[Newbies] Simple semaphore to synchronize instances of different classes

Wed Aug 15 19:12:22 UTC 2012

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.

Thanks for any help.

Patrick Dudjalija

2012/8/15 patrick dudjalija <patrick.dudjalija at 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 at lists.squeakfoundation.org>
>
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>>    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 at gmail.com>
>> Subject: [Newbies] Simple semaphore to synchronize instances of
>>         different       classes
>> To: beginners <beginners at lists.squeakfoundation.org>
>> Message-ID:
>>         <CAEMqm6GttreSY5i+SA=Hg1=
>> C8sAszQOu63miV_R5cfAW5a77Sw at 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.
>> -------------- next part --------------
>> A non-text attachment was scrubbed...
>> Name: TestSynchro.st
>> Type: application/octet-stream
>> Size: 2201 bytes
>> Desc: not available
>> Url :
>> http://lists.squeakfoundation.org/pipermail/beginners/attachments/20120814/8d30cdd2/TestSynchro-0001.obj
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Tue, 14 Aug 2012 16:07:36 -0400
>> From: Chris Cunnington <smalltalktelevision at gmail.com>
>> Subject: Re: [Newbies] Simple semaphore to synchronize instances of
>>         different       classes
>> To: beginners at lists.squeakfoundation.org
>> Message-ID: <502AB008.3030104 at gmail.com>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>>
>> On 12-08-14 3:24 PM, patrick dudjalija wrote:
>> > 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 ad2vance,
>>
>> >
>> > 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.
>> >
>> >
>> > _______________________________________________
>> > Beginners mailing list
>> > Beginners at lists.squeakfoundation.org
>> > http://lists.squeakfoundation.org/mailman/listinfo/beginners
>>
>>
>> http://stephane.ducasse.free.fr/FreeBooks/GuzdialBookDrafts/BuildUI-ch5.pdf
>>
>> I don't know much about this stuff, but using Semaphore for animations
>> seems too low level. Pg. 53 of this pdf describes how step and stepTime
>> work.
>>
>> HTH,
>> Chris
>>
>>
>>
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