[Python-Dev] iterzip()

[Guido van Rossum]

> The difficulty is with apps that grow a lot of long-lived containers
> that aren't trash and don't even contain cycles.  There's no bound
> on how often they'll get crawled over looking for trash that ain't
> there, and the more of those you grow the longer it takes to look at
> them.  When a gen2 collection doesn't find any trash, it should
> probably become less eager to try looking at the same stuff yet
> again.  Adding more generations could have a similar good effect.
> 
> Half of a shadow of an idea: at least in my code, it's common to
> have gazillions of tuples, and they almost always contain just
> strings and numbers.  Since they're immutable, they'll never contain
> anything else.  So they could get unlinked from cyclic gc entirely
> without ill effect (it's not possible that they could ever be in a
> cycle).  Perhaps a gen2 collection could learn something about this
> and automagically untrack them.

Different (complementary) idea: how about having more generations,
each being traversed less frequently than the previous one?  Maybe a
(potentially) infinite number of generations?  (Or at least a fixed
limit that never gets reached in practice.)  Wouldn't this have the
same effect as increasing the threshold exponentially?

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