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  • How to use IObservable/IObserver with ConcurrentQueue or ConcurrentStack

    - by James Black
    I realized that when I am trying to process items in a concurrent queue using multiple threads while multiple threads can be putting items into it, the ideal solution would be to use the Reactive Extensions with the Concurrent data structures. My original question is at: http://stackoverflow.com/questions/2997797/while-using-concurrentqueue-trying-to-dequeue-while-looping-through-in-parallel/ So I am curious if there is any way to have a LINQ (or PLINQ) query that will continuously be dequeueing as items are put into it. I am trying to get this to work in a way where I can have n number of producers pushing into the queue and a limited number of threads to process, so I don't overload the database. If I could use Rx framework then I expect that I could just start it, and if 100 items are placed in within 100ms, then the 20 threads that are part of the PLINQ query would just process through the queue. There are three technologies I am trying to work together: Rx Framework (Reactive LINQ) PLING System.Collections.Concurrent structures

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  • How do I profile in DrScheme?

    - by kunjaan
    How Do I profile my functions using DrScheme? (require profile) (define (factorial n) (cond ((= n 1) 1) (else (* n (factorial (- n 1)))))) (profile factorial) The above code returns Profiling results ----------------- Total cpu time observed: 0ms (out of 0ms) Number of samples taken: 0 (once every 0ms) ==================================== Caller Idx Total Self Name+srcLocal% ms(pct) ms(pct) Callee ==================================== > I tried: - (profile (factorial 100)) - (profile factorial) (factorial 100) But it gives me the same result. What am I doing wrong?

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  • How to simply this logic/code?

    - by Tattat
    I want to write an apps that accepts user command. The user command is used in this format: command -parameter For example, the app can have "Copy", "Paste", "Delete" command I am thinking the program should work like this : public static void main(String args[]){ if(args[0].equalsIgnoreCase("COPY")){ //handle the copy command } else if(args[0].equalsIgnoreCase("PASTE")){ //handle the copy command }/** code skipped **/ } So, it works, but I think it will become more and more complex when I have more command in my program, also, it is different to read. Any ideas to simply the logic?

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  • How do you handle your "Project Manager"

    - by Vecdid
    I currently work for a company who recently has downsized. I do all in house work, client installs, builds,q.a, well basically all the in house work. My direct boss is VERY untechnical and lately I have found it VERY hard to deal with his lack of knowledge. The biggest issues I have had are as follows: I am on many deadlines at a time. I get stopped to put together a half fast quote as I cannot be late on the deadline, in the meantime, three support calls comes in, I give quote, time too much so they outsource it. I then I have to fix everything the vendor broke. I get asked, when an issue arrises, why is the issue occurring and explain in detail, yet that detail means absolutly nothing to him. All he cares about are deadlines, yet he is the one who schdules everything. "I am a programmer not a graphic designer, meaqns nothing to him" I was hired as a .NET programmer, yet they let a vendor choose wordpress for many sites(yeah I had to learn all about it quick) I guess I can go on and on, but has anyone had to deal with this type of project manager? What is some advice, other than finding another job. Thanks in advance, and I made this a wiki, so please don't close...

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  • How well do zippers perform in practice, and when should they be used?

    - by Rob
    I think that the zipper is a beautiful idea; it elegantly provides a way to walk a list or tree and make what appear to be local updates in a functional way. Asymptotically, the costs appear to be reasonable. But traversing the data structure requires memory allocation at each iteration, where a normal list or tree traversal is just pointer chasing. This seems expensive (please correct me if I am wrong). Are the costs prohibitive? And what under what circumstances would it be reasonable to use a zipper?

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  • how to use quad core CPU in application

    - by Mayank
    For using all the cores of a quad core processor what do I need to change in my code is it about adding support of multi threading or is it which is taken care by OS itself. I am having FreeBSD and language I am using is C++. I want to give complete CPU cycles to my application at least 90%.

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  • scripts on Cshell

    - by lego69
    hello, I've got some problem, I have list of data in the file: 053-37878 03828008 Moskovitch James 500 052-34363 01234567 Mendelson Kippi 450 053-32322 03828008 Jameson Shula 350 054-39238 03333333 Merden Moshe 300 is it possible rewrite this list in the same file (without using temporary file) but without last number thanks in advance for any help (I'm talking about C-Shell scripts)

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  • State Monad, why not a tuple?

    - by thr
    I've just wrapped my head around monads (at least I'd like to think I have) and more specifically the state monad, which some people that are way smarter then me figured out, so I'm probably way of with this question. Anyway, the state monad is usually implemented with a M<'a as something like this (F#): type State<'a, 'state> = State of ('state -> 'a * 'state) Now my question: Is there any reason why you couldn't use a tuple here? Other then the possible ambiguity between MonadA<'a, 'b> and MonadB<'a, 'b> which would both become the equivalent ('a * 'b) tuple. Edit: Added example for clarity type StateMonad() = member m.Return a = (fun s -> a, s) member m.Bind(x, f) = (fun s -> let a, s_ = x s in f a s_) let state = new StateMonad() let getState = (fun s -> s, s) let setState s = (fun _ -> (), s) let execute m s = m s |> fst

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  • Efficient algorithm to generate all solutions of a linear diophantine equation with ai=1

    - by Ben
    I am trying to generate all the solutions for the following equations for a given H. With H=4 : 1) ALL solutions for x_1 + x_2 + x_3 + x_4 =4 2) ALL solutions for x_1 + x_2 + x_3 = 4 3) ALL solutions for x_1 + x_2 = 4 4) ALL solutions for x_1 =4 For my problem, there are always 4 equations to solve (independently from the others). There are a total of 2^(H-1) solutions. For the previous one, here are the solutions : 1) 1 1 1 1 2) 1 1 2 and 1 2 1 and 2 1 1 3) 1 3 and 3 1 and 2 2 4) 4 Here is an R algorithm which solve the problem. library(gtools) H<-4 solutions<-NULL for(i in seq(H)) { res<-permutations(H-i+1,i,repeats.allowed=T) resum<-apply(res,1,sum) id<-which(resum==H) print(paste("solutions with ",i," variables",sep="")) print(res[id,]) } However, this algorithm makes more calculations than needed. I am sure it is possible to go faster. By that, I mean not generating the permutations for which the sums is H Any idea of a better algorithm for a given H ?

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  • Suggestions for a PHP programmer wanting to create a timer app for an internet cafe

    - by grokker
    Hi, I was asked by a friend to make a timer app for his small internet cafe. He wants to have timers on each client PCs. The timers indicate how much time has been spent by the customer. On the PC that he uses, there's another program that has the overview of all the timers and there's a button for each client PCs that allows him to blacken out the screen. It's not automatic hence the button. The problem is I haven't done any desktop apps before so that's why I'm asking you guys (the awesome people at SO) for suggestions/advice on what language/tool to use. A little info about me: I did Java but haven't tried Swing though. I know a bit about Python and Ruby too. I don't mind learning new languages as long as I get to finish or get a prototype up and running. He doesn't mind if I could show him a prototype, it's actually for me. It gives me satisfaction to see I'm progressing. I'm not planning on asking him to pay me for doing this. Whatever he gives me is fine. P.S. He's using Windows XP

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  • Using pthread to perform matrix multiplication

    - by shadyabhi
    I have both matrices containing only ones and each array has 500 rows and columns. So, the resulting matrix should be a matrix of all elements having value 500. But, I am getting res_mat[0][0]=5000. Even other elements are also 5000. Why? #include<stdio.h> #include<pthread.h> #include<unistd.h> #include<stdlib.h> #define ROWS 500 #define COLUMNS 500 #define N_THREADS 10 int mat1[ROWS][COLUMNS],mat2[ROWS][COLUMNS],res_mat[ROWS][COLUMNS]; void *mult_thread(void *t) { /*This function calculates 50 ROWS of the matrix*/ int starting_row; starting_row = *((int *)t); starting_row = 50 * starting_row; int i,j,k; for (i = starting_row;i<starting_row+50;i++) for (j=0;j<COLUMNS;j++) for (k=0;k<ROWS;k++) res_mat[i][j] += (mat1[i][k] * mat2[k][j]); return; } void fill_matrix(int mat[ROWS][COLUMNS]) { int i,j; for(i=0;i<ROWS;i++) for(j=0;j<COLUMNS;j++) mat[i][j] = 1; } int main() { int n_threads = 10; //10 threads created bcos we have 500 rows and one thread calculates 50 rows int j=0; pthread_t p[n_threads]; fill_matrix(mat1); fill_matrix(mat2); for (j=0;j<10;j++) pthread_create(&p[j],NULL,mult_thread,&j); for (j=0;j<10;j++) pthread_join(p[j],NULL); printf("%d\n",res_mat[0][0]); return 0; }

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  • Is there a Java equivalent to libevent?

    - by JoelPM
    I've written a high-throughput server that handles each request in its own thread. For requests coming in it is occasionally necessary to do RPCs to one or more back-ends. These back-end RPCs are handled by a separate queue and thread-pool, which provides some bounding on the number of threads created and the maximum number of connections to the back-end (it does some caching to reuse clients and save the overhead of constantly creating connections). Having done all this, though, I'm beginning to think an event-based architecture would be more efficient. In searching around I haven't found any equivalents to libevent for Java, but maybe I'm not looking in the right place? Mina-statemachine from Apache was the closest thing I found, but it looks more verbose than I need and there's no real release available. Any suggestions?

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  • How much of the "Objective-C" I'm learning is universal Objective-C, and not Apple's frameworks?

    - by Chris Cooper
    This question is related to one of my others about C: What can you do in C without “std” includes? Are they part of “C,” or just libraries? I've become curious lately as to what is really contained the the core Objective-C language, and what parts of the Objective-C I've done for iPhone/OS X development is specific to Apple platforms. I know that things like syntax are the same, but for instance, is NSObject and its torrent of NS-subclasses actually part of "standard" Objective-C? Could I use them in, say, Windows? What parts are universal for the most part, and what parts would I only find on an Apple platform? If you want, giving an example of Objective-C used elsewhere as an example of what is more "universal" would help me as well. Thanks! =)

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  • What benefits does IOC provide over soft-coding?

    - by dotnetdev
    Take the following article for example: http://weblogs.asp.net/psteele/archive/2009/11/23/use-dependency-injection-to-simplify-application-settings.aspx?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+dotnetmvp+%28Patrick+Steele%27s+.NET+Blog%29 I don't see what benefit there is from the IOC approach as opposed to the traditional soft-coding approach. Can someone tell me what I am missing? Thanks

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  • How to return the output of a recursive function in Clojure

    - by Silanglaya Valerio
    Hi everyone! I'm new to functional languages and clojure, so please bear with me... I'm trying to construct a list of functions, with either random parameters or constants. The function that constructs the list of functions is already working, though it doesn't return the function itself. I verified this using println. Here is the snippet: (def operations (list #(- %1 %2) #(+ %1 %2) #(* %1 %2) #(/ %1 %2))) (def parameters (list \u \v \w \x \y \z)) (def parameterlistcount 6) (def paramcount 2) (def opcount 4) (defn generateFunction "Generates a random function list" ([] (generateFunction 2 4 0.5 0.6 '())) ([pc maxdepth fp pp function] (if (and (> maxdepth 0) (< (rand) fp)) (dotimes [i 2] (println(conj (generateFunction pc (dec maxdepth) fp pp function) {:op (nth operations (rand-int opcount))}))) (if (and (< (rand) pp) (> pc 0)) (do (dec pc) (conj function {:param (nth parameters (rand-int parameterlistcount))})) (conj function {:const (rand-int 100)}))))) Any help will be appreciated, thanks!

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  • Derivative of a Higher-Order Function

    - by Claudiu
    This is in the context of Automatic Differentiation - what would such a system do with a function like map, or filter - or even one of the SKI Combinators? Example: I have the following function: def func(x): return sum(map(lambda a: a**x, range(20))) What would its derivative be? What will an AD system yield as a result? (This function is well-defined on real-number inputs).

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