphore to synchronize instances of different
        classes (patrick dudjalija)
     2. Re: Simple semaphore to synchronize instances of different
        classes (Chris Cunnington)

  Message: 1
  Date: Tue, 14 Aug 2012 21:24:06 +0200
  From: patrick dudjalija <patrick.dudjalija@gmail.com>
  Subject: [Newbies] Simple semaphore to synchronize instances of
          different       classes
  To: beginners <beginners@lists.squeakfoundation.org>
  Message-ID:

CAEMqm6GttreSY5i+SA=Hg1=C8sAszQOu63miV_R5cfAW5a77Sw@mail.gmail.com
      Content-Type: text/plain; charset="iso-8859-1"
  Hi everybody !

  I'm developing an educative game.
  I've written a "gameEngine" class which does the logic for the

general
      progression in the game : switching between instances of morph
      subclasses which implement intro screen / mini-games/levels / end
      screen etc ...
  Now, i need to synchronize the instance of the gameEngine class

with
      the instances of the other classes.
      Example : once the gameEngine starts the instance of a morph
subclass
      which implements a mini-game, it must sleep until the mini-game is
      finished, and then wake up and does further required switching
(next
      mini-game or intro screen or end screen ...).
  i thought that a "simple" semaphore would quickly give a solution

to
      the problem.
      But i get a freezed code.
  I've modelized/simplified the problem with the following workspace

code.
      See also fileout of Class TestSynchro as attachment.
      TestSynchro has a step method which prints some lines to
Transcript,
      then calls the method stopStepping and signal to the semaphore.
      The workspace code does a wait, before printing to Transcript 'Hello
World'!
  Problem is that the code freezes , on the line code -> sem wait
  I first thought that the code freezed because in the same process.

And
      added a fork to the block which creates instance of TestSynchro.
But
      it does'nt help ...
  Any help will be appreciated !
  Thanks by advance,

  Patrick Dudjalija

  |ts sem|

  sem:=Semaphore new.

  [ts:= TestSynchro new.
  ts semaphore:sem.
  ts openInWorld.
  ts start.] fork.

  sem wait.
  Transcript cr; show:'Hello world !';cr.