On Aug 17, 3:51 am, Christophe Grand <christo...@cgrand.net> wrote: > On Sat, Aug 15, 2009 at 4:23 PM, Andy Fingerhut < > > andy_finger...@alum.wustl.edu> wrote: > > Not to say this ought to be done, but would it be possible to have no > > 'edit' field *at all* for persistent data structures (not even a null > > reference), and only an edit field at the "root" data structure of a > > transient (none of the children would have one, only the root), and > > preserve O(1) transient/persistent! calls? > > The problem is when you have several calls to transient/persistent! You have > to be able to tell transient nodes owned by the current transient processing > from older transient nodes left in place by previous calls to persistent!. > (and these transient nodes can be shared!) > One could have a set of nodes owned by the current transient but it would > incur some bookkeeping to not retain a reference to a reclaimable node. > I don't know if there's another way to do that.
But if there is only a single non-null edit reference in the "root node", then the non-root nodes don't really need a reference to the thread that is currently mutating the data structure, right? And after a call to peristent!, a different thread could later call transient on it, and want to make its own modified version. So any non-null edit references anywhere in the persistent data structure are useless, aren't they? > > But even if edit remains in all of them, I'm wondering whether it > > > could be maintained that only the root node has a non-null edit field, > > while that data structure is transient. > > Why do you focus on these AtomicReferences? If you contrast pre-transient > vectors and actual vectors you'll see that the overhead due to instance of > PersistentVector$Node is far more important. > > Christophe I only focus my questions on AtomicReferences because I noticed them. I haven't yet taken the time to read through all the source code related to the implementation of transient data structures. It just seems to me that a persistent data structure doesn't _need_ a reference to the thread that created it. It is now immutable, and it and all of its "sub-parts" always will be, until and unless they are deallocated by garbage collection. Thanks, Andy --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
