Well not exactly what you said cause I'm lazy, but a little bit more
controlled:
timereference.clj:
(println "Java: "(System/getProperty "java.version"))
(println (clojure-version))
(dotimes [y 10]
(print "volatile: ")
(time
(let [v (volatile! 1)]
(dotimes [x 100000000]
(vreset! v @v))))
(print "AtomicLong: ")
(time
(let [v (java.util.concurrent.atomic.AtomicLong. 1)]
(dotimes [x 100000000]
(.set v (.get v)))))
(print "AtomicReference: ")
(time
(let [v (java.util.concurrent.atomic.AtomicReference. {})]
(dotimes [x 100000000]
(.set v (.get v)))))
(print "atom: ")
(time
(let [v (atom 1)]
(dotimes [x 100000000]
(reset! v @v)))))
[bmillare@sakura ~]$ java -server -cp
.m2/repository/org/clojure/clojure/1.7.0-alpha5/clojure-1.7.0-alpha5.jar
clojure.main timereference.clj
Java: 1.7.0_75
1.7.0-alpha5
volatile: "Elapsed time: 793.525092 msecs"
AtomicLong: "Elapsed time: 606.658899 msecs"
AtomicReference: "Elapsed time: 606.253989 msecs"
atom: "Elapsed time: 881.198546 msecs"
volatile: "Elapsed time: 787.714655 msecs"
AtomicLong: "Elapsed time: 603.810759 msecs"
AtomicReference: "Elapsed time: 603.811366 msecs"
atom: "Elapsed time: 1417.625552 msecs"
volatile: "Elapsed time: 794.154652 msecs"
AtomicLong: "Elapsed time: 603.718131 msecs"
AtomicReference: "Elapsed time: 603.723479 msecs"
atom: "Elapsed time: 866.220579 msecs"
volatile: "Elapsed time: 787.459397 msecs"
AtomicLong: "Elapsed time: 603.735881 msecs"
AtomicReference: "Elapsed time: 603.720108 msecs"
atom: "Elapsed time: 866.208679 msecs"
volatile: "Elapsed time: 787.455661 msecs"
AtomicLong: "Elapsed time: 603.720906 msecs"
AtomicReference: "Elapsed time: 603.735316 msecs"
atom: "Elapsed time: 866.226066 msecs"
volatile: "Elapsed time: 787.455482 msecs"
AtomicLong: "Elapsed time: 603.720222 msecs"
AtomicReference: "Elapsed time: 603.718667 msecs"
atom: "Elapsed time: 866.205402 msecs"
volatile: "Elapsed time: 789.429405 msecs"
AtomicLong: "Elapsed time: 603.71242 msecs"
AtomicReference: "Elapsed time: 603.717922 msecs"
atom: "Elapsed time: 866.212896 msecs"
volatile: "Elapsed time: 787.461736 msecs"
AtomicLong: "Elapsed time: 603.728396 msecs"
AtomicReference: "Elapsed time: 603.727234 msecs"
atom: "Elapsed time: 866.203579 msecs"
volatile: "Elapsed time: 787.462185 msecs"
AtomicLong: "Elapsed time: 603.721207 msecs"
AtomicReference: "Elapsed time: 603.716769 msecs"
atom: "Elapsed time: 866.207913 msecs"
volatile: "Elapsed time: 787.468805 msecs"
AtomicLong: "Elapsed time: 603.721715 msecs"
AtomicReference: "Elapsed time: 603.73172 msecs"
atom: "Elapsed time: 866.210223 msecs"
On Wednesday, March 11, 2015 at 11:57:50 AM UTC-4, tbc++ wrote:
>
> This is interesting, but there could be many things in play here. Try
> re-running the tests outside of lein (via compilation to a uberjar and then
> running with java -jar) and also use criterium, as it will warn about many
> things that coul effect performance .
>
> https://github.com/hugoduncan/criterium
>
> Timothy Baldridge
>
> On Wed, Mar 11, 2015 at 9:38 AM, Brent Millare <[email protected]
> <javascript:>> wrote:
>
>> Doing some simple microbenchmarks, I found something unexpected:
>>
>> (time
>> (let [v (volatile! 1)]
>> (dotimes [x 100000000]
>> (vreset! v @v))))
>> "Elapsed time: 1016.992146 msecs"
>>
>> (time
>> (let [v (java.util.concurrent.atomic.AtomicLong. 1)]
>> (dotimes [x 100000000]
>> (.set v (.get v)))))
>> "Elapsed time: 672.869727 msecs"
>>
>> (time
>> (let [v (java.util.concurrent.atomic.AtomicReference. {})]
>> (dotimes [x 100000000]
>> (.set v (.get v)))))
>> "Elapsed time: 678.143133 msecs"
>>
>> (time
>> (let [v (atom 1)]
>> (dotimes [x 100000000]
>> (reset! v @v))))
>> "Elapsed time: 1100.689493 msecs"
>>
>> I expected volatile's to be faster. Maybe I'm not understanding the
>> correct use case for volatiles but java.util.concurrent.atomic.Atomic*
>> seems to be clearly the most performant. Given the downsides of using
>> volatiles, is their existence justified when safer and faster alternatives
>> exist?
>>
>> --
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>
>
>
> --
> “One of the main causes of the fall of the Roman Empire was that–lacking
> zero–they had no way to indicate successful termination of their C
> programs.”
> (Robert Firth)
>
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