l-cache.clj

(ns l-cache)

(set! clojure.core/*warn-on-reflection* true)

(defmacro with-time
  "Evaluates expr and returns a vector of expression value and the
  time it took to evaluate it in milliseconds."
  [expr]
  `(let [start# (System/nanoTime)
         ret# ~expr
         t# (/ (double (- (System/nanoTime) start#)) 1e6)]
     [ret# t#]))

(defn power-bytes [power]
  (* (Math/pow 2 power) 1e3))

(defn fill-array! [array val]
  (dotimes [i (count array)]
    (aset array i val)))

(defn get-array [array]
  (dotimes [i (count array)]
    (aget array i)))


(defn copy-array [array]
  (let [half-array-length (/ (count array) 2)]
    (System/arraycopy array 0 array half-array-length half-array-length)))

;(copy-array (make-array Byte/TYPE 1e3))
;(byte (rand 256))

(def results
     (for [p (range 9 15)]
       (let [b (* (Math/pow 2 p) 1e3)
             a (make-array Byte/TYPE b)
             [_ t] (with-time (dotimes [_ 10] (copy-array a)))]
         [b (/ t 10)])))

(println results)
;(reduce (fn [[b0 t0] [b1 t1]] [(/ b1 b0)]))

l_cache.clj

;;;; Copyright (c) 2009 Dimitry Gashinsky. No rights reserved.
;;;;
;;;; Author: Dimitry Gashinsky (dimitry :at gashinsky :dot com)
;;;; Id: c2f37c50-0c78-4973-9617-fbf91aeab8a6

(ns l-cache
  (:use [incanter core charts stats]
        [clojure.contrib pprint]))

(set! clojure.core/*warn-on-reflection* true)

(defmacro with-time
  "Evaluates expr and returns a vector of expression value and the
  time it took to evaluate it in milliseconds."
  [expr]
  `(let [start# (System/nanoTime)
         ret# ~expr
         t# (/ (double (- (System/nanoTime) start#)) 1e6)]
     [ret# t#]))

(defn mirror-part-array [array length]
  "Copy the first half of the array into the second."
  (let [half-length (/ length 2)]
    (System/arraycopy array 0 array half-length half-length)
    half-length))

(def *lab-array* (make-array Byte/TYPE (Math/pow 2 26)))

(def results
     (doall
      (for [p (range 20 26) v (range -1e6 1e6 1e3)]
        (let [b (+ (Math/pow 2 p) v)
              [l t] (with-time (mirror-part-array *lab-array* b))]
          [b (/ l t)]))))


;; (pprint results)

(def speed (map second results))
;; (view (xy-plot speed (variance speed)))
;; (reduce (fn [[b0 t0] [b1 t1]] [(/ b1 b0)]))

(set! clojure.core/*warn-on-reflection* false)

(def plot (xy-plot (map first results) (map second results)
                        :title "L1 and L2 Data Cache"
                        :x-label "bytes"
                        :y-label "bytes/milliseconds"))

(view plot)

(save plot
      "/tmp/l-cache.png"
      :width 1024
      :height 768)

(view "file:///tmp/l-cache.png")