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
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