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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