Home Original page

Cyclops 0.9.4

Tim Peters tim_one at email.msn.com
Tue Jul 20 02:31:49 EDT 1999 
[nascheme at ucalgary.ca]
> [This message has also been posted.]

Ditto.

> Cool.  How about a feature that displays only cycles created
> since a marking function was called.  I think this would be most
> useful in programs that leak memory.  You don't care if cycles
> exist, you just don't want them to be continually created.  The
> way I see this working is you start up something like IDLE, do
> some stuff, call the marking function, do more stuff, call cycle
> showing function.

You can do this yourself by installing a cycle filter, that returns false
whenever it sees a cycle that's been seen before.  I don't think it could be
done more efficiently than that if implemented inside Cyclops, although
Cyclops knows how to subtract its internal references from the refcounts
delivered via get_rootset().  A user-written cycle filter can do that too
for its own references, but it is a little tricky to get straight.

Simpler, just call find_cycles() followed by show_stats() from time to time.
One of the output lines is "# cycles found: <n>".  New cycles are being
found if & only if n is increasing.

Now if you actually *try* any of these and find them helpful in "real life",
pass it on!  My experience in IDLE was that cycles weren't actually causing
the leaks, although up until it hit a dead end they were correlated with
leaks; the real cause was references in basic (reachable) objects that
weren't getting cleared out when the widgets they referenced got closed.

enough-to-make-you-dizzy-ly y'rs  - tim
More information about the Python-list mailing list