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• Pylons error "No object (name: request) has been registered for this thread" with debug = false

  - by Evgeny

  I'm unable to access the request object in my Pylons 0.9.7 controller when I set debug = false in the .ini file. I have the following code: def run_something(self): print('!!! request = %r' % request) print('!!! request.params = %r' % request.params) yield 'Stuff' With debugging enabled this works fine and prints out: !!! request = <Request at 0x9571190 POST http://my_url> !!! request.params = UnicodeMultiDict([... lots of stuff ...]) If I set debug = false I get the following: !!! request = <paste.registry.StackedObjectProxy object at 0x4093790> Error - <type 'exceptions.TypeError'>: No object (name: request) has been registered for this thread The stack trace confirms that the error is on the print('!!! request.params = %r' % request.params) line. I'm running it using the Paste server and these two lines are the very first lines in my controller method. This only occurs if I have yield statements in the method (even though the statements aren't reached). I'm guessing Pylons sees that it's a generator method and runs it on some other thread. My questions are: How do I make it work with debug = false ? Why does it work with debug = true ? Obviously this is quite a dangerous bug, since I normally develop with debug = true, so it can go unnoticed during development.

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• multi thread apps crashes in release mode

  - by etzarfat

  Hello, I'm using Visual Studio 2008 (programming in c). I've a weird problem I worte a program that has 2 threads that runs simultaneously, a recording thread (using audio card to record into memory) and a translation thread (using a speech engine to recognize the words). when I run my program in debug mode (aka setting a breakpoint in the code) it runs great, however when I run in debug mode or release mode (outside the visual studio enviroment) it crashes and give me the following exception: "Unhandled exception at 0x7c911129 in LowLevel.exe: 0xC0000005: Access violation reading location 0x014c7245." My stack looks: LowLevel.exe!__set_flsgetvalue() Line 256 + 0xc bytes C LowLevel.exe!_isleadbyte_l(int c=4359676, localeinfo_struct * plocinfo=0x00000001) Line 57 C++ 014b00d8() LowLevel.exe!PlayDateOfExam(int option=1) Line 2240 + 0x7 bytes C++ LowLevel.exe!NSCThread(void * arg=0x00000000) Line 1585 + 0xb bytes C++ kernel32.dll!7c80b729() winmm.dll!76b5b294() I uses the following file in my project "nsc.lib" and WinMM.lib" I'm not really familiar with threads I used a sample (which works great) and built on it. I saw a similiar question year on the forum but I didn't really understand the answers since I'm not familiar with with threads. Can someone help me? Thanks

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• Entity Framework lazy loading doesn't work from other thread

  - by Thomas Levesque

  Hi, I just found out that lazy loading in Entity Framework only works from the thread that created the ObjectContext. To illustrate the problem, I did a simple test, with a simple model containing just 2 entities : Person and Address. Here's the code : private static void TestSingleThread() { using (var context = new TestDBContext()) { foreach (var p in context.Person) { Console.WriteLine("{0} lives in {1}.", p.Name, p.Address.City); } } } private static void TestMultiThread() { using (var context = new TestDBContext()) { foreach (var p in context.Person) { Person p2 = p; // to avoid capturing the loop variable ThreadPool.QueueUserWorkItem( arg => { Console.WriteLine("{0} lives in {1}.", p2.Name, p2.Address.City); }); } } } The TestSingleThread method works fine, the Address property is lazily loaded. But in TestMultiThread, I get a NullReferenceException on p2.Address.City, because p2.Address is null. It that a bug ? Is this the way it's supposed to work ? If so, is there any documentation mentioning it ? I couldn't find anything on the subject on MSDN or Google... And more importantly, is there a workaround ? (other than explicitly calling LoadProperty from the worker thread...) Any help would be very appreciated PS: I'm using VS2010, so it's EF 4.0. I don't know if it was the same in the previous version of EF...

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• iPhone SDK background thread image loading problem

  - by retailevolved

  I have created a grid view that displays six "cells" of content. In each cell, an image is loaded from the web. There are a multiple pages of this grid (the user moves through them by swiping up / down to see the next set of cells). Each cell has its own view controller. When these view controllers load, they use an ImageLoader class that I made to load and display an image. These view controllers implement an ImageLoaderDelegate that has a single method that gets called when the image is finished loading. ImageLoader does its work on a background thread and then simply notifies its delegate when it is done loading, passing the image to the delegate method. Trouble is that if the user moves on to the next page of grid content before the image has finished loading (releasing the GridCellViewControllers that use the ImageLoaders), the app crashes. I suspect that this is because along the line, an asynchronous method finishes and attempts to notify its delegate but can't because it's been released. Here's some code to give a better picture: GridCellViewController.m: - (void)viewDidLoad { [super viewDidLoad]; // ImageLoader _loader = [[ProductImageLoader alloc] init]; _loader.delegate = self; if(_boundObject) [_loader loadImageForProduct:_boundObject]; } //ImageLoaderDelegate method - (void) imageDidFinishLoading: (UIImage *)image { [_imgController setImage:image]; } ProductImageLoader.m - (void) loadImageForProduct: (Product *) product { // Get image on another thread [NSThread detachNewThreadSelector:@selector(getImageForProductInBackground:) toTarget:self withObject:product]; } - (void) getImageForProductInBackground: (Product *) product { NSAutoreleasePool *tempPool = [[NSAutoreleasePool alloc] init]; HttpRequestLoader *tempLoader = [[HttpRequestLoader alloc] init]; NSURL *tempUrl = [product getImageUrl]; NSData *imageData = tempUrl ? [tempLoader loadSynchronousDataFromAddress:[tempUrl absoluteString]] : nil; UIImage *image = [[UIImage alloc] initWithData:imageData]; [tempPool release]; if(delegate) [delegate imageDidFinishLoading:image]; } The app crashes with EXC_BAD_ACCESS. Disclaimer: The code has been slightly modified to focus on the issue at hand.

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• Thread implemented as a Singleton

  - by rocknroll

  Hi all, I have a commercial application made with C,C++/Qt on Linux platform. The app collects data from different sensors and displays them on GUI. Each of the protocol for interfacing with sensors is implemented using singleton pattern and threads from Qt QThreads class. All the protocols except one work fine. Each protocol's run function for thread has following structure: void <ProtocolClassName>::run() { while(!mStop) //check whether screen is closed or not { mutex.lock() while(!waitcondition.wait(&mutex,5)) { if(mStop) return; } //Code for receiving and processing incoming data mutex.unlock(); } //end while } Hierarchy of GUI. 1.Login screen. 2. Screen of action. When a user logs in from login screen, we enter the action screen where all data is displayed and all the thread's for different sensors start. They wait on mStop variable in idle time and when data arrives they jump to receiving and processing data. Incoming data for the problem protocol is 117 bytes. In the main GUI threads there are timers which when timeout, grab the running instance of protocol using <ProtocolName>::instance() function Check the update variable of singleton class if its true and display the data. When the data display is done they reset the update variable in singleton class to false. The problematic protocol has the update time of 1 sec, which is also the frame rate of protocol. When I comment out the display function it runs fine. But when display is activated the application hangs consistently after 6-7 hours. I have asked this question on many forums but haven't received any worthwhile suggestions. I Hope that here I will get some help. Also, I have read a lot of literature on Singleton, multithreading, and found that people always discourage the use of singletons especially in C++. But in my application I can think of no other design for implementation. Thanks in advance A Hapless programmer

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• Using Qt signals/slots instead of a worker thread

  - by Rob

  I am using Qt and wish to write a class that will perform some network-type operations, similar to FTP/HTTP. The class needs to connect to lots of machines, one after the other but I need the applications UI to stay (relatively) responsive during this process, so the user can cancel the operation, exit the application, etc. My first thought was to use a separate thread for network stuff but the built-in Qt FTP/HTTP (and other) classes apparently avoid using threads and instead rely on signals and slots. So, I'd like to do something similar and was hoping I could do something like this: class Foo : public QObject { Q_OBJECT public: void start(); signals: void next(); private slots: void nextJob(); }; void Foo::start() { ... connect(this, SIGNAL(next()), this, SLOT(nextJob())); emit next(); } void Foo::nextJob() { // Process next 'chunk' if (workLeftToDo) { emit next(); } } void Bar::StartOperation() { Foo* foo = new Foo; foo->start(); } However, this doesn't work and UI freezes until all operations have completed. I was hoping that emitting signals wouldn't actually call the slots immediately but would somehow be queued up by Qt, allowing the main UI to still operate. So what do I need to do in order to make this work? How does Qt achieve this with the multitude of built-in classes that appear to perform lengthy tasks on a single thread?

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• Calling QAxWidget method outside of the GUI thread

  - by user304361

  I'm beginning to wonder if this is impossible, but I thought I'd ask in case there's a clever way to get around the problems I'm having. I have a Qt application that uses an ActiveX control. The control is held by a QAxWidget, and the QAxWidget itself is contained within another QWidget (I needed to add additional signals/slots to the widget, and I couldn't just subclass QAxWidget because the class doesn't permit that). When I need to interact with the ActiveX control, I call a method of the QWidget, which in turn calls the dynamicCall method of the QAxWidget in order to invoke the appropriate method of the ActiveX control. All of that is working fine. However, one method of the ActiveX control takes several seconds to return. When I call this method, my entire GUI locks up for a few seconds until the method returns. This is undesirable. I'd like the ActiveX control to go off and do its processing by itself and come back to me when it's done without locking up the Qt GUI. I've tried a few things without success: Creating a new QThread and calling QAxWidget::dynamicCall from the new thread Connecting a signal to the appropriate slot method of the QAxWidget and calling the method using signals/slots instead of using dynamicCall Calling QAxWidget::dynamicCall using QtConcurrent::run Nothing seems to affect the behavior. No matter how or where I use dynamicCall (or trigger the appropriate slot of the QAxWidget), the GUI locks until the ActiveX control completes its operation. Is there any way to detach this ActiveX processing from the Qt GUI thread so that the GUI doesn't lock up while the ActiveX control is running a method? Is there something clever I can do with QAxBase or QAxObject to get my desired results?

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• How do I find out what process Id and thread id / name has a file open

  - by peter

  Hi All, I am using C# in an application and am having some problems with a file becoming locked. The piece of code does this, while (true) { Read a packet from a socket (with data in it to add to the file) Open a file Writes data to it Close a file } But in the process the file becomes locked. I don't really understand how, we are are definately catching and reporting exceptions so I don't see how the file doesn't get closed every time. My best guess is that something else is opening the file, but I want to prove it. Can someone please provide a piece of code to check whether the file is open and if so report what processid and threadid has the file open. For example if I had this code, StreamWriter streamWriter1 = new StreamWriter(@"c:\logs\test.txt"); streamWriter1.WriteLine("Test"); // code to check for locks?? StreamWriter streamWriter2 = new StreamWriter(@"c:\logs\test.txt"); streamWriter1.Close(); streamWriter2.Close(); That will throw an exception because the file is locked when we try and open it the second time. So where the comment is what could I put in there to report that the current app (process Id) and the current thread (thread Id) have the file locked? Thanks.

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• Returning objects from another thread?

  - by Mark

  Trying to follow the hints laid out here, but she doesn't mention how to handle it when your collection needs to return a value, like so: private delegate TValue DequeueHandler(); public virtual TValue Dequeue() { if (dispatcher.CheckAccess()) { --count; var pair = dict.First(); var queue = pair.Value; var val = queue.Dequeue(); if (queue.Count == 0) dict.Remove(pair.Key); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, val)); return val; } else { dispatcher.BeginInvoke(new DequeueHandler(Dequeue)); } } This obviously won't work, because dispatcher.BeginInvoke doesn't return anything. What am I supposed to do? Or maybe I could replace dequeue with two functions, Peek and Pop, where Peek doesn't really need to be on the UI thread because it doesn't modify anything, right? As a side question, these methods don't need to be "locked" either, do they? If they're all forced to run in the UI thread, then there shouldn't be any concurrency issues, right?

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• Thread management advice - Is TPL a good idea?

  - by Ian

  I'm hoping to get some advice on the use of thread managment and hopefully the task parallel library, because I'm not sure I've been going down the correct route. Probably best is that I give an outline of what I'm trying to do. Given a Problem I need to generate a Solution using a heuristic based algorithm. I start of by calculating a base solution, this operation I don't think can be parallelised so we don't need to worry about. Once the inital solution has been generated, I want to trigger n threads, which attempt to find a better solution. These threads need to do a couple of things: They need to be initalized with a different 'optimization metric'. In other words they are attempting to optimize different things, with a precedence level set within code. This means they all run slightly different calculation engines. I'm not sure if I can do this with the TPL.. If one of the threads finds a better solution that the currently best known solution (which needs to be shared across all threads) then it needs to update the best solution, and force a number of other threads to restart (again this depends on precedence levels of the optimization metrics). I may also wish to combine certain calculations across threads (e.g. keep a union of probabilities for a certain approach to the problem). This is probably more optional though. The whole system needs to be thread safe obviously and I want it to be running as fast as possible. I tried quite an implementation that involved managing my own threads and shutting them down etc, but it started getting quite complicated, and I'm now wondering if the TPL might be better. I'm wondering if anyone can offer any general guidance? Thanks...

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• Measuring time spent in application / thread

  - by Adamski

  I am writing a simulation in Java whereby objects act under Newtonian physics. An object may have a force applied to it and the resulting velocity causes it to move across the screen. The nature of the simulation means that objects move in discrete steps depending on the time ellapsed between the current and previous iteration of the animation loop; e.g public void animationLoop() { long prev = System.currentTimeMillis(); long now; while(true) { long now = System.currentTimeMillis(); long deltaMillis = now - prev; prev = now; if (deltaMillis > 0) { // Some time has passed for (Mass m : masses) { m.updatePosition(deltaMillis); } // Do all repaints. } } } A problem arises if the animation thread is delayed in some way causing a large amount of time to ellapse (the classic case being under Windows whereby clicking and holding on minimise / maximise prevents a repaint), which causes objects to move at an alarming rate. My question: Is there a way to determine the time spent in the animation thread rather than the wallclock time, or can anyone suggest a workaround to avoid this problem? My only thought so far is to contstrain deltaMillis by some upper bound.

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• Best way to implement game loop without freezing UI thread

  - by Matt H

  I'm trying to make a simple 2D game in Java. So far I have a JFrame, with a menubar, and a class which extends JPanel and overrides it's paint method. Now, I need to get a game loop going, where I will update the position of images and so on. However, I'm stuck at how best to achieve this. Should I use multi-threading, because surely, if you put an infinite loop on the main thread, the UI (and thus my menu bar) will freeze up? Here's my code so far: import java.awt.Color; import java.awt.Graphics; import javax.swing.JPanel; @SuppressWarnings("serial") public class GameCanvas extends JPanel { public void paint(Graphics g) { while (true) { g.setColor(Color.DARK_GRAY); try { Thread.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } } } } import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; @SuppressWarnings("serial") public class Main extends JFrame { GameCanvas canvas = new GameCanvas(); final int FRAME_HEIGHT = 400; final int FRAME_WIDTH = 400; public static void main(String args[]) { new Main(); } public Main() { super("Game"); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); JMenuItem startMenuItem = new JMenuItem("Pause"); menuBar.add(fileMenu); fileMenu.add(startMenuItem); super.add(canvas); super.setVisible(true); super.setSize(FRAME_WIDTH, FRAME_WIDTH); super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); super.setJMenuBar(menuBar); } } Any pointers/tips? Also, where should I put my loop? In my main class, or my GameCanvas class? Any help is appreciated, thanks.

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• Static Logger in seperate thread?

  - by SirLenz0rlot

  Hi all, I've made my Logger, that logs a string, a static class with a static so I can call it from my entire project without having to make an instance of it. quite nice, but I want to make it run in a seperate thread, since accessing the file costs time is that possible somehow and what's the best way to do it? Its a bit of a short discription, but I hope the idea is clear. if not, please let me know. Thanks in advance! btw: any other improvements on my code are welcome as well, i have the feeling not everthing is as efficient as it can be: internal static class MainLogger { internal static void LogStringToFile(string logText) { DateTime timestamp = DateTime.Now; string str = timestamp.ToString("dd-MM-yy HH:mm:ss ", CultureInfo.InvariantCulture) + "\t" + logText + "\n"; const string filename = Constants.LOG_FILENAME; FileInfo fileInfo = new FileInfo(filename); if (fileInfo.Exists) { if (fileInfo.Length > Constants.LOG_FILESIZE) { File.Create(filename).Dispose(); } } else { File.Create(filename).Dispose(); } int i = 0; while(true) { try { using (StreamWriter writer = File.AppendText(filename)) { writer.WriteLine(str); } break; } catch (IOException) { Thread.Sleep(10); i++; if (i >= 8) { throw new IOException("Log file \"" + Constants.LOG_FILENAME + "\" not accessible after 5 tries"); } } } } } enter code here

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• WP7 BarcodeManager - Invalid cross-thread access

  - by rpf

  I'm trying to use Windows Phone 7 Silverlight ZXing Barcode Scanning Library but I'm having some problems. I'm using a background worker to check the image, but when I do this: WP7BarcodeManager.ScanBarcode(this.Image, BarcodeResults_Finished); The code throws an exception: Invalid cross-thread access. Here is my code... void photoChooserTask_Completed(object sender, PhotoResult e) { if (e.TaskResult == TaskResult.OK) { ShowImage(); System.Windows.Media.Imaging.BitmapImage bmp = new System.Windows.Media.Imaging.BitmapImage(); bmp.SetSource(e.ChosenPhoto); imgCapture.Source = bmp; this.Image = new BitmapImage(); this.Image.SetSource(e.ChosenPhoto); progressBar.Visibility = System.Windows.Visibility.Visible; txtStatus.Visibility = System.Windows.Visibility.Collapsed; worker.RunWorkerAsync(); } else ShowMain(); } void worker_DoWork(object sender, DoWorkEventArgs e) { try { Thread.Sleep(2000); WP7BarcodeManager.ScanMode = com.google.zxing.BarcodeFormat.UPC_EAN; WP7BarcodeManager.ScanBarcode(this.Image, BarcodeResults_Finished); } catch (Exception ex) { Debug.WriteLine("Error processing image.", ex); } } How can I solve this?

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• C#: Thread.CurrentThread.CurrentUICulture not working consistently

  - by xTRUMANx

  I've been working on a pet project on the weekends to learn more about C# and have encountered an odd problem when working with localization. To be more specific, the problem I have is with System.Threading.Thread.CurrentThread.CurrentUICulture. I've set up my app so that the user can quickly change the language of the app by clicking a menu item. The menu item in turn, saves the two-letter code for the language (e.g. "en", "fr", etc.) in a user setting called 'Language' and then restarts the application. Properties.Settings.Default.Language = "en"; Properties.Settings.Default.Save(); Application.Restart(); When the application is started up, the first line of code in the Form's constructor (even before InitializeComponent()) fetches the Language string from the settings and sets the CurrentUICulture like so: public Form1() { Thread.CurrentThread.CurrentUICulture = new CultureInfo(Properties.Settings.Default.Language); InitializeComponent(); } The thing is, this doesn't work consistently. Sometimes, all works well and the application loads the correct language based on the string saved in the settings file. Other times, it doesn't, and the language remains the same after the application is restarted. At first I thought that I didn't save the language before restarting the application but that is definitely not the case. When the correct language fails to load, if I were to close the application and run it again, the correct language would come up correctly. So this implies that the Language string has been saved but the CurrentUICulture assignment in my form constructor is having no effect sometimes. Any help? Is there something I'm missing of how threading works in C#? This could be machine-specific, so if it makes any difference I'm using Pentium Dual-Core CPU.

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• how to run TimerTask off main UI thread?

  - by huskyd97

  I am having trouble with a TimerTask Interfering with In App Purchasing (Async Tasks). I am weak with Threads, so I believe it is running on the main UI thread, eating up resources. How can I run this outside the UI thread? I have searched, and tried some suggestions using handlers. but seems like I get the same result, app gets really laggy. when I don't run this task (refreshes every 500mS), the activity runs smoothly, and there are no hangs during In app purchases. Your help is appreciated, code snippet below: public class DummyButtonClickerActivity extends Activity { protected Timer timeTicker = new Timer("Ticker"); private Handler timerHandler = new Handler(); protected int timeTickDown = 20; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.mainhd); // start money earned timer handler TimerTask tick = new TimerTask() { public void run() { myTickTask(); } }; timeTicker.scheduleAtFixedRate(tick, 0, 500); // 500 ms each } // End OnCreate protected void myTickTask() { if (timeTickDown == 0) { /// run my code here //total = total + _Rate; timerHandler.post(doUpdateTimeout); } else if(timeTickDown < 0) { // do nothing } timeTickDown--; } private Runnable doUpdateTimeout = new Runnable() { public void run() { updateTimeout(); } }; private void updateTimeout() { // reset tick timeTickDown = 2; // 2* 500ms == once a second } }

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• Threads syncronization with ThreadPoolExecutor

  - by justme1

  I'm trying to implement some logic when I create main(father) thread witch executes several other threads. Then it waits for some condition which child threads creates. After condition is meet the father executes some more child threads. The problem that when I use wait/notify I have java.lang.IllegalMonitorStateException exception. Here is the code: public class MyExecutor { final static ArrayBlockingQueue<Runnable> queue = new ArrayBlockingQueue<Runnable>(10); final static ExecutorService svc = Executors.newFixedThreadPool(1); static final ThreadPoolExecutor threadPool = new ThreadPoolExecutor(5, 8, 10, TimeUnit.SECONDS, queue); public static void main(String[] args) throws InterruptedException { final MyExecutor me = new MyExecutor(); svc.execute(new Runnable() { public void run() { try { System.out.println("Main Thread"); me.execute(threadPool, 1); System.out.println("Main Thread waiting"); wait(); System.out.println("Main Thread notified"); me.execute(threadPool, 2); Thread.sleep(100); threadPool.shutdown(); threadPool.awaitTermination(20000, TimeUnit.SECONDS); } catch (InterruptedException e) { e.printStackTrace(); } } }); svc.shutdown(); svc.awaitTermination(10000, TimeUnit.SECONDS); System.out.println("Main Thread finished"); } public void execute(ThreadPoolExecutor tpe, final int id) { tpe.execute(new Runnable() { public void run() { try { System.out.println("Child Thread " + id); Thread.sleep(2000); System.out.println("Child Thread " + id + " finished"); notify(); } catch (InterruptedException e) { e.printStackTrace(); } } }); } } When I comment wait and notify line I have the following output: Main Thread Main Thread waiting Main Thread notified Child Thread 1 Child Thread 2 Child Thread 1 finished Child Thread 2 finished Main Thread finished

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• Problem in thread pool implementation(C#3.0)

  - by Newbie

  Hi Experts, I have done the below thread pool program but the problem is that the WaitCallBackMethod(here ThreadPoolCallback) is getting called 2 times(which ideally should be called 1ce). what is the misktake I am making? public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion } I am using C#3.0 Thanks

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• No Hibernate Session bound to thread exception

  - by Benchik

  I have Hibernate 3.6.0.Final and Spring 3.0.0.RELEASE I get "No Hibernate Session bound to thread, and configuration does not allow creation of non-transactional one here" If I add the thread specification back in, I get "saveOrUpdate is not valid without active transaction" Any ideas? The spring-config.xml: <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName" value="org.hsqldb.jdbcDriver"/> <property name="url" value="jdbc:hsqldb:mem:jsf2demo"/> <property name="username" value="sa"/> <property name="password" value=""/> </bean> <bean id="sampleSessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"> <property name="dataSource" ref="sampleDataSource"/> <property name="annotatedClasses"> <list> <value>com.maxheapsize.jsf2demo.Book</value> </list> </property> <property name="hibernateProperties"> <props> <!-- prop key="hibernate.connection.pool_size">0</prop--> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.dialect">org.hibernate.dialect.HSQLDialect</prop> <!-- prop key="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</prop> <prop key="hibernate.current_session_context_class">thread</prop--> <prop key="hibernate.hbm2ddl.auto">create</prop> </props> </property> </bean> <bean id="sampleDataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName"> <value>org.hsqldb.jdbcDriver</value> </property> <property name="url"> <value> jdbc:hsqldb:file:/spring/db/springdb;SHUTDOWN=true </value> </property> <property name="username" value="sa"/> <property name="password" value=""/> </bean> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory" ref="sampleSessionFactory"/> </bean> <bean id="daoTxTemplate" abstract="true" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean"> <property name="transactionManager" ref="transactionManager"/> <property name="transactionAttributes"> <props> <prop key="create*"> PROPAGATION_REQUIRED,ISOLATION_READ_COMMITTED </prop> <prop key="get*"> PROPAGATION_REQUIRED,ISOLATION_READ_COMMITTED </prop> </props> </property> </bean> <bean name="openSessionInViewInterceptor" class="org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor"> <property name="sessionFactory" ref="sampleSessionFactory"/> <property name="singleSession" value="true"/> </bean> <bean id="nameDao" parent="daoTxTemplate"> <property name="target"> <bean class="com.maxheapsize.dao.NameDao"> <property name="sessionFactory" ref="sampleSessionFactory"/> </bean> </property> </bean> and the DAO: public class NameDao { private SessionFactory sessionFactory; public void setSessionFactory(SessionFactory sessionFactory) { this.sessionFactory = sessionFactory; } public SessionFactory getSessionFactory() { return sessionFactory; } @Transactional @SuppressWarnings("unchecked") public List<Name> getAll() { Session session = this.sessionFactory.getCurrentSession(); List<Name> names = (List<Name>)session.createQuery("from Name").list(); return names; } //@Transactional(propagation= Propagation.REQUIRED, readOnly=false) @Transactional public void save(Name name){ Session session = this.sessionFactory.getCurrentSession(); session.saveOrUpdate(name); session.flush(); } }

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• Simple Android Binary Text Clock

  - by Hristo

  Hello, I want to create a simple android binary clock but my application crashes. I use 6 textview fields: 3 for the decimal and 3 for the binary representation of the current time (HH:mm:ss). Here's the code: import java.text.SimpleDateFormat; import java.util.Calendar; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class Binary extends Activity implements Runnable { Thread runner; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); if (runner == null) { //start the song runner = new Thread(this); runner.start(); } } @Override public void run() { TextView hours_dec = (TextView) findViewById(R.id.hours_dec); TextView mins_dec = (TextView) findViewById(R.id.mins_dec); TextView secs_dec = (TextView) findViewById(R.id.secs_dec); TextView hours_bin = (TextView) findViewById(R.id.hours_bin); TextView mins_bin = (TextView) findViewById(R.id.mins_bin); TextView secs_bin = (TextView) findViewById(R.id.secs_bin); SimpleDateFormat hours_sdf = new SimpleDateFormat("HH"); SimpleDateFormat mins_sdf = new SimpleDateFormat("mm"); SimpleDateFormat secs_sdf = new SimpleDateFormat("ss"); Calendar cal = Calendar.getInstance(); while (runner != null) { WaitAMoment(); cal.getTime(); hours_dec.setText(hours_sdf.format(cal.getTime())); mins_dec.setText(mins_sdf.format(cal.getTime())); secs_dec.setText(secs_sdf.format(cal.getTime())); hours_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) hours_dec.getText())))); mins_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) mins_dec.getText())))); secs_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) secs_dec.getText())))); } } protected void WaitAMoment() { try { Thread.sleep(100); } catch (InterruptedException e) { }; } }`

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• How to make Stack.Pop threadsafe

  - by user260197

  I am using the BlockingQueue code posted in this question, but realized I needed to use a Stack instead of a Queue given how my program runs. I converted it to use a Stack and renamed the class as needed. For performance I removed locking in Push, since my producer code is single threaded. My problem is how can thread working on the (now) thread safe Stack know when it is empty. Even if I add another thread safe wrapper around Count that locks on the underlying collection like Push and Pop do, I still run into the race condition that access Count and then Pop are not atomic. Possible solutions as I see them (which is preferred and am I missing any that would work better?): Consumer threads catch the InvalidOperationException thrown by Pop(). Pop() return a nullptr when _stack-Count == 0, however C++-CLI does not have the default() operator ala C#. Pop() returns a boolean and uses an output parameter to return the popped element. Here is the code I am using right now: generic <typename T> public ref class ThreadSafeStack { public: ThreadSafeStack() { _stack = gcnew Collections::Generic::Stack<T>(); } public: void Push(T element) { _stack->Push(element); } T Pop(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Pop(); } finally { System::Threading::Monitor::Exit(_stack); } } public: property int Count { int get(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Count; } finally { System::Threading::Monitor::Exit(_stack); } } } private: Collections::Generic::Stack<T> ^_stack; };

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• proper use of volatile keyword

  - by luke

  I think i have a pretty good idea about the volatile keyword in java, but i'm thinking about re-factoring some code and i thought it would be a good idea to use it. i have a class that is basically working as a DB Cache. it holds a bunch of objects that it has read from a database, serves requests for those objects, and then occasionally refreshes the database (based on a timeout). Heres the skeleton public class Cache { private HashMap mappings =....; private long last_update_time; private void loadMappingsFromDB() { //.... } private void checkLoad() { if(System.currentTimeMillis() - last_update_time > TIMEOUT) loadMappingsFromDB(); } public Data get(ID id) { checkLoad(); //.. look it up } } So the concern is that loadMappingsFromDB could be a high latency operation and thats not acceptable, So initially i thought that i could spin up a thread on cache startup and then just have it sleep and then update the cache in the background. But then i would need to synchronize my class (or the map). and then i would just be trading an occasional big pause for making every cache access slower. Then i thought why not use volatile i could define the map reference as volatile private volatile HashMap mappings =....; and then in get (or anywhere else that uses the mappings variable) i would just make a local copy of the reference: public Data get(ID id) { HashMap local = mappings; //.. look it up using local } and then the background thread would just load into a temp table and then swap the references in the class HashMap tmp; //load tmp from DB mappings = tmp;//swap variables forcing write barrier Does this approach make sense? and is it actually thread-safe?

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• Reading same file from multiple threads in C#

  - by Gustavo Rubio

  Hi. I was googling for some advise about this and I found some links. The most obvious was this one but in the end what im wondering is how well my code is implemented. I have basically two classes. One is the Converter and the other is ConverterThread I create an instance of this Converter class that has a property ThreadNumber that tells me how many threads should be run at the same time (this is read from user) since this application will be used on multi-cpu systems (physically, like 8 cpu) so it is suppossed that this will speed up the import The Converter instance reads a file that can range from 100mb to 800mb and each line of this file is a tab-delimitted value record that is imported to another destination like a database. The ConverterThread class simply runs inside the thread (new Thread(ConverterThread.StartThread)) and has event notification so when its work is done it can notify the Converter class and then I can sum up the progress for all these threads and notify the user (in the GUI for example) about how many of these records have been imported and how many bytes have been read. It seems, however that I'm having some trouble because I get random errors about the file not being able to be read or that the sum of the progress (percentage) went above 100% which is not possible and I think that happens because threads are not being well managed and probably the information returned by the event is malformed (since it "travels" from one thread to another) Do you have any advise on better practices of implementation of threads so I can accomplish this? Thanks in advance.

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• Apply [ThreadStatic] attribute to a method in external assembly

  - by Sen Jacob

  Can I use an external assembly's static method like [ThreadStatic] method? Here is my situation. The assembly class (which I do not have access to its source) has this structure public class RegistrationManager() { private RegistrationManager() {} public static void RegisterConfiguration(int ID) {} public static object DoWork() {} public static void UnregisterConfiguration(int ID) {} } Once registered, I cannot call the DoWork() with a different ID without unregistering the previously registered one. Actually I want to call the DoWork() method with different IDs simultaneously with multi-threading. If the RegisterConfiguration(int ID) method was [ThreadStatic], I could have call it in different threads without problems with calls, right? So, can I apply the [ThreadStatic] attribute to this method or is there any other way I can call the two static methods same time without waiting for other thread to unregister it? If I check it like the following, it should work. for(int i=0; i < 10; i++) { new Thread(new ThreadStart(() => Checker(i))).Start(); } public string Checker(int i) { public static void RegisterConfiguration(i); // Now i cannot register second time public static object DoWork(i); Thread.Sleep(5000); // DoWork() may take a little while to complete before unregistered public static void UnregisterConfiguration(i); }

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• Cannot make a static reference to the non-static type MyRunnable

  - by kaiwii ho

  Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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