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  • What is a good method to use with multithreading to simulate this?

    - by user1504257
    I am writing a program in c++ in visual studio to be able to handle a line at a park. I have all of my customers in a line at the park and I want to be able to service them using multithreading with openmp. When I put the pragma and such in, I have multiple threads servicing the same customer at the same time for each and every customer I create, not what I want. I want for example, if I had two threads and four customers, that thread one to do customer one while thread 2 does customer 2. Then I would like thread 1 to do customer 3 and thread 2 customer 4 at the same time. I don't know if its possible or if there is a better way, but I need to use openmp. Thanks for your input.

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  • NSAutoreleasePool carrying across methods?

    - by Tim
    I'm building an iPhone application where I detach some threads to do long-running work in the background so as not to hang the UI. I understand that threads need NSAutoreleasePool instances for memory management. What I'm not sure about is if the threaded method calls another method - does that method also need an NSAutoreleasePool? Example code: - (void)primaryMethod { [self performSelectorInBackground:@selector(threadedMethod) withObject:nil]; } - (void)threadedMethod { NSAutoreleasePool *aPool = [[NSAutoreleasePool alloc] init]; // Some code here [self anotherMethod]; // Maybe more code here [aPool drain]; } - (void)anotherMethod { // More code here } The reason I ask is I'm receiving errors that objects are being autoreleased with no pool in place, and are "just leaking." I've seen other questions where people didn't have autorelease pools in place at all, and I understand why an autorelease pool is needed. I'm specifically interested in finding out whether an autorelease pool created in (in this example) threadedMethod applies to objects created in anotherMethod.

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  • Can you have too many Delegate.BeginInvoke calls at once?

    - by stewsha
    I am cleaning up some old code converting it to work asynchronously. psDelegate.GetStops decStops = psLoadRetrieve.GetLoadStopsByLoadID; var arStops = decStops.BeginInvoke(loadID, null, null); WaitHandle.WaitAll(new WaitHandle[] { arStops.AsyncWaitHandle }); var stops = decStops.EndInvoke(arStops); Above is a single example of what I am doing for asynchronous work. My plan is to have close to 20 different delegates running. All will call BeginInvoke and wait until they are all complete before calling EndInvoke. My question is will having so many delegates running cause problems? I understand that BeginInvoke uses the ThreadPool to do work and that has a limit of 25 threads. 20 is under that limit but it is very likely that other parts of the system could be using any number of threads from the ThreadPool as well. Thanks!

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  • Is ReaderWriterLockSlim.EnterUpgradeableReadLock() essentially the same as Monitor.Enter()?

    - by Neil Barnwell
    So I have a situation where I may have many, many reads and only the occasional write to a resource shared between multiple threads. A long time ago I read about ReaderWriterLock, and have read about ReaderWriterGate which attempts to mitigate the issue where many writes coming in trump reads and hurt performance. However, now I've become aware of ReaderWriterLockSlim... From the docs, I believe that there can only be one thread in "upgradeable mode" at any one time. In a situation where the only access I'm using is EnterUpgradeableReadLock() (which is appropriate for my scenario) then is there much difference to just sticking with lock(){}? Here's the excerpt: A thread that tries to enter upgradeable mode blocks if there is already a thread in upgradeable mode, if there are threads waiting to enter write mode, or if there is a single thread in write mode. Or, does the recursion policy make any difference to this?

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  • C++ threaded class design from non-threaded class

    - by macs
    I'm working on a library doing audio encoding/decoding. The encoder shall be able to use multiple cores (i.e. multiple threads, using boost library), if available. What i have right now is a class that performs all encoding-relevant operations. The next step i want to take is to make that class threaded. So i'm wondering how to do this. I thought about writing a thread-class, creating n threads for n cores and then calling the encoder with the appropriate arguments. But maybe this is an overkill and there is no need for another class, so i'm going to make use of the "user interface" for thread-creation. I hope there are any suggestions.

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  • Is there a technical way to speed up a general program above current PC speed limit?

    - by Maksee
    Let's imagine I developed a Windows console application implementing some algorithm calculating something. Let's say it doesn't use any threads, just straightforward linear approach with ifs, loops and so on. Is there any technical way to make if run it 100x times faster than on the most advanced current PC? For example one of the way would be to run it on a super computer that emulates i386 faster than any of the existing PCs. But in this case the question what computer and does it really have ability to emulate Windows. In other words, is there real examples of such approach? Although in general it looks useless, but if there is a way, one could develop some program on his general home computer and pay for running it much faster on some other hardware. I suppose that this question could be asked on superuser.com, but since there are possible specific with such things as assembler instructions or threads, I thought that stackoverflow.com is better

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  • Configurability for windows application built in C#

    - by Sam
    Hi, I am working on a windows application which is developed in C#. I am kinda new in windows world. I want to restrict number of parallel threads running for this application at a given point of time. This number can be changed by user on a beefier machine. What is the best way to do this configuration and how it can be achieved. I can think of following approaches. 1. Use ConfigurationManager to read the configuration value. If user exists more than N number of threads show a message and give option there to modify the value of N. 2. Use registery entry? Thanks in Advance! Sam

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  • Forum board example schema in YAML format - modify for Nested set?

    - by takeshin
    I have created a forum board app, based on YAML schema found in 'real world examples' of Doctrine Manual, which looks similar to this: --- Forum_Category: columns: root_category_id: integer(10) parent_category_id: integer(10) name: string(50) description: string(99999) relations: Subcategory: class: Forum_Category local: parent_category_id foreign: id Rootcategory: class: Forum_Category local: root_category_id foreign: id Forum_Board: columns: category_id: integer(10) name: string(100) description: string(5000) relations: Category: class: Forum_Category local: category_id foreign: id Threads: class: Forum_Thread local: id foreign: board_id Forum_Entry: columns: author: string(50) topic: string(100) message: string(99999) parent_entry_id: integer(10) thread_id: integer(10) date: integer(10) relations: Parent: class: Forum_Entry local: parent_entry_id foreign: id Thread: class: Forum_Thread local: thread_id foreign: id Forum_Thread: columns: board_id: integer(10) updated: integer(10) closed: integer(1) relations: Board: class: Forum_Board local: board_id foreign: id Entries: class: Forum_Entry local: id foreign: thread_id How to modify this schema, to use NestedSet (Tree structure of threads and entries)?

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  • Java Application/Thread Server

    - by Manrico Corazzi
    I am looking for something very close to an application server with these features: it should handle a series of threads/daemons, allowing the user to start-stop-reload each one without affecting the others it should keep libraries separated between different threads/daemons it should allow to share some libraries Currently we have some legacy code reinventing the wheel... and not a perflectly round-shaped one at that! I thought to use Tomcat, but I don't need a web server, except maybe for the simple backoffice user interface (/manager/html). Any suggestion? Is there a non-web application server, or is there a better alternative to Tomcat (more lightweight, for example, or easier to configure)? Thanks in advance.

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  • Issue accessing class variable from thread.

    - by James
    Hello, The code below is meant to take an arraylist of product objects as an input, spun thread for each product(and add the product to the arraylist 'products'), check product image(product.imageURL) availability, remove the products without images(remove the product from the arraylist 'products'), and return an arraylist of products with image available. package com.catgen.thread; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import com.catgen.Product; import com.catgen.Utils; public class ProductFilterThread extends Thread{ private Product product; private List<Product> products = new ArrayList<Product>(); public ProductFilterThread(){ } public ProductFilterThread(Product product){ this.product = product; } public synchronized void addProduct(Product product){ System.out.println("Before add: "+getProducts().size()); getProducts().add(product); System.out.println("After add: "+getProducts().size()); } public synchronized void removeProduct(Product product){ System.out.println("Before rem: "+getProducts().size()); getProducts().remove(product); System.out.println("After rem: "+getProducts().size()); } public synchronized List<Product> getProducts(){ return this.products; } public synchronized void setProducts(List<Product> products){ this.products = products; } public void run(){ boolean imageExists = Utils.fileExists(this.product.ImageURL); if(!imageExists){ System.out.println(this.product.ImageURL); removeProduct(this.product); } } public List<Product> getProductsWithImageOnly(List<Product> products){ ProductFilterThread pft = null; try{ List<ProductFilterThread> threads = new ArrayList<ProductFilterThread>(); for(Product product: products){ pft = new ProductFilterThread(product); addProduct(product); pft.start(); threads.add(pft); } Iterator<ProductFilterThread> threadsIter = threads.iterator(); while(threadsIter.hasNext()){ ProductFilterThread thread = threadsIter.next(); thread.join(); } }catch(Exception e){ e.printStackTrace(); } System.out.println("Total returned products = "+getProducts().size()); return getProducts(); } } Calling statement: displayProducts = new ProductFilterThread().getProductsWithImageOnly(displayProducts); Here, when addProduct(product) is called from within getProductsWithImageOnly(), getProducts() returns the list of products, but that's not the case(no products are returned) when the method removeProduct() is called by a thread, because of which the products without images are never removed. As a result, all the products are returned by the module whether or not the contained products have images. What can be the problem here? Thanks in advance. James.

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  • how to write silverlight threading function in another file or project

    - by Piyush
    I am using three tier architecture.I have SilverlightUI and UIController two projects.SilverlightUI contains only UI pages and controls while UIController contains all proxies of WCF services. Now I have created threads to update my controls dynamically and to do processing parallel.AS the requirement I want to define all functionality of threads in UIController projects.What should I do? Currenty what I am doing - private void Button_Click(object sender, RoutedEventArgs e) { StartThreads(); } private void StartThreads() { private Thread _thread1; _thread1 = new Thread(DoThread1); _thread1.Start(); } public static void DoThread1() { _data1.Dispatcher.BeginInvoke(delegate() { _data1.Text = _count1.ToString(); }); System.Threading.Thread.Sleep(1000); } I Want to write DoThread1() method in UIController project and call that function from here button_click()

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  • Can getAttribute() method of Tomcat ServletContext implementation be called without synchronization?

    - by oo_olo_oo
    I would like to read some parameters during servlet initializtion (in init() method), and store them among servlet context attributes (using getServletContext().setAttribute()). I would like to read these parameters later - during some request processing (using getServletContext().getAttribute()). So, the multiple threads could do this simultaneously. My question is if such an attempt is safe? Could I be sure that multi threaded calls to the getAttribute() don't mess up any internal state of the servlet context? Please take into account that I'm not going to call the setAttribute() anywhere besides the initialization. So, only calls to the getAttribute() are going to be done from multiple threads. But depending on the internal implementation, this also could be dangerous. So, any information about Tomcat's implementation would be appreciated.

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  • Unresponsive UI when using BeginInvoke

    - by Kazoom
    Bckground I have a networked application written in C#. my server program has a UI and several communication threads, that read from tcp sockets and display messages on controller UI. Communication with each client is done through a seprate thread. When i recieve some stream of messages from one client , the thread for that client writes on UI, which is a richtextbox on a Form. I call SetTextHelper(string text) method of the form. which looks like this private delegate void MyTextUpdateHandler(string text); public void SetTextHelper(string text) { BeginInvoke(new MyTextUpdateHandler(SetText), new object[] { text }); } public setText(string text) { richtext.Text= text; } Question - If i use BeginInvoke my UI is entirely unresponsive when i m writing large stream of data to UI - Invoke solves that problem, but i read that for multi threaded environment where many thereads are sharing same resource Invoke can lead to deadlocks I share the common ichtextbox between around 16 threads - What would be a good desing for my situation?

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  • CUDA small kernel 2d convolution - how to do it

    - by paulAl
    I've been experimenting with CUDA kernels for days to perform a fast 2D convolution between a 500x500 image (but I could also vary the dimensions) and a very small 2D kernel (a laplacian 2d kernel, so it's a 3x3 kernel.. too small to take a huge advantage with all the cuda threads). I created a CPU classic implementation (two for loops, as easy as you would think) and then I started creating CUDA kernels. After a few disappointing attempts to perform a faster convolution I ended up with this code: http://www.evl.uic.edu/sjames/cs525/final.html (see the Shared Memory section), it basically lets a 16x16 threads block load all the convolution data he needs in the shared memory and then performs the convolution. Nothing, the CPU is still a lot faster. I didn't try the FFT approach because the CUDA SDK states that it is efficient with large kernel sizes. Whether or not you read everything I wrote, my question is: how can I perform a fast 2D convolution between a relatively large image and a very small kernel (3x3) with CUDA?

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  • Does a static object within a function introduce a potential race condition?

    - by Jeremy Friesner
    I'm curious about the following code: class MyClass { public: MyClass() : _myArray(new int[1024]) {} ~MyClass() {delete [] _myArray;} private: int * _myArray; }; // This function may be called by different threads in an unsynchronized manner void MyFunction() { static const MyClass _myClassObject; [...] } Is there a possible race condition in the above code? Specifically, is the compiler likely to generate code equivalent to the following, "behind the scenes"? void MyFunction() { static bool _myClassObjectInitialized = false; if (_myClassObjectInitialized == false) { _myClassObjectInitialized = true; _myClassObject.MyClass(); // call constructor to set up object } [...] } ... in which case, if two threads were to call MyFunction() nearly-simultaneously, then _myArray might get allocated twice, causing a memory leak? Or is this handled correctly somehow?

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  • Multiple Producers Single Consumer Queue

    - by Talguy
    I am new to multithreading and have designed a program that receives data from two microcontroller measuring various temperatures (Ambient and Water) and draws the data to the screen. Right now the program is singly threaded and its performance SUCKS A BIG ONE. I get basic design approaches with multithreading but not well enough to create a thread to do a task but what I don't get is how to get threads to perform seperate task and place the data into a shared data pool. I figured that I need to make a queue that has one consumer and multiple producers (would like to use std::queue). I have seen some code on the gtkmm threading docs that show a single Con/Pro queue and they would lock the queue object produce data and signal the sleeping thread that it is finished then the producer would sleep. For what I need would I need to sleep a thread, would there be data conflicts if i didn't sleep any of the threads, and would sleeping a thread cause a data signifcant data delay (I need realtime data to be drawn 30 frames a sec) How would I go about coding such a queue using the gtkmm/glibmm library.

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  • Wait until user press enter in textbox in another form and return value

    - by ekapek
    Hello, I am new to C# and I'm trying to do sth like this: myList = list of 1000+ string values; 1.StartNewThreads(50); //50 is the numbers of new threads 2.DoSth1(next value from myList); 3.DoSth2(); 4. var value = { ShowNewImageForm(); //show only if not another ImageForm is displayed if another is show - wait WaitUntilUserPressEnterInTextBox(); ReturnValueFormTextbox(); } 5.DoSth3(); 6.StartNewThread(); For now I have: foreach(String s in myList ) { DoSth1(s); DoSth2(); DoSth3(); } And now I'm looking for ideas to points 1,3,6 Can You suggest me how to resolve this? How to start 50 threads How to get value from textbox in another form when user press enter

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  • handling activity destruction in multithreaded android app

    - by Jayesh
    Hi, I have a multithreded app where background threads are used to load data over network or from disk/db. Every once in a while user will perform some action e.g. fetch news over network, which will spawn a background AsyncTask, but for some reason user will quit the app (press back button so that activity gets destroyed). In most such scenarios, I make appropriate checks in the background thread after it returns from n/w i/o, so that it won't crash by accessing members of the activity that is destroyed by now. However some corner cases are left where crashes happen, because the background thread would access some member of activity that is now null. Do other Android developers have some generic/recommended framework to handle such scenarios? These are the times when I wish android would have guaranteed termination of all threads when activity destroys (in the same way that regular linux process cleans up when it's quit)... but I guess Android devs had good reasons for not exposing process lifetimes through the api.

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  • javascript singleton question

    - by Shawn
    I just read a few threads on the discussion of singleton design in javascript. I'm 100% new to the Design Pattern stuff but as I see since a Singleton by definition won't have the need to be instantiated, conceptually if it's not to be instantiated, in my opinion it doesn't have to be treated like conventional objects which are created from a blueprint(classes). So my wonder is why not just think of a singleton just as something statically available that is wrapped in some sort of scope and that should be all. From the threads I saw, most of them make a singleton though traditional javascript new function(){} followed by making a pseudo constructor. Well I just think an object literal is enough enough: var singleton = { dothis: function(){}, dothat: function(){} } right? Or anybody got better insights? [update] : Again my point is why don't people just use a simpler way to make singletons in javascript as I showed in the second snippet, if there's an absolute reason please tell me. I'm usually afraid of this kind of situation that I simplify things to much :D

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  • How to end a thread in java?

    - by beagleguy
    hi all, I have 2 pools of threads ioThreads = (ThreadPoolExecutor)Executors.newCachedThreadPool(); cpuThreads = (ThreadPoolExecutor)Executors.newFixedThreadPool(numCpus); I have a simple web crawler that I want to create an iothread, pass it a url, it will then fetch the url and pass the contents over to a cpuThread to be processed and the ioThread will then fetch another url, etc... At some point the IO thread will not have any new pages to crawl and I want to update my database that this session is complete. How can I best tell when the threads are all done processing and the program can be ended?

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  • Recognizing synchronization object hanging two 3rd party executables

    - by eran
    I'm using a 3rd party tool, which uses a 4th party plugin. Occasionally, the tool will hang when launched. Looking at the stack traces, I can see a few threads are waiting on WaitForSingleObject, and my bet is that they're blocking each other. Some of the threads start at the 3rt party tool, and some at the 4th party plugin. What I'd like to do is file the most detailed complaint to the 3rd party tool vendor, assuming it's its fault (I don't trust their local support to get those details themselves). For that, I'd like to: Find out what are the synchronization objects currently waited on Find out who has created those synchronization objects Tools currently at hand are VS2005, WinDbg and Process Explorer. OS is Window 7 64 bit. Any suggestions?

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