John Brant a écrit :
> nicolas cellier wrote:
>> Michael van der Gulik a écrit :
>>
>>> Andreas is a great programmer, but the example he posted had a bug in
>>> it and the proposed fix was incorrect.
>>>
>>
>> The patch is correct in its Squeak context.
> 
> Unless I've missed some correction to the patch, the patch isn't 
> correct. For example, you'll get an "Invalid priority" walkback if you 
> try to evaluate the following using the patch:
>     [[Transcript show: 'works'; cr; flush] fork]
>         forkAt: Processor lowestPriority
> 

Yes it's a flaw. Easy to correct however.

> Furthermore, it allows lower priority processes to run before a process 
> forked at a higher priority. For example, here's an example, that should 
> open an inspector on #(1 2 3), but with the patch, it opens on inspector 
> on #(1 3 2). The process forked at the lowest priority is run before the 
> one forked at a higher priority.
> 
> [| queue |
> queue := SharedQueue new.
> [queue nextPut: 3] forkAt: Processor lowestPriority.
> queue nextPut: 1.
> [queue nextPut: 2] fork.
> (Delay forSeconds: 1) wait. "Hack to let the blocks finish"
> (Array
>     with: queue next
>     with: queue next
>     with: queue next) inspect] forkAt: Processor lowestPriority + 1
> 
> 

OK I like it.
Nothing in Andreas implementation would guaranty any 
children-determinism, that's a good point.

Your example is worse because results are counter intuitive.
That's a definitive argument.

So i take my vote back, and say only idiots don't change their mind.
Sorry Andreas, you'd better use an explicit "newProcess and an explicit 
#resume as suggested.

Nicolas

> To me, the existing behavior is deterministic. When you fork a process 
> at the same priority as the running parent process, then the new forked 
> process is added to the list of runnable processes at that priority. The 
> parent process continues to run until either a higher priority process 
> becomes runnable or it yields control. If a higher priority process 
> becomes runnable, then the parent process is suspended and added to the 
> end of the runnable processes at its priority. Since it is added at the 
> end of the runnable processes list, the forked process will resume 
> before the parent resumes.
> 
> 
> John Brant
> 
>