On Wed, Feb 27, 2013 at 10:21 AM, Marko Topolnik
<marko.topol...@gmail.com>wrote:
>
> (defn blank? [s] (every? #(Character/isWhitespace %) s))
>>
>> Have you ever wondered about its performance? Here you go:
>>
>> user> (time (dotimes [_ 10000] (blank? "
>> ")))
>> "Elapsed time: 3887.578 msecs"
>>
>
> To give a more complete picture, this version
>
> (defn blank? [s] (every? #(Character/isWhitespace ^char %) s))
>
> is only six times slower than the expanded version, and keeping an eye on
> reflection warnings is not such a drag. So, if it could be demonstrated
> that in general the properly type-hinted, but otherwise idiomatic Clojure
> is not more than 10 times slower than idiomatic Java, I'd consider that at
> least a good starting point.
>
Now that reduce can be short-circuited, redifining every?, some and al on
top of it would yield some interesting gains:
(defn revery? [pred coll]
(reduce (fn [t x]
(if (pred x)
t
(reduced false))) true coll))
(defn rblank? [s] (revery? #(Character/isWhitespace ^char %) s))
(defn blank? [s] (every? #(Character/isWhitespace ^char %) s))
=> (dotimes [_ 10]
(time (dotimes [_ 100000] (blank? "
"))))
"Elapsed time: 515.371 msecs"
"Elapsed time: 500.408 msecs"
"Elapsed time: 507.646 msecs"
"Elapsed time: 644.074 msecs"
"Elapsed time: 529.717 msecs"
"Elapsed time: 482.813 msecs"
"Elapsed time: 557.563 msecs"
"Elapsed time: 486.573 msecs"
"Elapsed time: 493.636 msecs"
"Elapsed time: 481.357 msecs"
nil
=> (dotimes [_ 10]
(time (dotimes [_ 100000] (rblank? "
"))))
"Elapsed time: 227.692 msecs"
"Elapsed time: 99.937 msecs"
"Elapsed time: 95.922 msecs"
"Elapsed time: 91.193 msecs"
"Elapsed time: 90.794 msecs"
"Elapsed time: 94.765 msecs"
"Elapsed time: 89.842 msecs"
"Elapsed time: 120.551 msecs"
"Elapsed time: 90.843 msecs"
"Elapsed time: 93.523 msecs"
nil
Christophe
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