Hi
On Mon, Feb 4, 2013 at 2:29 PM, AtKaaZ <atk...@gmail.com> wrote:
> => (class {:x "a" :y 3})
> clojure.lang.Persistent*Array*Map
> => (def m {:x "a" :y 3})
> #'runtime.q/m
> => (class m)
> clojure.lang.Persistent*Hash*Map
>
huh? that one I can't explain, I'll have to do some research.
=> (def m (let [] {:x "a" :y 3}))
#'user/m
=> (class m)
clojure.lang.PersistentArrayMap
> => (time (dotimes [n 10000000] (hash m)))
> "Elapsed time: 168.162927 msecs"
> nil
> => (time (dotimes [n 10000000] (hash m)))
> "Elapsed time: 161.341094 msecs"
> nil
> => (time (dotimes [n 10000000] (hash m)))
> "Elapsed time: 159.444025 msecs"
> nil
>
>
Since hash is cached and m doesn't change, more runs are just measuring the
time to lookup the cache. There may be a sligt overhead due to m being a
var.
To properly isolate this you have to use locals:
=> (let [m (hash-map :x "a" :y 3)]
(println (class m))
(time (dotimes [n 10000000] (hash m))))
clojure.lang.PersistentHashMap
"Elapsed time: 221.62 msecs"
nil
=> (let [m (hash-map :x "a" :y 3)]
(println (class m))
(time (dotimes [n 10000000] (hash m))))
clojure.lang.PersistentHashMap
"Elapsed time: 214.624 msecs"
nil
=> (let [m (hash-map :x "a" :y 3)]
(println (class m))
(time (dotimes [n 10000000] (hash m))))
clojure.lang.PersistentHashMap
"Elapsed time: 212.505 msecs"
nil
=> (let [m {:x "a" :y 3}]
(println (class m))
(time (dotimes [n 10000000] (hash m))))
clojure.lang.PersistentArrayMap
"Elapsed time: 232.872 msecs"
nil
=> (let [m {:x "a" :y 3}]
(println (class m))
(time (dotimes [n 10000000] (hash m))))
clojure.lang.PersistentArrayMap
"Elapsed time: 218.141 msecs"
nil
=> (let [m {:x "a" :y 3}]
(println (class m))
(time (dotimes [n 10000000] (hash m))))
clojure.lang.PersistentArrayMap
"Elapsed time: 220.813 msecs"
nil
No significant change -- hopefully since 1e7-1 times out od 1z7 we are
measuring the cost of looking up a cache.
Christophe
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