How do I make this code faster? And leaner, i.e., use less memory ?
It's a simple function to generate NUMKEYS strings of length
KEYLENGTH,
store them in a Java array then store them in a HashMap<String,Object>
hash-map. [it doesn't store them in the hash-map yet; but it
allocates it]
(set! *warn-on-reflection* true)
(def *valid-chars* [ \a \b \c \d \e \f \g \h \i \j \k \l \m
\n \o \p \q \r \s \t \u \v \w \x \u \z
\0 \1 \2 \3 \4 \5 \6 \7 \8 \9 ] )
(defn generate-random-keys [ numkeys keylength ]
(time
(let [ rand (new java.util.Random)
key (make-array Character/TYPE keylength) ;; :initial-
element \a))
keys (make-array String numkeys)
data (new java.util.HashMap (int numkeys))
]
(.println System/out (format "generating [%d] keys of length
[%d]" numkeys keylength ))
(dotimes [i numkeys]
(dotimes [j keylength]
(aset key j (nth *valid-chars* (. rand nextInt (int 36)))))
(let [tmp (String. #^chars key) ]
;; (.println System/out (format "keys[%d] => [%s]" i
tmp))
(aset keys i tmp)))
(.println System/out (format "inserting [%d] keys into HashMap"
numkeys)))))
(generate-random-keys 100000 1024) ;; 100k strings, 1024-chars each
The corresponding Java code (w/ the hash-insert omitted in the clojure
version)
runs in 5.5sec and uses 290MB.
This code runs (which omits the hash-insert) runs in 17.8sec and uses
353MB.
I thought that I added all of the casts and "warn-on-reflections" that
would help.
Also, I thought using Java data structures directly would bypass some
of Clojure's
overhead. What am I missing?
Granted, the initial memory allocated is
* for POJ, ~12MB
* for Clojure, ~90MB
That may or may not be relevant. It's hard to know w/ auto mem-mgmt.
CHICKEE
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