[Python-Dev] Looking for master thesis ideas involving Python

Phillip J. Eby pje at telecommunity.com
Mon Nov 3 11:38:52 EST 2003

At 11:35 AM 11/3/03 +0000, Michael Hudson wrote:
>Armin Rigo <arigo at tunes.org> writes:
> > What seems to me like a good solution would be to use one relatively
> > large "arena" per type and Python's memory allocator to subdivide
> > each arena.  If each arena starts at a pointer address which is
> > properly aligned, then *(p&MASK) gives you the type of any object,
> > and possibly even without much cache-miss overhead because there are
> > not so many arenas in total (probably only 1-2 per type in common
> > cases, and arenas can be large).
>Hmm, maybe.  I'm not going to make guesses about that one :-)

You guys do realize that this scheme would make it impossible to change an 
object's type, right?  Unless of course you have some way to "search and 
replace" all references to an object.

And if you were to say, "well, we'll only use this trick for non-heap 
types", my question would be, how's the code doing *(p&MASK) going to know 
how *not* to do that?  If heap types have a different layout, how can you 
inherit from a builtin type in pure Python?  And so on.

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