Re: [Pyobjc-dev] parallel processing

[Ronald O. <ron...@ma...>]

On 28 Mar, 2009, at 13:43, Daniel Ashbrook wrote:

> What's the recommended way to do parallel processing under PyObjc? I
> assume that NSThreads are bound by the same GIL limitation that
> prevents parallel processing under standard python.
>
> I've been trying the processing/multiprocessing (depending on the
> verision) and almost have had good success; however, sometimes one or
> two of the processes will hang on trying to callback the function,
> presumably due to some weird interaction between the bridge and
> fork()ed processes.
>
> What else should I try?

As you noticed NSThreads are bound by the GIL, just as regular Python  
threads (as long as you try to run Python code obviously). I haven't  
tried using the multiprocessing library yet, I'd consider hanging  
processes a bug in either PyObjC or multiprocessing until proven  
otherwise.    I know there are issues when using the fork system call  
without exec in a process using Apple frameworks, that's a limitation  
in those frameworks and not caused by Python/PyObjC.

One option you could try is to spawn of a background program that does  
the actual calculation and have that use multiprocessing to make use  
of multiple processes.

I have a note for the archives: don't use pyprocessing, it's basicly  
dead at the moment (at least according to Jesse Noller, who wrote  
multiprocessing).

W.r.t. hanging processes: can you reproduce that in a standalone  
program?  I'm at Pycon at the moment and might be able to get access  
to Jesse Noller to help research the issue.

Ronald
>
> Thanks,
>
>
> dan
>
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