Investigations on fast counting

count-enterprise-ed.clj

(require '[criterium.core :refer [quick-bench]])
(require '[clojure.core.reducers :as r])
(import 'java.util.concurrent.atomic.AtomicInteger)
(set! *warn-on-reflection* true)

(def data
  (into []
        (map hash-map
             (repeat :samplevalue)
             (concat
               (range 1e5)
               (range 1e5)
               (range 1e5)
               (range 1e5)
               (range 1e5)))))

(quick-bench
  (reduce + (map (constantly 1) (filter #(= 75584 (:samplevalue %)) data))))
;; Execution time mean : 47.112245 ms

(quick-bench
  (count (filter #(= 75584 (:samplevalue %)) data)))
;; Execution time mean : 32.594683 ms

(quick-bench
  (count
    (seq
      (eduction
        (map :samplevalue)
        data
        (filter #(= 75584 %))))))
;; Execution time mean : 25.140066 ms

(quick-bench
  (transduce
    (comp
      (map :samplevalue)
      (filter #(= 75584 %))
      (map (constantly 1)))
    +
    data))
;; Execution time mean : 25.215213 ms

(quick-bench
  (r/fold +
    ((comp
       (map :samplevalue)
       (filter #(= 75584 %))
       (map (constantly 1))) +)
    data))
;; Execution time mean : 13.732841 ms

(let [cnt (AtomicInteger. 0)
      combinef (fn ([] cnt) ([_ _]))
      rf (fn [^AtomicInteger cnt _] (.incrementAndGet cnt) cnt)
      reducef ((comp (map :samplevalue) (filter #(= 75584 %))) rf)]
  (quick-bench
    (do
      (r/fold combinef reducef data)
      (long cnt))))
;; Execution time mean : 13.525181 ms