On Thu, Sep 17, 2009 at 11:12 AM, John Harrop <jharrop...@gmail.com> wrote: > On Thu, Sep 17, 2009 at 11:04 AM, Mark Volkmann <r.mark.volkm...@gmail.com> > wrote: >> >> On Thu, Sep 17, 2009 at 9:57 AM, Chouser <chou...@gmail.com> wrote: >> > >> > On Thu, Sep 17, 2009 at 12:28 AM, Krukow <karl.kru...@gmail.com> wrote: >> >> >> >> Final question. The docs say that 'ensure' permits more concurrency >> >> than promoting the ref to a write. Is there a quick/simple way of >> >> explaining how? (Or do I need to go to the source :-) >> > >> > If you have multiple transactions ensuring the same var but >> > no transactions changing it, all those transactions can >> > proceed simultaneously. If they all did dummy writes >> > instead of ensure, they could only proceed in order. >> >> Ah ... I think I misunderstood an important part of the question. I >> wasn't assuming that all the concurrent transactions were going to use >> ensure or a dummy write on the same Ref. So the key is that multiple >> transactions can successfully ensure the same Ref, but multiple >> transactions cannot successfully write the same Ref. > > Not with ref-set! or alter!, but maybe with commute identity?
I should have been more clear above. What I meant was that multiple concurrent transactions cannot write the same Ref without some of them having to retry. If you use commute instead of ref-set or alter then they don't have to retry. -- R. Mark Volkmann Object Computing, Inc. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
