Clojure concat performance comparison

clojure-concat-performance-comparison.cljc

; Comparing 'normal' versus lazy concat

(apply concat [[:a] [:b] [:c :d] [:e :f :g] [:h]])
; => (:a :b :c :d :e :f :g :h)

(take 3 (apply concat [[:a] [:b] [:c :d] [:e :f :g] [:h]]))
; => (:a :b :c)


; normal concat

(take 3 (apply concat [[:a] [:b] [:c :d] [:e :f :g] [:h]]))
; => (:a :b :c)

(crit/quick-bench (take 3 (apply concat [[:a] [:b] [:c :d] [:e :f :g] [:h]])))
;                Evaluation count : 6014490 in 6 samples of 1002415 calls.
;             Execution time mean : 107,498409 ns
;    Execution time std-deviation : 18,745439 ns
;   Execution time lower quantile : 97,841913 ns ( 2,5%)
;   Execution time upper quantile : 139,617924 ns (97,5%)
;                   Overhead used : 1,593551 ns


; lazy-concat

(defn lazy-concat
  "Lazy version of `(apply concat s)`."
  [s]
  (lazy-cat (first s) (when-let [n (next s)] (lazy-concat n))))

(take 3 (lazy-concat [[:a] [:b] [:c :d] [:e :f :g] [:h]]))
; => (:a :b :c)

(crit/quick-bench (take 3 (lazy-concat [[:a] [:b] [:c :d] [:e :f :g] [:h]])))
;                Evaluation count : 21641268 in 6 samples of 3606878 calls.
;             Execution time mean : 27,053287 ns
;    Execution time std-deviation : 0,943091 ns
;   Execution time lower quantile : 25,955953 ns ( 2,5%)
;   Execution time upper quantile : 28,243797 ns (97,5%)
;                   Overhead used : 1,593551 ns


;; large lists

; normal concat

(first (apply concat [(sort > (range 10)) (sort > (range 1e7))]))
; => 9

(crit/quick-bench (first (apply concat [(sort > (range 10)) (sort > (range 1e7))])))
;                Evaluation count : 6 in 6 samples of 1 calls.
;             Execution time mean : 1,099606 sec
;    Execution time std-deviation : 333,110102 ms
;   Execution time lower quantile : 767,567999 ms ( 2,5%)
;   Execution time upper quantile : 1,623283 sec (97,5%)
;                   Overhead used : 1,593551 ns


; lazy-concat

(first (lazy-concat [(sort > (range 10)) (sort > (range 1e7))]))
; => 9

(crit/quick-bench (first (lazy-concat [(sort > (range 10)) (sort > (range 1e7))])))
;                Evaluation count : 6 in 6 samples of 1 calls.
;             Execution time mean : 999,570032 ms
;    Execution time std-deviation : 240,456317 ms
;   Execution time lower quantile : 788,094099 ms ( 2,5%)
;   Execution time upper quantile : 1,268182 sec (97,5%)
;                   Overhead used : 1,593551 ns


;; large number of lists

; normal concat

(first (apply concat (map (fn [_] (repeat 1024 :x)) (range 1e7))))
; => :x

(crit/quick-bench (first (apply concat (map (fn [_] (repeat 1024 :x)) (range 1e7)))))
;                Evaluation count : 719862 in 6 samples of 119977 calls.
;             Execution time mean : 836,555709 ns
;    Execution time std-deviation : 12,295324 ns
;   Execution time lower quantile : 821,947632 ns ( 2,5%)
;   Execution time upper quantile : 850,561449 ns (97,5%)
;                   Overhead used : 1,593551 ns

; lazy-concat

(first (lazy-concat (map (fn [_] (repeat 1024 :x)) (range 1e7))))
; => :x

(crit/quick-bench (first (lazy-concat (map (fn [_] (repeat 1024 :x)) (range 1e7)))))
;                Evaluation count : 795798 in 6 samples of 132633 calls.
;             Execution time mean : 766,662844 ns
;    Execution time std-deviation : 10,461101 ns
;   Execution time lower quantile : 759,661193 ns ( 2,5%)
;   Execution time upper quantile : 784,401171 ns (97,5%)
;                   Overhead used : 1,593551 ns