Hi,
your comparison is not fair. The map example merely assoc's a new value,
while in the record case you create a complete fresh value with a different
type. Here some more comparisons:
user=> (defrecord Foo [a b])
user.Foo
user=> (defrecord Bar [a b c])
user.Bar
user=> (let [x (->Foo 10 20)] (time (assoc (map->Bar x) :c 30)))
"Elapsed time: 0.130464 msecs"
#user.Bar{:a 10, :b 20, :c 30}
user=> (let [x (->Foo 10 20)] (time (->Bar (:a x) (:b x) 30)))
"Elapsed time: 0.288585 msecs"
#user.Bar{:a 10, :b 20, :c 30}
user=> (let [x {:a 10 :b 20}] (time (assoc (into {} x) :c 30)))
"Elapsed time: 2.231289 msecs"
{:c 30, :a 10, :b 20}
user=> (let [x (->Bar 10 20 0)] (time (assoc x :c 30)))
"Elapsed time: 0.011454 msecs"
#user.Bar{:a 10, :b 20, :c 30}
user=> (let [x {:a 10 :b 20}] (time (assoc x :c 30)))
"Elapsed time: 0.042743 msecs"
{:c 30, :a 10, :b 20}
To get more realistic numbers I strongly suggest to use
criterium<https://github.com/hugoduncan/criterium>for benchmarking, which
coincidentally just released a new version.
Kind regards,
Meikel
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