Are you able to go to billions of items with the first version? I'm going to be using this to work with truly vast sequences, so if there's any sort of memory issue with the approach, I would expect it to be exposed at some point - given that I can only throw finite amounts of memory at this.
Can you see anything theoretically wrong with either approach? On Friday, June 8, 2012 1:03:37 AM UTC+1, Jorge Barrios wrote: > > The first version completes without problems. > Make sure your JVM has plenty of memory available to garbage collect. > Look at the -Xmx setting (for instance with leiningen :jvm-opts ["- > Xmx2g" "-server"]) > > REPL started; server listening on localhost port 18885 > user=> (def atoms '(a b c)) > #'user/atoms > user=> > user=> (defn get-ch [n] (map #(str n %) atoms)) > #'user/get-ch > user=> (defn add-ch > ([] (apply concat (iterate add-ch atoms))) > ([n] (mapcat get-ch n))) > #'user/add-ch > user=> (time (dorun (take 20000000 (add-ch)))) > "Elapsed time: 89922.105 msecs" > nil > user=> > > On Jun 7, 10:53 am, Tom Hume <twh...@gmail.com> wrote: > > Hi > > > > I'm trying to generate a sequence which corresponds to a breadth-first > > search of a very wide, deep tree... and I'm hitting memory problems when > I > > go too far along the sequence. Having asked around on the IRC channel > and > > looked here, the number 1 cause of such problems is inadvertently > holding > > onto the head; but I can't see where I'm doing this. > > > > The code is quite simple; here's a version which displays the problem: > > > > (def atoms '(a b c)) > > > > (defn get-ch [n] (map #(str n %) atoms)) > > > > (defn add-ch > > ([] (apply concat (iterate add-ch atoms))) > > ([n] (mapcat get-ch n))) > > > > (dorun (take 20000000 (add-ch))) > > And here's another version (which is the one I started out with before > > getting help from #clojure), which displays the same issue: > > > > (def atoms '(a b c)) > > > > (defn get-children [n] (map #(str n %) atoms)) > > > > (defn add-layer > > ([] (add-layer atoms)) > > ([n] (let [child-nodes (mapcat get-children n) ] > > (lazy-seq (concat n (add-layer child-nodes)))))) > > > > (dorun (take 20000000 (add-layer))) > > Both give me an "OutOfMemoryError Java heap space". I'm running them > from > > the REPL in Eclipse/CounterClockwise, on a Macbook Air. > > > > I'm pretty new to Clojure, so after beating my head against this for a > day > > I'm hoping that this is something trivial I'm overlooking. I realise I > > could up my heap-size to make the issue less likely to occur, but the > > sequences I ultimately want to process are so vast I don't think this is > > going to help me... > > > > Any suggestions warmly welcomed. > > > > Thanks > > Tom -- 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
