Ah, thanks. The locking granularity is local to the cons cell (or analogue; first/rest pair) being realized, I hope? So one thread actually calculates an element and neither call returns until it's calculated, and then both promptly return the calculated value, but threads realizing other lazy seqs or crawling along earlier parts of the same one don't get blocked? (And given they can share tails, how would "same one" even be defined anyway?)
On Mon, Jun 24, 2013 at 5:56 PM, Nicola Mometto <brobro...@gmail.com> wrote: > > Realizing a lazy-seq is done through a synchronized method see: > > https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/LazySeq.java#L37 > > No race conditions. > > Cedric Greevey writes: > > > What, precisely, happens if two threads sharing a reference to a single > > lazy sequence try to realize the same element at the same time? If the > > sequence is completely pure and deterministic, so any attempt to realize > a > > particular element will produce a single particular value consistently > > (unlike, say, (repeatedly rand) or a file-seq where relevant parts of the > > filesystem are being concurrently modified), is the worst-case scenario > > that the two threads will redundantly perform the same calculation, with > no > > effect other than a minor hit to performance and, in particular, no > effect > > on the program semantics? > > > > -- > > -- > -- > 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 > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
