1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/src/rlm/function_utils.clj	Tue Oct 18 00:57:08 2011 -0700
     1.3 @@ -0,0 +1,185 @@
     1.4 +;; Various Operators on Pure Functions
     1.5 +;;
     1.6 +;; Open source Liscence and all that
     1.7 +(ns 
     1.8 +    rlm.function-utils
     1.9 +  "Collection of Operators on Pure Functions"
    1.10 +  {:author "Robert McIntyre"}
    1.11 +  (:use [clojure.contrib.profile]))
    1.12 +
    1.13 +(def void ::void)
    1.14 +
    1.15 +(comment
    1.16 +
    1.17 +  "Please help me out here.  I'm trying to make a higher order function that takes
    1.18 +   pure functions that are mathmaticaly the same but have different times and returns another
    1.19 +   function that runs them both and returns the resut of the one that finishes first."
    1.20 +
    1.21 +
    1.22 +  "here's a repl session:
    1.23 +
    1.24 +mobius> " (time (dotimes [_ 500]((mix-futures + +) 40 3 3 3 3 3))) "
    1.25 +Elapsed time: 85.792995 msecs
    1.26 +nil
    1.27 +mobius> " (time (dotimes [_ 500](+ 40 3 3 3 3 3))) "
    1.28 +Elapsed time: 6.956338 msecs
    1.29 +nil
    1.30 +mobius> " (time (dotimes [_ 500]((mix-threads + +) 40 3 3 3 3 3))) "
    1.31 +Elapsed time: 706.227065 msecs
    1.32 +nil
    1.33 +
    1.34 +
    1.35 +mobius> " (defn fast-five [& args] 5) "
    1.36 +#'mobius/fast-five
    1.37 +
    1.38 +mobius> " (defn slow-five [& args] (Thread/sleep 5000) (println "Oh YEAH!!!!") 5) "
    1.39 +#'mobius/slow-five
    1.40 +
    1.41 +mobius> " (profile (time (dotimes [_ 5000] (thread-five)))) "
    1.42 +\"Elapsed time: 12187.981587 msecs\"
    1.43 +          Name      mean       min       max     count       sum
    1.44 +   create-atom      9621      2025   4433928      5000  48106830
    1.45 +create-threads      5156      2724   2880268      5000  25783796
    1.46 +  kill-threads     91313     27866  11175718      5000  456567066
    1.47 +          loop   2124249     38482  18470781      5000  10621249899
    1.48 +        return      1242       838      5309      5000   6212626
    1.49 + start-threads    252985    110348  12272835      5000  1264927953
    1.50 +nil
    1.51 +
    1.52 +mobius> " (profile (time (dotimes [_ 5000] (future-five)))) "
    1.53 +\"Elapsed time: 607.266671 msecs\"
    1.54 +          Name      mean       min       max     count       sum
    1.55 +   create-atom      1472      1047     31708      5000   7363139
    1.56 +create-futures     30539      2514   1330660      5000  152697998
    1.57 +  kill-threads     54158      2444   3938833      5000  270792897
    1.58 +          loop     81117      8800   6083059      5000  405587516
    1.59 +        return      1215       838    618782      5000   6078146
    1.60 +nil
    1.61 +
    1.62 +
    1.63 +
    1.64 +What can I improve here, and why is the future version sooo much faster than the
    1.65 +thread version? Is there a better way than using loop?
    1.66 +"
    1.67 +
    1.68 +)
    1.69 +
    1.70 +
    1.71 +(defn mix 
    1.72 +  "Takes any number of mathematically equal functions with
    1.73 +   possibly different run-times and returns a function that
    1.74 +   runs each in a separate thread, returns the result from
    1.75 +   the first thread which finishes, and cancels the other threads."
    1.76 +  {:author "Robert McIntyre"}
    1.77 +  ([& functions]
    1.78 +     (fn [& args]
    1.79 +       (let [result (promise)
    1.80 +	     futures (doall (for [fun functions]
    1.81 +			      (future (deliver result (apply fun args)))))
    1.82 +	     answer @result]
    1.83 +	 (dorun (map future-cancel futures))
    1.84 +	 answer))))
    1.85 +
    1.86 +
    1.87 +
    1.88 +
    1.89 +(defn mix-threads
    1.90 +  " Takes any number of pure functions that take the same arguments and
    1.91 +   compute the same value and returns a function that runs each in a separate
    1.92 +   thread, returns the result from the first thread which finshes, and cancels 
    1.93 +   the other threads. Explicitly uses nasty Threads.
    1.94 +
    1.95 +   For example: 
    1.96 +   (do
    1.97 +   (defn fun1 [] (Thread/sleep 5000) 5)
    1.98 +   (defn fun2 [] (Thread/sleep 700000) 5)
    1.99 +   (time ((mix fun1 fun2))))
   1.100 +   
   1.101 +   Returns: 
   1.102 +    | Elapsed time: 5000.66214 msecs
   1.103 +   5"
   1.104 +  [& functions]
   1.105 +  (fn [& args]
   1.106 +    (let [result (prof :create-atom (atom void))
   1.107 +	  threads
   1.108 +	   (prof :create-threads (map 
   1.109 +	   (fn [fun] 
   1.110 +	     (Thread. 
   1.111 +	      (fn [] 
   1.112 +		(try (let [answer (apply fun args)]
   1.113 +		       (reset! result answer))
   1.114 +		     (catch Exception _ nil)))))
   1.115 +	   functions))]
   1.116 +      
   1.117 +      (prof :start-threads (dorun (map #(.start %) threads)))
   1.118 +      (prof :loop (loop []
   1.119 +	(if (=  (deref result) void)
   1.120 +	  (recur)
   1.121 +	  (do (prof :kill-threads (dorun (map #(.stop %) threads)))
   1.122 +	      (prof :return (deref result)))
   1.123 +	  ))))))
   1.124 +
   1.125 +(defmacro defmix
   1.126 +  " Defines a function from any number of pure functions that take the same 
   1.127 +   arguments and compute the same value which:
   1.128 +
   1.129 +   Runs each in a separate thread.
   1.130 +   Returns the result from the first thread which finshes.
   1.131 +   Cancels the other threads.
   1.132 +           
   1.133 +   Use this whenever you want to combine two pure functions that
   1.134 +   compute the same thing, but use different algorithms with different
   1.135 +   run times for various inputs.
   1.136 +
   1.137 +   For example: 
   1.138 +     (do
   1.139 +     (defn fun1 [] (Thread/sleep 5000) 5)
   1.140 +     (defn fun2 [] (Thread/sleep 700000) 5)
   1.141 +     (defmix fun3 \"combination of fun1 and fun2\" fun1 fun2)
   1.142 +     (time (fun3))
   1.143 +   
   1.144 +   Returns: 
   1.145 +     | Elapsed time: 5000.66214 msecs
   1.146 +     5"
   1.147 +
   1.148 +{:arglists '([name doc-string? functions*])}
   1.149 +
   1.150 +  [name & functions]
   1.151 +  (let [doc-string (if (string? (first functions)) (first functions) "")
   1.152 +	functions (if (string? (first functions)) (rest functions) functions)
   1.153 +	arglists (:arglists (meta (resolve (eval `(quote ~(first functions))))))
   1.154 +	name (with-meta name (assoc (meta name) :arglists `(quote ~arglists) :doc doc-string))]   
   1.155 +    `(def ~name (mix ~@functions))))
   1.156 +
   1.157 +
   1.158 +(defn runonce
   1.159 +  "Decorator.  returns a function which will run only once. Inspired
   1.160 +   by Halloway's version from lancet."
   1.161 +  {:author "Robert McIntyre"}
   1.162 +  [function]
   1.163 +  (let [sentinel (Object.) 
   1.164 +	result (atom sentinel)]
   1.165 +    (fn [& args]
   1.166 +       (locking sentinel
   1.167 +	 (if (= @result sentinel) 
   1.168 +	   (reset! result (apply function args)) 
   1.169 +	    @result)))))
   1.170 +
   1.171 +
   1.172 +
   1.173 +;I'm thinking this will be the docstring for mix eventually.
   1.174 +
   1.175 +  ;; " Takes any number of pure functions that take the same arguments and
   1.176 +  ;;  compute the same value and returns a function that runs each in a separate
   1.177 +  ;;  thread, returns the result from the first thread which finshes, and cancels 
   1.178 +  ;;  the other threads.
   1.179 +
   1.180 +  ;;  For example: 
   1.181 +  ;;  (do
   1.182 +  ;;  (defn fun1 [] (Thread/sleep 5000) 5)
   1.183 +  ;;  (defn fun2 [] (Thread/sleep 700000) 5)
   1.184 +  ;;  (time ((mix fun1 fun2))))
   1.185 +   
   1.186 +  ;;  Returns: 
   1.187 +  ;;   | Elapsed time: 5000.66214 msecs
   1.188 +  ;;  5"