Solving the problem of mutual recursion

[Carlos Nepomuceno]

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> Date: Sun, 26 May 2013 10:21:05 -0700
> Subject: Re: Solving the problem of mutual recursion
> From: peter.h.m.brooks at gmail.com
> To: python-list at python.org
>
> On May 26, 5:09 pm, Jussi Piitulainen <jpiit... at ling.helsinki.fi>
> wrote:
>>
>> A light-weighter way is to have each task end by assigning the next
>> task and returning, instead of calling the next task directly. When a
>> task returns, a driver loop will call the assigned task, which again
>> does a bounded amount of work, assigns the next task, and returns.
>> Tasks can even pass parameters in the same way.
>>
> Yes, that's true - there are a number of ways of making it linear.
>
> What I'm particularly pleased about with my method is the parallelism
> that it achieves - with so little effort! The simulation is going to
> be computationally intense and this is going to make sure that the
> CPUs are all giving it their best shot. When I run this on my macbook,
> the python interpreter takes over 140% of CPU - with a bit of fine-
> tuning, it should be possible to have more concurrent threads and to
> use the four cores optimally.
>
> Naturally I'll need to be careful with the concurrency, but this is so
> simple and clean that it should be easy to avoid the main problems
> with accessing the same variables.
> --
> http://mail.python.org/mailman/listinfo/python-list

Python threads run in the same process and won't run concurrently:

"CPython implementation detail: In CPython, due to the Global Interpreter Lock, only one thread can execute Python code at once (even though certain performance-oriented libraries might overcome this limitation). If you want your application to make better use of the computational resources of multi-core machines, you are advised to use multiprocessing. However, threading is still an appropriate model if you want to run multiple I/O-bound tasks simultaneously."[1]

How can you get 140% of CPU? IS that a typo??

[1] http://docs.python.org/2/library/threading.html