[Stackless] multi-core processing?

Simon Pickles sipickles at googlemail.com
Mon Jun 16 14:39:07 CEST 2008

Chris Lee wrote:
> On Jun 15, 2008, at 10:33 PM, Jeff Senn wrote:
>> On Jun 15, 2008, at 3:57 PM, Simon Pickles wrote:
>>> Hi NRB,
>>> Neutral Robot Boy wrote:
>>>> alright, so i'm still in 'beginner' mode with stackless here. i did 
>>>> a bit of reading which suggested that stackless should be able to 
>>>> distribute processing across multiple cores without trouble, and i 
>>>> decided to write a really simple script and look at how much of a 
>>>> load it puts on my cpu.
>>> The stackless scheduler which you activate by calling 
>>> stackless.run() only runs in one thread. Each tasklet is added to 
>>> that scheduler and called in turn. No other core will be used.
>> I suppose one should point out that this is not merely a limitation 
>> of Stackless.
>> e.g. running schedulers in more than one thread won't even help.
>> Python itself, even using multiple native threads, can only make use 
>> of one core
>> at a time due to the GIL (Global Interpreter Lock).  If you are 
>> interested
>> in the whys-and-wherefores, a search through the archives of this list
>> (and/or Google) will provide a bunch of discussions.
>> -Jas
> Yes indeed, I run simulation code which can benefit from as many cores 
> and processors that are available. To achieve this in python I used 
> parallelpython, which acts as a job server and pickles the parameters, 
> modules, and functions for use by a new instance of python. Using 
> this, I can pretty much use all the processing power available on the 
> computer. It can even run across multiple machines, if I go to the 
> trouble to set up the permissions on each machine.
> ___
Please comment on the following statement:

"Due to the GIL, python threads will not operate concurrently on a 
multicore machine, even stackless ones. However, using multiple 
processes overcomes this problem, either by multiple instances of python 
running, by using the process module, or pyro, etc"

Hold true? (fingers crossed!)

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