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  • Cache consistency & spawning a thread

    - by Dave Keck
    Background I've been reading through various books and articles to learn about processor caches, cache consistency, and memory barriers in the context of concurrent execution. So far though, I have been unable to determine whether a common coding practice of mine is safe in the strictest sense. Assumptions The following pseudo-code is executed on a two-processor machine: int sharedVar = 0; myThread() { print(sharedVar); } main() { sharedVar = 1; spawnThread(myThread); sleep(-1); } main() executes on processor 1 (P1), while myThread() executes on P2. Initially, sharedVar exists in the caches of both P1 and P2 with the initial value of 0 (due to some "warm-up code" that isn't shown above.) Question Strictly speaking – preferably without assuming any particular CPU – is myThread() guaranteed to print 1? With my newfound knowledge of processor caches, it seems entirely possible that at the time of the print() statement, P2 may not have received the invalidation request for sharedVar caused by P1's assignment in main(). Therefore, it seems possible that myThread() could print 0. References These are the related articles and books I've been reading. (It wouldn't allow me to format these as links because I'm a new user - sorry.) Shared Memory Consistency Models: A Tutorial hpl.hp.com/techreports/Compaq-DEC/WRL-95-7.pdf Memory Barriers: a Hardware View for Software Hackers rdrop.com/users/paulmck/scalability/paper/whymb.2009.04.05a.pdf Linux Kernel Memory Barriers kernel.org/doc/Documentation/memory-barriers.txt Computer Architecture: A Quantitative Approach amazon.com/Computer-Architecture-Quantitative-Approach-4th/dp/0123704901/ref=dp_ob_title_bk

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  • How to use thread in Django

    - by zomboid
    I want to check users' subscribed dates for certain period. And send mail to users whose subscription is finishing (ex. reminds two days). I think the best way is using thread and timer to check dates. But I have no idea how to call this function. I don't want to make a separate program or shell. I want to combine this procedure to my django code. I tried to call this function in my settings.py file. But it seems it is not a good idea. It calls the fucntion and creates thread everytime i imported settings.

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  • Thread vs ThreadPool - .Net 2.0

    - by NLV
    Hello I'm not able to understand the difference between Thread vs ThreadPool. Consider i've to manipulate 50,000 records using threads. In case of threads i need to either predefine no of threads or no of records per threads. Either of them has to be constant. In case of threadpool we dont need to set any of them theoretically. But practically we need to assign the number of records per thread, because the no of threads may grow extremely large if the input no of records is huge. Any insights on this?

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  • Adding row to DataGridView from Thread

    - by she hates me
    Hello, I would like to add rows to DataGridView from two seperate threads. I tried something with delegates and BeginInvoke but doesn't work. Here is my row updater function which is called from another function in a thread. public delegate void GRIDLOGDelegate(string ulke, string url, string ip = ""); private void GRIDLOG(string ulke, string url, string ip = "") { if (this.InvokeRequired) { // Pass the same function to BeginInvoke, // but the call would come on the correct // thread and InvokeRequired will be false. object[] myArray = new object[3]; myArray[0] = ulke; myArray[1] = url; myArray[2] = ip; this.BeginInvoke(new GRIDLOGDelegate(GRIDLOG), new object[] { myArray }); return; } //Yeni bir satir daha olustur string[] newRow = new string[] { ulke, url, ip }; dgLogGrid.Rows.Add(newRow); }

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  • localtime_r supposed to be thread safe, but causing errors in Valgrind DRD

    - by Nik
    I searched google as much as I could but I couldn't find any good answers to this. localtime_r is supposed to be a thread-safe function for getting the system time. However, when checking my application with Valgrind --tool=drd, it consistantly tells me that there is a data race condition on this function. Are the common search results lying to me, or am I just missing something? It doesn't seem efficient to surround each localtime_r call with a mutex, especially if it is supposed to by thread safe in the first place. here is how i'm using it: timeval handlerTime; gettimeofday(&handlerTime,NULL); tm handlerTm; localtime_r(&handlerTime.tv_sec,&handlerTm); Any ideas?

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  • Is this ruby code thread safe?

    - by Ben K.
    Is this code threadsafe? It seems like it should be, because @myvar will never be assigned from multiple threads (assuming block completes in < 1s). But do I need to be worried about a situation where the second block is trying to read @myvar as it's being written? require 'rubygems' require 'eventmachine' @myvar = Time.now.to_i EventMachine.run do EventMachine.add_periodic_timer(1) do EventMachine.defer do @myvar = Time.now.to_i # some calculation and reassign end end EventMachine.add_periodic_timer(0.5) do puts @myvar end end

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  • [WPF] The calling thread cannot access this object because a different thread owns it.

    - by zunyite
    Why I can't create CroppedBitmap in the following code ? I got an exception : The calling thread cannot access this object because a different thread owns it. public MainWindow() { InitializeComponent(); ThreadPool.QueueUserWorkItem((o) => { //load a large image file var bf = BitmapFrame.Create( new Uri("D:\\1172735642.jpg"), BitmapCreateOptions.DelayCreation | BitmapCreateOptions.IgnoreColorProfile, BitmapCacheOption.None); bf.Freeze(); Dispatcher.BeginInvoke( new Action(() => { CroppedBitmap cb = new CroppedBitmap(bf, new Int32Rect(1,1,5,5)); cb.Freeze(); //set Image's source to cb.... }), System.Windows.Threading.DispatcherPriority.ApplicationIdle); } ); }

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  • Java Thread - Synchronization issue

    - by Yatendra Goel
    From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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  • Python Threading, loading one thread after another

    - by Michael
    Hi, I'm working on a media player and am able to load in a single .wav and play it. As seen in the code below. foo = wx.FileDialog(self, message="Open a .wav file...", defaultDir=os.getcwd(), defaultFile="", style=wx.FD_MULTIPLE) foo.ShowModal() queue = foo.GetPaths() self.playing_thread = threading.Thread(target=self.playFile, args=(queue[0], 'msg')) self.playing_thread.start() But the problem is, when I try to make the above code into a loop for multiple .wav files. Such that while playing_thread.isActive == True, create and .start() the thread. Then if .isActive == False, pop queue[0] and load the next .wav file. Problem is, my UI will lock up and I'll have to terminate the program. Any ideas would be appreciated.

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  • ID generator with local static variable - thread-safe?

    - by Poseidon
    Will the following piece of code work as expected in a multi-threaded scenario? int getUniqueID() { static int ID=0; return ++ID; } It's not necessary that the IDs to be contiguous - even if it skips a value, it's fine. Can it be said that when this function returns, the value returned will be unique across all threads?

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  • OIM 11g : Multi-thread approach for writing custom scheduled job

    - by Saravanan V S
    In this post I have shared my experience of designing and developing an OIM schedule job that uses multi threaded approach for updating data in OIM using APIs.  I have used thread pool (in particular fixed thread pool) pattern in developing the OIM schedule job. The thread pooling pattern has noted advantages compared to thread per task approach. I have listed few of the advantage here ·         Threads are reused ·         Creation and tear-down cost of thread is reduced ·         Task execution latency is reduced ·         Improved performance ·         Controlled and efficient management of memory and resources used by threads More about java thread pool http://docs.oracle.com/javase/tutorial/essential/concurrency/pools.html The following diagram depicts the high-level architectural diagram of the schedule job that process input from a flat file to update OIM process form data using fixed thread pool approach    The custom scheduled job shared in this post is developed to meet following requirement 1)      Need to process a CSV extract that contains identity, account identifying key and list of data to be updated on an existing OIM resource account. 2)      CSV file can contain data for multiple resources configured in OIM 3)      List of attribute to update and mapping between CSV column to OIM fields may vary between resources The following are three Java class developed for this requirement (I have given only prototype of the code that explains how to use thread pools in schedule task) CustomScheduler.java - Implementation of TaskSupport class that reads and passes the parameters configured on the schedule job to Thread Executor class. package com.oracle.oim.scheduler; import java.util.HashMap; import com.oracle.oim.bo.MultiThreadDataRecon; import oracle.iam.scheduler.vo.TaskSupport; public class CustomScheduler extends TaskSupport {      public void execute(HashMap options) throws Exception {             /*  Read Schedule Job Parameters */             String param1 = (String) options.get(“Parameter1”);             .             int noOfThread = (int) options.get(“No of Threads”);             .             String paramn = (int) options.get(“ParamterN”); /* Provide all the required input configured on schedule job to Thread Pool Executor implementation class like 1) Name of the file, 2) Delimiter 3) Header Row Numer 4) Line Escape character 5) Config and resource map lookup 6) No the thread to create */ new MultiThreadDataRecon(all_required_parameters, noOfThreads).reconcile();       }       public HashMap getAttributes() { return null; }       public void setAttributes() {       } } MultiThreadDataRecon.java – Helper class that reads data from input file, initialize the thread executor and builds the task queue. package com.oracle.oim.bo; import <required file IO classes>; import  <required java.util classes>; import  <required OIM API classes>; import <csv reader api>; public class MultiThreadDataRecon {  private int noOfThreads;  private ExecutorService threadExecutor = null;  public MetaDataRecon(<required params>, int noOfThreads)  {       //Store parameters locally       .       .       this.noOfThread = noOfThread;  }        /**        *  Initialize         */  private void init() throws Exception {       try {             // Initialize CSV file reader API objects             // Initialize OIM API objects             /* Initialize Fixed Thread Pool Executor class if no of threads                 configured is more than 1 */             if (noOfThreads > 1) {                   threadExecutor = Executors.newFixedThreadPool(noOfThreads);             } else {                   threadExecutor = Executors.newSingleThreadExecutor();             }             /* Initialize TaskProcess clas s which will be executing task                 from the Queue */                TaskProcessor.initializeConfig(params);       } catch (***Exception e) {                   // TO DO       }  }       /**        *  Method to reconcile data from CSV to OIM        */ public void reconcile() throws Exception {        try {             init();             while(<csv file has line>){                   processRow(line);             }             /* Initiate thread shutdown */             threadExecutor.shutdown();             while (!threadExecutor.isTerminated()) {                 // Wait for all task to complete.             }            } catch (Exception e) {                   // TO DO            } finally {                   try {                         //Close all the file handles                   } catch (IOException e) {                         //TO DO                   }             }       }       /**        * Method to process         */       private void processRow(String row) {             // Create task processor instance with the row data              // Following code push the task to work queue and wait for next                available thread to execute             threadExecutor.execute(new TaskProcessor(rowData));       } } TaskProcessor.java – Implementation of “Runnable” interface that executes the required business logic to update data in OIM. package com.oracle.oim.bo; import <required APIs> class TaskProcessor implements Runnable {       //Initialize required member variables       /**        * Constructor        */       public TaskProcessor(<row data>) {             // Initialize and parse csv row       }       /*       *  Method to initialize required object for task execution       */       public static void initializeConfig(<params>) {             // Process param and initialize the required configs and object       }           /*        * (non-Javadoc)        *         * @see java.lang.Runnable#run()        */            public void run() {             if (<is csv data valid>){                   processData();             }       }  /**   * Process the the received CSV input   */  private void processData() {     try{       //Find the user in OIM using the identity matching key value from CSV       // Find the account to be update from user’s account based on account identifying key on CSV       // Update the account with data from CSV       }catch(***Exception e){           //TO DO       }   } }

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  • Google adwords API - credit card safety question

    - by user5650
    Google is asking me to fax credit card xerox in order to activate adwords API in MCC. 1) Are there alternatives to this - is there a 3rd party provider who will give me this service without me sending them the credit card info? 2) How secure is it to send my credit card fax via some online fax service? 3) Do you think they will reject the application if I hide my CVV number in the fax? Any other thoughts appreciated.

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  • Google adwords API - credit card safety question

    - by anon
    Hi, Google is asking me to fax credit card xerox in order to activate adwords API in MCC. This really sucks imo... they could have had prepaid option. In any case, my questions: 1) Are there alternatives to this - is there a 3rd party provider who will give me this service without me sending them the credit card info? 2) How secure is it to send my credit card fax via some online fax service? 3) Do you think they will reject the application if I hide my CVV number in the fax? Any other thoughts appreciated :) thanks

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  • 10 Facebook Safety Tips - How to Protect Yourself

    Whether you are new to Facebook or a long time user, you should be diligent in protecting yourself, your family, and your friends while using Facebook. Here are 10 tips to keep your Facebook experien... [Author: William Turley - Computers and Internet - March 25, 2010]

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  • Safety of purchasing country-specific domains from registrars?

    - by Marc Bollinger
    None of the previous questions tackle some of the one-off (or further) countries' registries, beyond .co.uk, .it, et al. or else I'd have found an answer myself. Is it safe to buy a domain from a foreign country TLD from a registrar? http://www.iana.org/domains/root/db/ I'm just looking for information for a vanity domain, so obviously I'm alright without an answer, but it's an unasked question (or at least, unanswered), and I'm not exactly in a hurry to give my credit card information over country lines, sight unseen.

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  • Safety of installing Ubuntu alongside Windows

    - by giowck
    Is it really safe to chose the "Install Ubuntu alongside Windows" option from the Ubuntu installation program? I never used that option, instead I used other tools such as partition magic or windows 7's disk tool to resize my partitions. Since I'm going to install Ubuntu across a lot windows (XP, Vista and 7) machines. It would not be nice to damage those Windows partitions. What is your experience? Can I use this feature without concerns?

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  • Guide To Be An Active Facebook Member With Safety

    These days many people from all over the world have a fun time by browsing online social networking websites like Facebook. The reason is that they are the superb means to be in contact with friends ... [Author: Susan Miller - Computers and Internet - May 17, 2010]

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  • Windows 7 Safety Tips

    The introduction of Microsoft's Windows 7 operating system meant many new features for its users in the way of both functionality and security. With Windows 8 on the horizon, Microsoft customers can expect even more improvements, including integrated security features to help provide a solid barrier against malware and other malicious creations that have made their way into the tech landscape. The Windows 8 release is still not here, however, so many running Windows 7 will have to wait for such enhancements. That is no excuse for security lapses though, as there are many steps you can take...

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  • Is a 1:* write:read thread system safe?

    - by Di-0xide
    Theoretically, thread-safe code should fix race conditions. Race conditions, as I understand it, occur because two threads attempt to write to the same location at the same time. However, what about a threading model in which a single thread is designed to write to a location, and several slave/worker threads simply read from the location? Assuming the value/timing at which they read the data isn't relevant/doesn't hinder the worker thread's outcome, wouldn't this be considered 'thread safe', or am I missing something in my logic?

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  • WebLogic stuck thread protection

    - by doublep
    By default WebLogic kills stuck threads after 15 min (600 s), this is controlled by StuckThreadMaxTime parameter. However, I cannot find more details on how exactly "stuckness" is defined. Specifically: What is the point at which 15 min countdown begins. Request processing start? Last wait()-like method? Something else? Does this apply only to request-processing threads or to all threads? I.e. can a request-processing thread "escape" this protection by spawning a worker thread for a long task? Especially, can it delegate response writing to such a worker without 15 min countdown? My usecase is download of huge files through a permission system. Since a user needs to be authenticated and have permissions to view a file, I cannot (or at least don't know how) leave this to a simple HTTP server, e.g. Apache. And because files can be huge, download could (at least in theory) take more than 15 minutes.

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  • while(1) block my recv thread

    - by zp26
    Hello. I have a problem with this code. As you can see a launch with an internal thread recv so that the program is blocked pending a given but will continue its execution, leaving the task to lock the thread. My program would continue to receive the recv data socket new_sd and so I entered an infinite loop (the commented code). The problem is that by entering the while (1) my program block before recv, but not inserting it correctly receives a string, but after that stop. Someone could help me make my recv always waiting for information? Thanks in advance for your help. -(IBAction)Chat{ [NSThread detachNewThreadSelector:@selector(riceviDatiServer) toTarget:self withObject:nil]; } -(void)riceviDatiServer{ NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init]; labelRicevuti.text = [[NSString alloc] initWithFormat:@"In attesa di ricevere i dati"]; char datiRicevuti[500]; int ricevuti; //while(1){ ricevuti = recv(new_sd, &datiRicevuti, 500, 0); labelRicevuti.text = [[NSString alloc] initWithFormat:@"%s", datiRicevuti]; //} [pool release]; }

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  • ASP.NET lock thread method

    - by Peter
    Hello, I'm developing an ASP.NET forms webapplication using C#. I have a method which creates a new Order for a customer. It looks similar to this; private string CreateOrder(string userName) { // Fetch current order Order order = FetchOrder(userName); if (order.OrderId == 0) { // Has no order yet, create a new one order.OrderNumber = Utility.GenerateOrderNumber(); order.Save(); } return order; } The problem here is, it is possible that 1 customer in two requests (threads) could cause this method to be called twice while another thread is also inside this method. This can cause two orders to be created. How can I properly lock this method, so it can only be executed by one thread at a time per customer? I tried; Mutex mutex = null; private string CreateOrder(string userName) { if (mutex == null) { mutex = new Mutex(true, userName); } mutex.WaitOne(); // Code from above mutex.ReleaseMutex(); mutex = null; return order; } This works, but on some occasions it hangs on WaitOne and I don't know why. Is there an error, or should I use another method to lock? Thanks

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