[Python-ideas] Cofunctions PEP - Revision 4

[Christian Tismer]

Hi Greg,

digged this thing up while looking into the current async discussion.

On 14.08.10 03:22, Greg Ewing wrote:
> M.-A. Lemburg wrote:
>
>> Greg Ewing wrote:
>
>>> In an application that requires thousands of small, cooperating
>>> processes,
>
>> Sure, and those use Stackless to solve the problem, which IMHO
>> provides a much more Pythonic approach to these things.
>
> At the expense of using a non-standard Python installation,
> though. I'm trying to design something that can be incorporated
> into standard Python and work without requiring any deep
> black magic. Guido has so far rejected any idea of merging
> Stackless into CPython.
>
> Also I gather that Stackless works by copying pieces of
> C stack around, which is probably more lightweight than using
> an OS thread, but not as light as it could be.
>

So, here I need to correct a bit.
What you are describing is the behavior of stackless 2.0,
also what the greenlet does (and eventlet then too for now).

The main thing that makes stackless 3.x so difficult _is_ that
it is as efficient as can be, because no stack slicing is done,
for 90 % of all code.

Stackless uses operations to unwind the C stack in most cases.
If this were possible in _all_ cases, then all the stack copying
would go away, and we had no machine code at all!

But the necessary change to Python would be quite heavy,
undoable for a small team.

I have left these ideas long time ago and did other projects.
But maybe things should be considered again, after the world
has changed so much. Maybe Python 4 could be decoupled
from the C stack.

cheers - Chris

-- 
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