Given 4 bank accounts and 10 accountants, write a program to simulate the withdrawal and deposits done by accountants.

core.clj

(ns bank-acc-sim.core
  (:gen-class))

(import '(java.util.concurrent Executors))


(defn bank-sim [naccounts nthreads init-val niters]
  (let [refs  (map ref (repeat naccounts init-val))
        pool  (Executors/newFixedThreadPool nthreads)
        tasks (map
               (fn [tid]
                 (fn []
                   (dotimes [n niters]
                     (let [src    (rand-int naccounts)
                           dest   (rand-int naccounts)
                           offset (rand-int 10)]
                       (dosync
                        (alter (nth refs src)  (fn [v] (- v offset)))
                        (alter (nth refs dest) (fn [v] (+ v offset))))))))
               (range nthreads))]
    (doseq [future (.invokeAll pool tasks)]
      (.get future))
    (.shutdown pool)
    (map deref refs)))

;; (bank-sim 4 10 1000 (* 10 1000))

(defn -main
  "Eh..."
  [& args]
  (let [res (bank-sim 4 10 1000 (* 10 1000))]
    (println res)
    (println (reduce + res)))