[Python-Dev] Optimization of the Year

[Guido van Rossum]

> >  http://people.freebsd.org/~perky/list-r2.diff.txt
> 
> We have a winner.  It has most of the performance benefits with no 
> space trade-off.

(Except on Windows, if I understand Tim's comments.)

> It is not as automatic as the previous patch.
> The patch had to add code to list_sort() to trap the temporary
> alteration of ob_item.  If similar tricks get used in extensions,
> they will need to add "list->allocated = -1;" to invalidate the
> previous allocation size.
> 
> If there are no dissents, I will check this in.

I disagree with making the hack of setting list->allocated = -1 an
official part of the list object API.

The fact that list.sort() does this doesn't mean that other extensions
should do this!

Since you have ignored repeated requests for real-life examples of
code that messes with ob_item outside the core, let's keep the
'allocated' field an internal detail of the list implementation.  Then
I can ignore the other posts about binary (in)compatibility too. :-)

(Otherwise, you would have to write docs before checking it in.)

--Guido van Rossum (home page: http://www.python.org/~guido/)