Mercurial > rlm

     1 (ns rlm.iterate

     2   "from the clojure mailing list"

     3   {:author "tsuraan"}

     4   (:gen-class

     5    :name "iterate"

     6    :main true

     7    ))

     8 

     9 

    10 (set! *warn-on-reflection* true)

    11 (import java.io.FileInputStream)

    12 

    13 (def *numbytes* (* 16 1024 1024))

    14 

    15 

    16 (defmacro better-areduce [a idx ret init expr]

    17   `(let [a# ~a

    18 	 alength# (alength a#)]

    19      (loop [~idx (int 0) ~ret ~init]

    20        (if (< ~idx alength#)

    21 	 (recur (unchecked-inc ~idx) ~expr)

    22 	 ~ret))))

    23 

    24 (defn translated-countnl

    25   [#^bytes buf]

    26   (let [total-length (alength buf)]

    27     (loop [count (int 0) current-index (int 0)]

    28       (if (>= current-index total-length)

    29 	count

    30 	(let [new-count

    31 	      (if (= (aget #^bytes buf current-index) (byte 10))

    32 		(unchecked-inc count)

    33 		count)]

    34 	  

    35 	  (recur new-count (unchecked-inc current-index))))))) 

    36 	 

    37 (defn countnl-classic

    38   [#^bytes buf]

    39   (let [nl (byte 10)]

    40     (areduce buf idx count 0

    41 	     (if (= (aget buf idx) nl)

    42 	       (inc count)

    43 	       count))))

    44 

    45 

    46 (defn countnl-lite

    47   "this is the absolute fastest function I could come up with.

    48    still 2.25 times slower that the java version."

    49   [#^bytes buf]

    50   (areduce buf idx count (int 0)

    51 	   (if (= (clojure.lang.RT/aget buf idx) 10)

    52 	     (unchecked-add count 1)

    53 	     count)))

    54 

    55 

    56 (defn #^Boolean is-ten? [#^Integer A]

    57      (= A 10))

    58 

    59 (defn countnl-max-power

    60   [#^bytes buf]

    61   (areduce buf idx count (int 0)

    62 	   (if (is-ten? (clojure.lang.RT/aget buf idx))

    63 	     (unchecked-inc count)

    64 	     count)))

    65 

    66 

    67 

    68 

    69 			 

    70 			    

    71 

    72 			  

    73 	     

    74 

    75 

    76 "(times are averages with 10 rounds)

    77 no-modifications 

    78    classic:  198.151

    79    lite:     186.668

    80 

    81 unchecked-inc

    82    classic:  177.938

    83    lite:     129.604

    84 

    85 inlined-let

    86    classic:  202.604

    87    lite:     195.357

    88 

    89 make nl a constant

    90    classic:

    91    lite:     361.734

    92 

    93 make nl a constant with type hint

    94    lite:     394.45

    95 

    96 literal 10, no let

    97    lite:     102.876

    98 

    99  (int 10) instead of literal 10

   100    lite:     194.904

   101 

   102  (unchecked-add count 0) instead of count

   103    lite:     209.186

   104 

   105  direct reference to RT/aget, bypassing int cast

   106    lite:      99.767

   107 

   108  (int 0) instead of 0 initialization of count

   109    lite:      66.446

   110 

   111  make nl an (int 10) instead of (byte 10)

   112    lite:     180.003 

   113 "

   114 

   115 

   116 

   117 

   118 

   119 (defmacro time-multi

   120   "Evaluates expr and prints the time it took.  Returns the value of

   121  expr."

   122   {:added "1.0"}

   123   [expr]

   124   `(let [start# (. System (nanoTime))

   125          ret# ~expr

   126 	 end# (/ (double (- (. System (nanoTime)) start#)) 1000000.0)]

   127      (prn (str "Elapsed time: " end# " msecs"))

   128      [ret# end#]))

   129 

   130 

   131 

   132 (defn run [countnl-impl]

   133   (let [ifs (FileInputStream. "/dev/urandom")

   134 	buf (make-array Byte/TYPE *numbytes*)

   135 	runs 10]

   136     (loop [n 0 total-time 0]

   137       (if (= n runs) (/ total-time runs)

   138 	  (let [sz (.read #^FileInputStream ifs buf)]

   139 	    (println "Wanted" *numbytes* "got" sz "bytes")

   140 	    (let [[count time] (time-multi (countnl-impl buf))]

   141 	      (println "Got" count "nls")

   142 	      (recur (inc n) (+ total-time time))))))))

   143 

   144 (defn -main [& ignore]

   145   (run countnl-lite)

   146   (run countnl-classic)

   147   )

   148 

   149 

   150
author	Robert McIntyre <rlm@mit.edu>
date	Tue, 18 Oct 2011 00:57:08 -0700
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