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  • Invoke does not exist in the current context?

    - by Pawan Kumar
    Invoke does not exist in the current context. The same method was not giving any error in Form.cs class but when I used in other class in same project it gives error. i am using threading on forms control. private void UpdateText(object fileName) { if (Textbox.InvokeRequired) { UpdateTextCallback back = new UpdateTextCallback(UpdateText); this.Invoke(back, new object[] { fileName }); } }

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  • What is the difference between Thread.Sleep(timeout) and ManualResetEvent.Wait(timeout)?

    - by Erik Forbes
    Both Thread.Sleep(timeout) and resetEvent.Wait(timeout) cause execution to pause for at least timeout milliseconds, so is there a difference between them? I know that Thread.Sleep causes the thread to give up the remainder of its time slice, thus possibly resulting in a sleep that lasts far longer than asked for. Does the Wait(timeout) method of a ManualResetEvent object have the same problem?

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  • Is it possible to store pointers in shared memory without using offsets?

    - by Joseph Garvin
    When using shared memory, each process may mmap the shared region into a different area of their address space. This means that when storing pointers within the shared region, you need to store them as offsets of the start of the shared region. Unfortunately, this complicates use of atomic instructions (e.g. if you're trying to write a lock free algorithm). For example, say you have a bunch of reference counted nodes in shared memory, created by a single writer. The writer periodically atomically updates a pointer 'p' to point to a valid node with positive reference count. Readers want to atomically write to 'p' because it points to the beginning of a node (a struct) whose first element is a reference count. Since p always points to a valid node, incrementing the ref count is safe, and makes it safe to dereference 'p' and access other members. However, this all only works when everything is in the same address space. If the nodes and the 'p' pointer are stored in shared memory, then clients suffer a race condition: x = read p y = x + offset Increment refcount at y During step 2, p may change and x may no longer point to a valid node. The only workaround I can think of is somehow forcing all processes to agree on where to map the shared memory, so that real pointers rather than offsets can be stored in the mmap'd region. Is there any way to do that? I see MAP_FIXED in the mmap documentation, but I don't know how I could pick an address that would be safe.

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  • Optimising speeds in HDF5 using Pytables

    - by Sree Aurovindh
    The problem is with respect to the writing speed of the computer (10 * 32 bit machine) and the postgresql query performance.I will explain the scenario in detail. I have data about 80 Gb (along with approprite database indexes in place). I am trying to read it from Postgresql database and writing it into HDF5 using Pytables.I have 1 table and 5 variable arrays in one hdf5 file.The implementation of Hdf5 is not multithreaded or enabled for symmetric multi processing.I have rented about 10 computers for a day and trying to write them inorder to speed up my data handling. As for as the postgresql table is concerned the overall record size is 140 million and I have 5 primary- foreign key referring tables.I am not using joins as it is not scalable So for a single lookup i do 6 lookup without joins and write them into hdf5 format. For each lookup i do 6 inserts into each of the table and its corresponding arrays. The queries are really simple select * from x.train where tr_id=1 (primary key & indexed) select q_t from x.qt where q_id=2 (non-primary key but indexed) (similarly five queries) Each computer writes two hdf5 files and hence the total count comes around 20 files. Some Calculations and statistics: Total number of records : 14,37,00,000 Total number of records per file : 143700000/20 =71,85,000 The total number of records in each file : 71,85,000 * 5 = 3,59,25,000 Current Postgresql database config : My current Machine : 8GB RAM with i7 2nd generation Processor. I made changes to the following to postgresql configuration file : shared_buffers : 2 GB effective_cache_size : 4 GB Note on current performance: I have run it for about ten hours and the performance is as follows: The total number of records written for each file is about 6,21,000 * 5 = 31,05,000 The bottle neck is that i can only rent it for 10 hours per day (overnight) and if it processes in this speed it will take about 11 days which is too high for my experiments. Please suggest me on how to improve. Questions: 1. Should i use Symmetric multi processing on those desktops(it has 2 cores with about 2 GB of RAM).In that case what is suggested or prefereable? 2. If i change my postgresql configuration file and increase the RAM will it enhance my process. 3. Should i use multi threading.. In that case any links or pointers would be of great help Thanks Sree aurovindh V

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  • Second Thread Holding Up Entire Program in C# Windows Form Application

    - by Brandon
    In my windows form application, I'm trying to test the user's ability to access a remote machine's shared folder. The way I'm doing this (and I'm sure that there are better ways...but I don't know of them) is to check for the existence of a specific directory on the remote machine (I'm doing this because of firewall/other security restrictions that I'm confronted with in my organization). If the user has rights to access the shared folder, then it returns in no time at all, but if they don't, it hangs forever. To solve this, I threw the check into another thread and wait only 1000 milliseconds before determining that the share can't be hit by the user. However, when I do this, it still hangs as if it was never run in the same thread. What is making it hang and how do I fix it? I would think that the fact that it is in a separate thread would allow me to just let the thread finish on it's own in the background. Here is my code: bool canHitInstallPath = false; Thread thread = new Thread(new ThreadStart(() => { canHitInstallPath = Directory.Exists(compInfo.InstallPath); })); thread.Start(); thread.Join(1000); if (canHitInstallPath == false) { throw new Exception("Cannot hit folder: " + compInfo.InstallPath); }

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  • How do I start up an NSRunLoop, and ensure that it has an NSAutoreleasePool that gets emptied?

    - by Nick Forge
    I have a "sync" task that relies on several "sub-tasks", which include asynchronous network operations, but which all require access to a single NSManagedObjectContext. Due to the threading requirements of NSManagedObjectContexts, I need every one of these sub-tasks to execute on the same thread. Due to the amount of processing being done in some of these tasks, I need them to be on a background thread. At the moment, I'm launching a new thread by doing this in my singleton SyncEngine object's -init method: [self performSelectorInBackground:@selector(initializeSyncThread) withObject:nil]; The -initializeSyncThread method looks like this: - (void)initializeSyncThread { self.syncThread = [NSThread currentThread]; self.managedObjectContext = [(MyAppDelegate *)[UIApplication sharedApplication].delegate createManagedObjectContext]; NSRunLoop *runLoop = [NSRunLoop currentRunLoop]; [runLoop run]; } Is this the correct way to start up the NSRunLoop for this thread? Is there a better way to do it? The run loop only needs to handle 'performSelector' sources, and it (and its thread) should be around for the lifetime of the process. When it comes to setting up an NSAutoreleasePool, should I do this by using Run Loop Observers to create the autorelease pool and drain it after every run-through?

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  • How to interrupt a thread performing a blocking socket connect?

    - by Jason R
    I have some code that spawns a pthread that attempts to maintain a socket connection to a remote host. If the connection is ever lost, it attempts to reconnect using a blocking connect() call on its socket. Since the code runs in a separate thread, I don't really care about the fact that it uses the synchronous socket API. That is, until it comes time for my application to exit. I would like to perform some semblance of an orderly shutdown, so I use thread synchronization primitives to wake up the thread and signal for it to exit, then perform a pthread_join() on the thread to wait for it to complete. This works great, unless the thread is in the middle of a connect() call when I command the shutdown. In that case, I have to wait for the connect to time out, which could be a long time. This makes the application appear to take a long time to shut down. What I would like to do is to interrupt the call to connect() in some way. After the call returns, the thread will notice my exit signal and shut down cleanly. Since connect() is a system call, I thought that I might be able to intentionally interrupt it using a signal (thus making the call return EINTR), but I'm not sure if this is a robust method in a POSIX threads environment. Does anyone have any recommendations on how to do this, either using signals or via some other method? As a note, the connect() call is down in some library code that I cannot modify, so changing to a non-blocking socket is not an option.

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  • Cocoa Touch - Display an Activity Indicator while loading a UITabBar View

    - by Aurum Aquila
    I have a UITabBar Application with two views that load large amounts of data from the web in their "viewWillAppear" methods. I want to show a progress bar or an activity indicator while this data is being retrieved, to make sure the user knows the app isn't frozen. I am aware that this has been asked before. I simply need some clarification on what seems to be a rather good solution. I have implimented the code in the example. The question's original asker later solved their problem, by putting the retrieval of data into another "thread". I understand the concept of threads, but I do not know how I would impliment this. With research, I have found that I need to move all of my heavy data retrieval into a background thread, as all of the UI updating occurs in the main thread. If one would be so kind as to provide an example for me, I would be very appreciative. I can provide parts of my existing code as necessary.

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  • Java socketserver: How to handle many incoming connections?

    - by SlappyTheFish
    I am writing a simple multithreaded socketserver and I am wondering how best to handle incoming connections: create a new thread for each new connection. The number of concurrent threads would be limited and waiting connections limited by specifying a backlog add all incoming connections into a queue and have a pool of worker threads that process the queue I am inclined to go for option 2 because I really don't want to refuse any connections, even under high loads, but I am wondering if there are any considerations I should be aware of with accepting effectively unlimited connections?

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  • Understanding Java Wait and Notify methods

    - by Maddy
    Hello all: I have a following program: import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class SimpleWaitNotify implements Runnable { final static Object obj = new Object(); static boolean value = true; public synchronized void flag() { System.out.println("Before Wait"); try { obj.wait(); } catch (InterruptedException e) { System.out.println("Thread interrupted"); } System.out.println("After Being Notified"); } public synchronized void unflag() { System.out.println("Before Notify All"); obj.notifyAll(); System.out.println("After Notify All Method Call"); } public void run() { if (value) { flag(); } else { unflag(); } } public static void main(String[] args) throws InterruptedException { ExecutorService pool = Executors.newFixedThreadPool(4); SimpleWaitNotify sWait = new SimpleWaitNotify(); pool.execute(sWait); SimpleWaitNotify.value = false; SimpleWaitNotify sNotify = new SimpleWaitNotify(); pool.execute(sNotify); pool.shutdown(); } } When I wait on obj, I get the following exception Exception in thread "pool-1-thread-1" java.lang.IllegalMonitorStateException: current thread not owner for each of the two threads. But if I use SimpleWaitNotify's monitor then the program execution is suspended. In other words, I think it suspends current execution thread and in turn the executor. Any help towards understanding what's going on would be duly appreciated. This is an area1 where the theory and javadoc seem straightforward, and since there aren't many examples, conceptually left a big gap in me.

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  • Does operator new allocate on THREAD heap?

    - by Jonas Byström
    My problem seems to be this: heap data allocated by one thread (that later dies) seems to die as well. As so: Thread X: starts Thread Y: starts Thread X: ptr = new some bytes Thread X: dies Thread Y: tries to use ptr - and crashes! So far, I've only seen this problem on Darwin (Mac OS 10.5 and 10.6), but haven't tried more other platforms than Windows and Linux (Ubuntu) where it works as expected. I've had this problem for some time, so any know-how or more information about this is highly appreciated!

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  • C# problem with two threads and hardware access

    - by mack369
    I'm creating an application which communicates with the device via FT2232H USB/RS232 converter. For communication I'm using FTD2XX_NET.dll library from FTDI website. I'm using two threads: first thread continuously reads data from the device the second thread is the main thread of the Windows Form Application I've got a problem when I'm trying to write any data to the device while the receiver's thread is running. The main thread simply hangs up on ftdiDevice.Write function. I tried to synchronize both threads so that only one thread can use Read/Write function at the same time, but it didn't help. Below code responsible for the communication. Note that following functions are methods of FtdiPort class. Receiver's thread private void receiverLoop() { if (this.DataReceivedHandler == null) { throw new BackendException("dataReceived delegate is not set"); } FTDI.FT_STATUS ftStatus = FTDI.FT_STATUS.FT_OK; byte[] readBytes = new byte[this.ReadBufferSize]; while (true) { lock (FtdiPort.threadLocker) { UInt32 numBytesRead = 0; ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead); if (ftStatus == FTDI.FT_STATUS.FT_OK) { this.DataReceivedHandler(readBytes, numBytesRead); } else { Trace.WriteLine(String.Format("Couldn't read data from ftdi: status {0}", ftStatus)); Thread.Sleep(10); } } Thread.Sleep(this.RXThreadDelay); } } Write function called from main thread public void Write(byte[] data, int length) { if (this.IsOpened) { uint i = 0; lock (FtdiPort.threadLocker) { this.ftdiDevice.Write(data, length, ref i); } Thread.Sleep(1); if (i != (int)length) { throw new BackendException("Couldnt send all data"); } } else { throw new BackendException("Port is closed"); } } Object used to synchronize two threads static Object threadLocker = new Object(); Method that starts the receiver's thread private void startReceiver() { if (this.DataReceivedHandler == null) { return; } if (this.IsOpened == false) { throw new BackendException("Trying to start listening for raw data while disconnected"); } this.receiverThread = new Thread(this.receiverLoop); //this.receiverThread.Name = "protocolListener"; this.receiverThread.IsBackground = true; this.receiverThread.Start(); } The ftdiDevice.Write function doesn't hang up if I comment following line: ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead);

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  • Why use SyncLocks in .NET for simple operations when Interlocked class is available?

    - by rwmnau
    I've been doing simple multi-threading in VB.NET for a while, and have just gotten into my first large multi-threaded project. I've always done everything using the Synclock statement because I didn't think there was a better way. I just learned about the Interlocked Class - it makes it look as though all this: Private SomeInt as Integer Private SomeInt_LockObject as New Object Public Sub IntrementSomeInt Synclock SomeInt_LockObject SomeInt += 1 End Synclock End Sub Can be replaced with a single statement: Interlocked.Increment(SomeInt) This handles all the locking internally and modifies the number. This would be much simpler than writing my own locks for simple operations (longer-running or more complicated operations obviously still need their own locking). Is there a reason why I'd rolling my own locking, using dedicated locking objects, when I can accomplish the same thing using the Interlocked methods?

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  • Java semaphore to syncronize printing to screen

    - by Travis Griswald
    I'm currently stuck on a bit of homework and was wondering if anyone could help - I have to use semaphores in java to syncronize printing letters from 2 threads - one printing "A" and one printing "B". I cannot print out more than 2 of the same character in a row, so output should look like AABABABABABBABABABABAABBAABBABABA At the moment I have 3 semaphores, a binary mutex set to 1, and a counting semaphore, and my thread classes look something like this - public void run() { while (true) { Time.delay(RandomGenerator.integer(0,20)); Semaphores.mutex.down (); System.out.println (produce()); if (printCount > 1) { printCount = 0; Semaphores.mutex.up (); Semaphores.printB.up(); } } } public String produce() { printCount++; return "A"; } public void run() { while (true) { Time.delay(RandomGenerator.integer(0,20)); Semaphores.mutex.down (); System.out.println (produce()); if (printCount > 1) { printCount = 0; Semaphores.mutex.up (); Semaphores.printA.up(); } } } public String produce() { printCount++; return "B"; } Yet whatever I try it either deadlocks, or it seems to be working only printing 2 in a row at most, but always seems to print 3 in a row every now and again! Any help is much appreciated, not looking code or anything just a few pointers if possible :)

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  • Error in writting a class.

    - by Richard
    I am running through a tutorial online at http://www.sthurlow.com/python/lesson08/ and I believe I understand how classes work in python, at least to some degree but when I run this code: class Shape: def init(self,x,y): self.x = x self.y = y description = "This shape has not been described yet" author = "Nobody has claimed to make this shape yet" def area(self): return self.x * self.y def perimeter(self): return 2 * self.x + 2 * self.y def describe(self,text): self.description = text def authorName(self,text): self.author = text def scaleSize(self,scale): self.x = self.x * scale self.y = self.y * scale I get this error: Traceback (most recent call last): File "Y:/python/Shape.py", line 1, in -toplevel- class Shape: File "Y:/python/Shape.py", line 17, in Shape self.y = self.y * scale NameError: name 'self' is not defined Any Help would be great Thanks Richard

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  • Update C# Chart using BackgroundWorker

    - by Mark
    I am currently trying to update a chart which is on my form to the background worker using: bwCharter.RunWorkerAsync(chart1); Which runs: private void bcCharter_DoWork(object sender, DoWorkEventArgs e) { System.Windows.Forms.DataVisualization.Charting.Chart chart = null; // Convert e.Argument to chart //.. // Converted.. chart.Series.Clear(); e.Result=chart; setChart(c.chart); } private void setChart(System.Windows.Forms.DataVisualization.Charting.Chart arg) { if (chart1.InvokeRequired) { chart1.Invoke(new MethodInvoker(delegate { setChart(arg); })); return; } chart1 = arg; } However, at the point of clearing the series, an exception is thrown. Basically, I want to do a whole lot more processing after clearing the series, which slows the GUI down completely - so wanted this in another thread. I thought that by passing it as an argument, I should be safe, but apparently not! Interestingly, the chart is on a tab page. I can run this over and over if the tabpage is in the background, but if I run this, look at the chart, hide it again, and re-run, it throws the exception. Obviously, it throws if the chart is in the foreground as well. Can anyone suggest what I can do differently? Thanks!

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  • How to re-use a thread in Java ?

    - by David
    I am a building a console Sudoku Solver where the main objective is raw speed. I now have a ManagerThread that starts WorkerThreads to compute the neibhbors of each cell. So one WorkerThread is started for each cell right now. How can I re-use an existing thread that has completed its work? The Thread Pool Pattern seems to be the solution, but I don't understand what to do to prevent the thread from dying once its job has been completed. ps : I do not expect to gain much performance for this particular task, just want to experiment how multi-threading works before applying it to the more complex parts of the code. Thanks

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  • SwingWorker in Java (beginner question)

    - by Malachi
    I am relatively new to multi-threading and want to execute a background task using a Swingworker thread - the method that is called does not actually return anything but I would like to be notified when it has completed. The code I have so far doesn't appear to be working: private void crawl(ActionEvent evt) { try { SwingWorker<Void, Void> crawler = new SwingWorker<Void, Void>() { @Override protected Void doInBackground() throws Exception { Discoverer discover = new Discoverer(); discover.crawl(); return null; } @Override protected void done() { JOptionPane.showMessageDialog(jfThis, "Finished Crawling", "Success", JOptionPane.INFORMATION_MESSAGE); } }; crawler.execute(); } catch (Exception ex) { JOptionPane.showMessageDialog(this, ex.getMessage(), "Exception", JOptionPane.ERROR_MESSAGE); } } Any feedback/advice would be greatly appreciated as multi-threading is a big area of programming that I am weak in.

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  • can i know the Thread runnable class attributes in java?

    - by dori naji
    probability this question have been asked before but i cant find anything in my searching mechanism. I am trying to create a multiple threads, in an array list but i want to retrieve them from an arraylist and filter them by the attribute of w1 i used in my code. any ideas ? w1 = new FirstWorker(ProductsList, OrdersList, s); FirstWorkerThread = new Thread(w1); ThreadArrayList.add(FirstWorkerThread); //I know i cant do the code below but i want to do that how ? for(Thread x : ThreadArrayList){ x.ProductsList } this is FirstWorker class import java.lang.String; import java.util.HashMap; /* * To change this template, choose Tools | Templates and open the template in * the editor. */ /** * * @author Dimitris */ public class FirstWorker extends Thread implements Runnable { private OrderList orderlist; private ProductList productlist; private String Worker; boolean Stop; private int speed = 1000; public FirstWorker(ProductList productlist, OrderList orderlist, String Worker) { this.productlist = productlist; this.orderlist = orderlist; this.Worker = Worker; this.Stop = true; } public void run() { if (Stop == true) { try { Thread.sleep(100); } catch (InterruptedException e) { } while (orderlist.returnLengthofOrder() != 0) { if (Thread.interrupted()) { System.out.println("I am in the thread inturrupt"); // We've been interrupted: no more crunching. return; } if (orderlist.getDone() == true) { } else if (orderlist.getDone() == false) { orderlist.setDoneTrue(); orderlist.Purchased(Worker); orderlist.setDoneFalse(); try { Thread.sleep(this.speed); } catch (InterruptedException e) { return; } } } } } public void setWork() { Stop = false; } public void setSpeed(int speed) { this.speed = speed; } }

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  • Thread Proc for an instancable class?

    - by user146780
    Basically I have a class and it is instincable (not static). Basically I want the class to be able to generate its own threads and manage its own stuff. I don't want to make a global callback for each instance I make, this doesnt seem clean and proper to me. What is the proper way of doing what I want. If I try to pass the threadproc to CreateThread and it is the proc from a class instance the compiler says I cannot do this. What is the best way of achieving what I want? Thanks

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  • Async Socket Listener on separate thread - VB.net

    - by TheHockeyGeek
    I am trying to use the code from Microsoft for an Async Socket connection. It appears the listener runs in the main thread locking the GUI. I am new at both socket connections and multi-threading all at the same time. Having a hard time getting my mind wrapped around this all at once. The code used is at http://msdn.microsoft.com/en-us/library/fx6588te.aspx Using this example, how can I move the listener to its own thread? Public Shared Sub Main() ' Data buffer for incoming data. Dim bytes() As Byte = New [Byte](1023) {} ' Establish the local endpoint for the socket. Dim ipHostInfo As IPHostEntry = Dns.GetHostEntry(Dns.GetHostName()) Dim ipAddress As IPAddress = ipHostInfo.AddressList(1) Dim localEndPoint As New IPEndPoint(ipAddress, 11000) ' Create a TCP/IP socket. Dim listener As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) ' Bind the socket to the local endpoint and listen for incoming connections. listener.Bind(localEndPoint) listener.Listen(100)

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  • Kill a Perl system call after a timeout

    - by Fergal
    I've got a Perl script I'm using for running a file processing tool which is started using backticks. The problem is that occasionally the tool hangs and It needs to be killed in order for the rest of the files to be processed. Whats the best way best way to apply a timeout after which the parent script will kill the hung process? At the moment I'm using: foreach $file (@FILES) { $runResult = `mytool $file >> $file.log`; } But when mytool hangs after n seconds I'd like to be able to kill it and continue to the next file.

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  • {DCC Warning} W1036 Variable '$frame' might not have been initialized?

    - by Gad D Lord
    Any ideas why I get this warning in Delphi XE: [DCC Warning] Form1.pas(250): W1036 Variable '$frame' might not have been initialized procedure TForm1.Action1Execute(Sender: TObject); var Thread: TThread; begin ... Thread := TThread.CreateAnonymousThread( procedure{Anonymos}() procedure ShowLoading(const Show: Boolean); begin /// <------------- WARNING IS GIVEN FOR THIS LINE (line number 250) Thread.Synchronize(Thread, procedure{Anonymous}() begin ... Button1.Enabled := not Show; ... end ); end; var i: Integer; begin ShowLoading(true); try Thread.Synchronize(Thread, procedure{Anonymous}() begin ... // some UI updates end Thread.Synchronize(Thread, procedure{Anonymous}() begin ... // some UI updates end ); finally ShowLoading(false); end; end ).NameThread('Some Thread Name'); Thread.Start; end; I do not have anywhere in my code a variable names frame nor $frame. I am even not sure how $frame with $ sign can be a valid identifier. Smells like compiler magic to me. PS: Of course the real life xosw is having other than Form1, Button1, Action1 names.

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  • Thread pool in scala

    - by ghedas
    I have a project that is actor-based and for one part of it I must use some actors that receive message after that one actor assigns to each request separately and each actor is responsible for doing its message request, so I need something like a thread pool for actors of my project, are there any features in Scala that is useful for my necessity? how can I achieve this goal? tanks a lot for your attention!

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