It corresponds to the execution of the LazySeq fn. That fn will be called once and only once, the rest of the data in the object is immutable and side-effect free and therefore does not need to be synchronized.
Timothy On Mon, Jun 24, 2013 at 8:51 PM, Cedric Greevey <cgree...@gmail.com> wrote: > I'm familiar with what "synchronized Type foo (args)" does -- my last > question was more about what aspect of a lazy seq the object with the > method corresponds to. Cons cell or similar subunit? I could read half of > clojure.lang, learn how all the various types of seq (Cons, LazySeq, > ChunkedSeq, etc...) work under the hood, and thereby eventually figure it > out, but it's probably a lot fewer man-hours of work for me to ask someone > who's already intimately familiar with that codebase and for him to > answer... > > > > On Mon, Jun 24, 2013 at 10:32 PM, Timothy Baldridge > <tbaldri...@gmail.com>wrote: > >> Reading the LazySeq.java file should make this all clear, but yes, no >> race conditions. >> >> >> https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/LazySeq.java#L37 >> >> Synchronized methods basically lock the current instance of the object >> while the method runs, so it is impossible for two threads to execute the >> lazy seq fn at the same time. >> >> Timothy >> >> >> On Mon, Jun 24, 2013 at 4:17 PM, Cedric Greevey <cgree...@gmail.com>wrote: >> >>> 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. >>> >>> >>> >> >> >> >> -- >> “One of the main causes of the fall of the Roman Empire was that–lacking >> zero–they had no way to indicate successful termination of their C >> programs.” >> (Robert Firth) >> >> -- >> -- >> 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. > > > -- “One of the main causes of the fall of the Roman Empire was that–lacking zero–they had no way to indicate successful termination of their C programs.” (Robert Firth) -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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