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

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 beginners-request@lists.squeakfoundation.org:

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Today's Topics:

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

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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

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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

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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.