commute.clj

commute.clj

(ns testing.core)

(def start (atom 0)) ; Record start time.

(def c1 (ref 0)) ; Counter 1
(def c2 (ref 0)) ; Counter 2
(def c3 (ref 0)) ; Counter 3

(defn milliTime 
  "Get current time in millisecond."
  []
  (int (/ (System/nanoTime) 1000000)))

(defn lap 
  "Get elapse time since 'start' in millisecond."
  []
  (- (milliTime) @start))

(defn slow-inc
  "Slow increment, takes 1 second."
  [x x-name]
  (println "slow-inc beg" x-name ":" x "|" (lap) "ms")
  (Thread/sleep 1000)
  (println "slow-inc end" x-name ":" (inc x) "|" (lap) "ms")
  (inc x))

(defn fast-inc
  "Fast increment. The value it prints is incremented."
  [x x-name]
  (println "fast-inc    " x-name ":" (inc x) "|" (lap) "ms")
  (inc x))

(defn -main
  []
  ;; Initialize c1, c2, c3 and start.
  (dosync (ref-set c1 0) 
          (ref-set c2 0)
          (ref-set c3 0))
  (reset! start (milliTime))

  ;; Start two new threads simultaneously.
  (let [t1 (future
             (dosync
               (println "transaction start   |" (lap) "ms")
               (alter c1 slow-inc "c1")
               (alter c2 slow-inc "c2")
               (alter c3 slow-inc "c3")
               (println "transaction end     |" (lap) "ms")))
        t2 (future
            (Thread/sleep 900) ; Increment at 900 ms
              (dosync (alter c3 fast-inc "c3")))]

    ;; Dereference all of them (wait until all 2 threads finish).
    @t1 @t2 

    ;; Print final counters' values.
    (println "c1 :" @c1)
    (println "c2 :" @c2)
    (println "c3 :" @c3)))