[Numpy-discussion] Numpy arrays shareable among related processes (PR #7533)

[Allan Haldane]

On 05/11/2016 06:39 PM, Joe Kington wrote:
> 
> 
>     In python2 it appears that multiprocessing uses pickle protocol 0 which
>     must cause a big slowdown (a factor of 100) relative to protocol 2, and
>     uses pickle instead of cPickle.
> 
> 
> Even on Python 2.x, multiprocessing uses protocol 2, not protocol 0. 
> The default for the `pickle` module changed, but multiprocessing has
> always used a binary pickle protocol to communicate between processes. 
> Have a look at multiprocessing's forking.py <http://forking.py> in
> Python 2.7.

Are you sure? As far as I understood the code, it uses the default
protocol 0. The file forking.py no longer exists, also.

https://github.com/python/cpython/tree/master/Lib/multiprocessing
(see reduction.py and queue.py)
http://bugs.python.org/issue23403