Processes not exiting

Piet van Oostrum piet at
Fri Jul 31 06:27:31 EDT 2009

>>>>> ma3mju <matt.urry at> (m) wrote:

>m> Hi all,
>m> I'm having trouble with multiprocessing I'm using it to speed up some
>m> simulations, I find for large queues when the process reaches the
>m> poison pill it does not exit whereas for smaller queues it works
>m> without any problems. Has anyone else had this trouble? Can anyone
>m> tell me a way around it? The code is in two files below.

How do you know it doesn't exit. You haven't shown any of your output.

I did discover a problem in your code, but it should cause an exception:

>m> #set off some of the easy workers on the hard work (maybe double
>m> number of hard)
>m> for i in range(0,num_hard_workers):
>m>     hard_work_queue.put(None)
>m>     hard_workers.append(multiprocessing.Process
>m> (target=GP.RandomWalkGeneralizationErrorParallel,args=
>m> (hard_work_queue,result_queue,)))
>m> #wait for all hard workers to finish
>m> for worker in hard_workers:
>m>     worker.join()

Here you create new hard workers, but you never start them. The join
should then give an exception when it reaches these.
Piet van Oostrum <piet at>
URL: [PGP 8DAE142BE17999C4]
Private email: piet at

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