While updating the benchmark programs I wrote for the shootout web
site for 1.3 alpha1, I came across a program that required much more
memory to complete in 1.3 than it did in 1.2. I boiled it down to a
simpler program that has similar properties.
----------------------------------------
(ns filestr2
(:gen-class))
(defn -main [& args]
(with-open [br (java.io.BufferedReader. *in*)]
(let [dna-str (apply str (line-seq br))]
(println "len=" (count dna-str))))
(. System (exit 0)))
----------------------------------------
I've checked that the function apply, str, and line-seq are identical
between those two Clojure versions, except for a few minor things like
type declarations and static declarations added in 1.3.0-alpha1.
I'm curious if anyone can explain the cause of this significant extra
memory. As an example of what I mean, when run on an input file with
about 125 million characters, it requires 932 Mbytes with Clojure 1.2,
but 1,736 Mbytes with Clojure 1.3 alpha1 (using the -Xmx command line
option to the JVM). That was on my Mac, and I've seen similar but not
identical results on an Ubuntu system. You can read more details if
you are curious in the README file of this tarball:
http://homepage.mac.com/jafingerhut/files/private/toomuch1.tar.bz2
It also includes a program that uses binary search to find the
smallest memory required in order for the program to succeed, to the
nearest 8 MB.
Thanks,
Andy
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