Range is lazy.
First you define a range, which is just a promise that the variable will
be rendering a seq with 10M when asked for the elements.
When you count the sequence you realize it and it takes up much space. When
you let go if it it's of course GCed.
The problem is that you hold on to the head (first element) of the sequence.
If you do
(count (range 1000))
clojure will go through it lazily and throw away elements as they are
counted, hence much less memory usage.
Let go of the head! :)
/Linus
2011/10/25 Mike cki...@gmail.com
It appears I'm not understanding how something works in the REPL (or
maybe deeper). For instance:
(def big (range 1000))
; memory is small now
(count big) = 1000
; memory is huge now
(System/gc)
; memory is still huge now
(def big nil)
(System/gc)
; memory is small again
So somehow when count realizes big, I'm guessing it gets memoized
and stuck in some sort of cache attached to the var big.
If I:
(do (System/gc) (count (range 1000)) (System/gc))
; memory is small before and after
I think the version I wrote originally is fine; I just wasn't testing
it properly. Sorry to bother folks!
Mike
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