Re: map vs. pmap
Thanks. I looked at Java doc for random which says This method is properly synchronized to allow correct use by more than one thread. However, if many threads need to generate pseudorandom numbers at a great rate, it may reduce contention for each thread to have its own pseudorandom-number generator. art Returns: On Aug 27, 9:22 pm, Lee Spector lspec...@hampshire.edu wrote: On Aug 27, 2011, at 10:41 PM, Andy Fingerhut wrote: I suspect that (rand), which calls java.lang.Math.random(), is a synchronized method, meaning that if you try to call it from many parallel threads, even those on physically separate cores, will execute one at a time. Things could even take more time if you try to execute them in parallel than sequentially, due to lock contention overhead that does not occur if you try to execute them sequentially. http://download.oracle.com/javase/1.4.2/docs/api/java/lang/Math.html#... Try doing something besides (rand) in your function t that does not use locking or synchronized methods. You might also experiment with having no Thread/sleep call in there, but that might be part of what you are trying to learn the behavior of. I'm not sure. Or if you really want to be getting random numbers in all of those threads you could arrange for all of them to use thread-local Random objects -- created with something like (new java.util.Random) -- and then get your random numbers with something like (. thread-local-random-generator (nextFloat)). I did something similar in my project athttps://github.com/lspector/Clojushalthough there I use agents rather than pmap to initiate the concurrent processes. -Lee -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
Re: map vs. pmap
fixed it (defn t [m] (let [r (java.util.Random.)] (dotimes [i m] (. r nextDouble))) (Thread/sleep 1000)) (defn testmap [f n m] (time (doall (f t (repeat n m) user= (testmap map 8 200) Elapsed time: 8869.942784 msecs (nil nil nil nil nil nil nil nil) user= (testmap pmap 8 200) Elapsed time: 1178.490827 msecs (nil nil nil nil nil nil nil nil) thanks art -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
map vs. pmap
I understand that pmap needs to have big chunks to overcome the overhead but I don't understand my results (defn t [m] (dotimes [i m] (rand)) (Thread/sleep 1000)) (defn testmap [f n m] (time (doall (f t (repeat n m) user= (testmap map 8 100) Elapsed time: 8108.174484 msecs (nil nil nil nil nil nil nil nil) user= (testmap pmap 8 100) Elapsed time: 1006.797146 msecs (nil nil nil nil nil nil nil nil) user= (testmap pmap 8 100) Elapsed time: 3781.967909 msecs (nil nil nil nil nil nil nil nil) user= (testmap map 8 100) Elapsed time: 8544.896008 msecs (nil nil nil nil nil nil nil nil) user= (testmap map 8 1000) Elapsed time: 10663.057874 msecs (nil nil nil nil nil nil nil nil) user= (testmap pmap 8 1000) Elapsed time: 29525.579612 msecs (nil nil nil nil nil nil nil nil) I'm using an i7 with 8 processors so the Thread alone mostly gives an 8-fold speedup. Calling (rand) more times impacts pmap even though I map and pmap on a list of size 8 to spawn eight functions each with a lot of work. -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
Re: Clojure Speed performance test
Below is a Clojure solution that runs in 8.58 microseconds on my machine. I only did it for the 40, 3 case. Records are linked. The list reduction solution runs in 23.4 and the element recursion in 27.3 --art (defrecord Soldier [val r]) (def v (vec (map #(Soldier. % (inc %)) (range 40 (def v2 (assoc v 39 (Soldier. 39 0))) (defn move [v i] (let [r1 (v i) r2 (:r (v (:r r1)))] [(:r (v r2)) (assoc v (:r r1) (Soldier. (:val r1) (:r (v r2] )) (defn joe [v] (loop [v v i 0 count 39] (if (zero? count) (inc i) (let [[a b] (move v i)] (recur b a (dec count)) (prn (joe v2)) (let [start (System/currentTimeMillis) iterations 10] (doseq [i (range 10)] (joe v2)) (let [end (System/currentTimeMillis)] (println (/ (* (- end start) 1000.00) iterations) microseconds))) On Aug 18, 12:40 am, Roberto Mannai roberm...@gmail.com wrote: Hello, I recently stumbled upon this page:http://java.dzone.com/articles/contrasting-performance They are comparing several languages (Java, Scala, Python, Erlang, Clojure, Ruby, Groovy, Javascript), and Clojure rated very badly: Object Oriented List Reduction Element Recursion Java 1.6 0.637 1.435 2.816 Clojure 1.2.1 - 25.966 28.753 Maybe the clojure's scripts were not very idiomatic? If some guru wants to check them, here's the source code: -https://github.com/dnene/josephus/blob/master/element-recursion/josep... - https://github.com/dnene/josephus/blob/master/list-reduction/josephus... All the best, Roberto -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
Re: college courses
I'm going to start the Clojure unit in the senior class in a few weeks. They have done some F# and I will repeat the F# assignments in Clojure for comparison. They all have some Java and some C++ but the unit here is just some functional programming without Java interop so I don't think it matters. The grad class has been going well and I get some interesting programs. Here Java is handy for GUI so it does help to have some Java. On Oct 22, 1:57 am, Daniel Werner daniel.d.wer...@googlemail.com wrote: On Oct 19, 5:03 pm, artg artgittle...@gmail.com wrote: I'm using Programming Clojure in a grad course and doing a short Clojure unit in a senior programming languages course at Calif State Univ Long Beach. Art, what kind of pre-existing knowledge do you expect or require in your students? In your experience, do they need a background in Java to use Clojure effectively for real-world tasks? And how fast do they absorb Clojure's FP style, provided they haven't learned a functional language before? --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
Re: college courses
I'm using Programming Clojure in a grad course and doing a short Clojure unit in a senior programming languages course at Calif State Univ Long Beach. On Oct 19, 2:19 am, Andreas Wenger andi.xeno...@googlemail.com wrote: At the Technische Universität München (Germany), I know of two courses where Clojure was at least mentioned. This year there was an advanced Java seminar with one talk about Clojure (http://www2.in.tum.de/hp/Main?nid=59). Next year there is a programming models and code generation seminar with a talk about the concurrency features of Clojure (http://www.lrr.in.tum.de/public/HauptseminarCodegenerierungWS09- not mentioned yet). But I know of no lecture that uses Clojure as its main language (yet). In the second semester, our students are teached OCaml or a self- constructed functional-like Java when they learn functional programming. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
Re: Uncle Bob: bowling meets Clojure
What is group-frames?
--art
On Jul 21, 12:00 am, Mark Triggs mark.h.tri...@gmail.com wrote:
Hi Stu,
Stuart Halloway stuart.hallo...@gmail.com writes:
Uncle Bob Martin, a very well-respected OO and agile guy, is learning
Clojure. He has posted an example [1] and asked for feedback from the
Clojure community. I have made my suggestions in code [2] and will be
writing them up shortly.
Would love to see what other folks on this list have to say.
My first version came out rather similar to yours, and then I started
thinking about turning the problem on its head and making the concept of
types of rolls more explicit. I'm still not sure how I feel about
this, but the line of thinking led me to code like this:
(ns bowling-game
(:use clojure.contrib.seq-utils))
(def *roll-types*
[{:name strike
:satisfies #(= (first %) 10)
:consumes 3
:advances 1}
{:name spare
:satisfies #(= (apply + (take 2 %))
10)
:consumes 3
:advances 2}
{:name regular (underachieving?)
:satisfies (constantly true)
:consumes 2
:advances 2}])
(defn roll-type [rolls]
(find-first #((:satisfies %) rolls)
*roll-types*))
(defn frames [rolls]
(when (seq rolls)
(let [{:keys [consumes advances]} (roll-type rolls)]
(cons (take consumes rolls)
(frames (drop advances rolls))
(defn score-game [rolls]
(reduce + (map #(reduce + %)
(take 10 (group-frames rolls)
Cheers,
Mark
--
Mark Triggs
mark.h.tri...@gmail.com
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timing for map
user= (time (map answer '(50 50))) Elapsed time: 0.032826 msecs (392330 392711) user= (time (answer 50)) Elapsed time: 6357.131423 msecs 392849 When I try to time 'map' it seems to return right away. How do I time the full two executions of 'answer'? --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
