Mercurial > rlm
view src/rlm/function_utils.clj @ 3:c8e35134bf8e
working on qotd.
author | Robert McIntyre <rlm@mit.edu> |
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date | Wed, 18 Jan 2012 05:18:57 -0700 |
parents | 78a630e650d2 |
children | 12d1367cf1aa |
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1 ;; Various Operators on Pure Functions2 ;;3 ;; Open source Liscence and all that4 (ns5 rlm.function-utils6 "Collection of Operators on Pure Functions"7 {:author "Robert McIntyre"}8 (:use [clojure.contrib.profile]))10 (def void ::void)12 (comment14 "Please help me out here. I'm trying to make a higher order function that takes15 pure functions that are mathmaticaly the same but have different times and returns another16 function that runs them both and returns the resut of the one that finishes first."19 "here's a repl session:21 mobius> " (time (dotimes [_ 500]((mix-futures + +) 40 3 3 3 3 3))) "22 Elapsed time: 85.792995 msecs23 nil24 mobius> " (time (dotimes [_ 500](+ 40 3 3 3 3 3))) "25 Elapsed time: 6.956338 msecs26 nil27 mobius> " (time (dotimes [_ 500]((mix-threads + +) 40 3 3 3 3 3))) "28 Elapsed time: 706.227065 msecs29 nil32 mobius> " (defn fast-five [& args] 5) "33 #'mobius/fast-five35 mobius> " (defn slow-five [& args] (Thread/sleep 5000) (println "Oh YEAH!!!!") 5) "36 #'mobius/slow-five38 mobius> " (profile (time (dotimes [_ 5000] (thread-five)))) "39 \"Elapsed time: 12187.981587 msecs\"40 Name mean min max count sum41 create-atom 9621 2025 4433928 5000 4810683042 create-threads 5156 2724 2880268 5000 2578379643 kill-threads 91313 27866 11175718 5000 45656706644 loop 2124249 38482 18470781 5000 1062124989945 return 1242 838 5309 5000 621262646 start-threads 252985 110348 12272835 5000 126492795347 nil49 mobius> " (profile (time (dotimes [_ 5000] (future-five)))) "50 \"Elapsed time: 607.266671 msecs\"51 Name mean min max count sum52 create-atom 1472 1047 31708 5000 736313953 create-futures 30539 2514 1330660 5000 15269799854 kill-threads 54158 2444 3938833 5000 27079289755 loop 81117 8800 6083059 5000 40558751656 return 1215 838 618782 5000 607814657 nil61 What can I improve here, and why is the future version sooo much faster than the62 thread version? Is there a better way than using loop?63 "65 )68 (defn mix69 "Takes any number of mathematically equal functions with70 possibly different run-times and returns a function that71 runs each in a separate thread, returns the result from72 the first thread which finishes, and cancels the other threads."73 {:author "Robert McIntyre"}74 ([& functions]75 (fn [& args]76 (let [result (promise)77 futures (doall (for [fun functions]78 (future (deliver result (apply fun args)))))79 answer @result]80 (dorun (map future-cancel futures))81 answer))))83 (defn mix-pred84 "Takes any number of mathematically equal functions with85 possibly different run-times and returns a function that86 runs each in a separate thread, returns the result from87 the first thread which finishes, and cancels the other threads."88 {:author "Robert McIntyre"}89 ([pred & functions]90 (fn [& args]91 (let [result (promise)92 futures (doall (for [fun functions]93 (let [answer (apply fun args)]94 (if (pred answer)95 (future (deliver result (apply fun args)))))))96 answer @result]97 (dorun (map future-cancel futures))98 answer))))102 (defn mix-threads103 " Takes any number of pure functions that take the same arguments and104 compute the same value and returns a function that runs each in a separate105 thread, returns the result from the first thread which finshes, and cancels106 the other threads. Explicitly uses nasty Threads.108 For example:109 (do110 (defn fun1 [] (Thread/sleep 5000) 5)111 (defn fun2 [] (Thread/sleep 700000) 5)112 (time ((mix fun1 fun2))))114 Returns:115 | Elapsed time: 5000.66214 msecs116 5"117 [& functions]118 (fn [& args]119 (let [result (prof :create-atom (atom void))120 threads121 (prof :create-threads (map122 (fn [fun]123 (Thread.124 (fn []125 (try (let [answer (apply fun args)]126 (reset! result answer))127 (catch Exception _ nil)))))128 functions))]130 (prof :start-threads (dorun (map #(.start %) threads)))131 (prof :loop (loop []132 (if (= (deref result) void)133 (recur)134 (do (prof :kill-threads (dorun (map #(.stop %) threads)))135 (prof :return (deref result)))136 ))))))138 (defmacro defmix139 " Defines a function from any number of pure functions that take the same140 arguments and compute the same value which:142 Runs each in a separate thread.143 Returns the result from the first thread which finshes.144 Cancels the other threads.146 Use this whenever you want to combine two pure functions that147 compute the same thing, but use different algorithms with different148 run times for various inputs.150 For example:151 (do152 (defn fun1 [] (Thread/sleep 5000) 5)153 (defn fun2 [] (Thread/sleep 700000) 5)154 (defmix fun3 \"combination of fun1 and fun2\" fun1 fun2)155 (time (fun3))157 Returns:158 | Elapsed time: 5000.66214 msecs159 5"161 {:arglists '([name doc-string? functions*])}163 [name & functions]164 (let [doc-string (if (string? (first functions)) (first functions) "")165 functions (if (string? (first functions)) (rest functions) functions)166 arglists (:arglists (meta (resolve (eval `(quote ~(first functions))))))167 name (with-meta name (assoc (meta name) :arglists `(quote ~arglists) :doc doc-string))]168 `(def ~name (mix ~@functions))))171 (defn runonce172 "Decorator. returns a function which will run only once. Inspired173 by Halloway's version from lancet."174 {:author "Robert McIntyre"}175 [function]176 (let [sentinel (Object.)177 result (atom sentinel)]178 (fn [& args]179 (locking sentinel180 (if (= @result sentinel)181 (reset! result (apply function args))182 @result)))))186 ;I'm thinking this will be the docstring for mix eventually.188 ;; " Takes any number of pure functions that take the same arguments and189 ;; compute the same value and returns a function that runs each in a separate190 ;; thread, returns the result from the first thread which finshes, and cancels191 ;; the other threads.193 ;; For example:194 ;; (do195 ;; (defn fun1 [] (Thread/sleep 5000) 5)196 ;; (defn fun2 [] (Thread/sleep 700000) 5)197 ;; (time ((mix fun1 fun2))))199 ;; Returns:200 ;; | Elapsed time: 5000.66214 msecs201 ;; 5"