Antoine Pitrou <pit...@free.fr> added the comment: Le mercredi 17 décembre 2008 à 23:56 +0000, Daniel Stutzbach a écrit : > For tuples, I think the rule is: > If an object is immutable, and it points only to untracked objects, > the object can be untracked.
Roughly, yes. Exactly, it is "if it points only to untrackable objects". That is, a tuple containing an untracked dict will still be tracked, because the dict may mutate and become tracked later. But a tuple containing an untracked tuple will itself be untracked, because the enclosed tuple can't mutate. > Is that right? If so, you could perform the same optimization on the > frozenset() type. Yes, but I prefer to concentrate on those two core types now, which are the most frequent. Once the principle is accepted we can extend the implementation to other types. > Why do empty tuples have to be tracked? Actually, they are never tracked, which means calling _PyObject_GC_UNTRACK on them would segfault. > The dict patch adds a boolean flag to the dict data structure to > indicate whether the dict is being tracked or not. I think. Couldn't > you use _PyObject_GC_IS_TRACKED() instead? Yes, probably. I thought a dedicated flag may be faster but I will try without. > Do you > need to recheck the rule every time the dict is modified? Only if it is not tracked. Once a dict is tracked, it cannot become untracked again (there would be too much overhead, and the assumption is that you usually create homogeneous containers, you don't create a dict of mutable containers things and then replace the mutable containers with simple atomic objects). _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue4688> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
