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• How difficult is Haskell multi-threading?

  - by mvid

  I have heard that in Haskell, creating a multi-threaded application is as easy as taking a standard Haskell application and compiling it with the -threaded flag. Other cases, however, have described the use of a par command within the actual source code. What is the state of Haskell multi-threading? How easy is it to introduce into programs? Is there a good multi-threading tutorial that goes over these different commands and their uses?

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• synchronized block vs synchronized method?

  - by Warrior

  Can any one tell me the advantage of synchronized method over synchronized block with an example?Thanks.

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• non blocking client server chat application in java using nio

  - by Amith

  I built a simple chat application using nio channels. I am very much new to networking as well as threads. This application is for communicating with server (Server / Client chat application). My problem is that multiple clients are not supported by the server. How do I solve this problem? What's the bug in my code? public class Clientcore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void coreClient() { System.out.println("please enter the text"); BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in)); SocketChannel sc = null; try { sc = SocketChannel.open(); sc.configureBlocking(false); sc.connect(new InetSocketAddress(8888)); int i=0; while (!sc.finishConnect()) { } for(int ii=0;ii>-22;ii++) { System.out.println("Enter the text"); String HELLO_REQUEST =stdin.readLine().toString(); if(HELLO_REQUEST.equalsIgnoreCase("end")) { break; } System.out.println("Sending a request to HelloServer"); ByteBuffer buffer = ByteBuffer.wrap(HELLO_REQUEST.getBytes()); sc.write(buffer); } } catch (IOException e) { e.printStackTrace(); } finally { if (sc != null) { try { sc.close(); } catch (Exception e) { e.printStackTrace(); } } } } public void run() { try { coreClient(); } catch(Exception ej) { ej.printStackTrace(); }}} public class ServerCore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void run() { try { coreServer(); } catch(Exception ej) { ej.printStackTrace(); } } private void coreServer() { try { ServerSocketChannel ssc = ServerSocketChannel.open(); try { ssc.socket().bind(new InetSocketAddress(8888)); while (true) { sckt_manager=SelectorProvider.provider().openSelector(); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); register_server(ssc,SelectionKey.OP_ACCEPT); if (sc == null) { } else { System.out.println("Received an incoming connection from " + sc.socket().getRemoteSocketAddress()); printRequest(sc); System.err.println("testing 1"); String HELLO_REPLY = "Sample Display"; ByteBuffer buffer = ByteBuffer.wrap(HELLO_REPLY.getBytes()); System.err.println("testing 2"); sc.write(buffer); System.err.println("testing 3"); sc.close(); }}} catch (IOException e) { e.printStackTrace(); } finally { if (ssc != null) { try { ssc.close(); } catch (IOException e) { e.printStackTrace(); } } } } catch(Exception E) { System.out.println("Ex in servCORE "+E); } } private static void printRequest(SocketChannel sc) throws IOException { ReadableByteChannel rbc = Channels.newChannel(sc.socket().getInputStream()); WritableByteChannel wbc = Channels.newChannel(System.out); ByteBuffer b = ByteBuffer.allocate(1024); // read 1024 bytes while (rbc.read(b) != -1) { b.flip(); while (b.hasRemaining()) { wbc.write(b); System.out.println(); } b.clear(); } } public void register_server(ServerSocketChannel ssc,int selectionkey_ops)throws Exception { ssc.register(sckt_manager,selectionkey_ops); }} public class HelloClient { public void coreClientChat() { Clientcore t=new Clientcore(); new Thread(t).start(); } public static void main(String[] args)throws Exception { HelloClient cl= new HelloClient(); cl.coreClientChat(); }} public class HelloServer { public void coreServerChat() { ServerCore t=new ServerCore(); new Thread(t).start(); } public static void main(String[] args) { HelloServer st= new HelloServer(); st.coreServerChat(); }}

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• What threading analysis tools do you recommend?

  - by glutz78

  My primary IDE is Visual Studio 2005 and I have a large C/C++ project. I'm interested in what thread analysis tools are recommended. By that I mean, I want a tool, static or dynamic, to help find race conditions, deadlocks, and the like. So far I've casually researched the following: 1. Intel Thread Checker: I don't believe that it ties into VS 2005? 2. Valgrind/Helgrind: free. 3. Coverity: this is a costly tool if i understand correctly. Anyone have experience with any of these or other? I'd much appreciate any advice. Thank you.

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• Windows 7 - pydoc from cmd

  - by Random_Person

  Okay, I'm having one of those moments that makes me question my ability to use a computer. This is not the sort of question I imagined asking as my first SO post, but here goes. Started on Zed's new "Learn Python the Hard Way" since I've been looking to get back into programming after a 10 year hiatus and python was always what I wanted. This book has really spoken to me. That being said, I'm having a serious issue with pydoc from the command. I've got all the directories in c:/python26 in my system path and I can execute pydoc from the command line just fine regardless of pwd - but it accepts no arguments. Doesn't matter what I type, I just get the standard pydoc output telling me the acceptable arguments. Any ideas? For what it's worth, I installed ActivePython as per Zed's suggestion. C:\Users\Chevee>pydoc file pydoc - the Python documentation tool pydoc.py <name> ... Show text documentation on something. <name> may be the name of a Python keyword, topic, function, module, or package, or a dotted reference to a class or function within a module or module in a package. If <name> contains a '\', it is used as the path to a Python source file to document. If name is 'keywords', 'topics', or 'modules', a listing of these things is displayed. pydoc.py -k <keyword> Search for a keyword in the synopsis lines of all available modules. pydoc.py -p <port> Start an HTTP server on the given port on the local machine. pydoc.py -g Pop up a graphical interface for finding and serving documentation. pydoc.py -w <name> ... Write out the HTML documentation for a module to a file in the current directory. If <name> contains a '\', it is treated as a filename; if it names a directory, documentation is written for all the contents. C:\Users\Chevee> EDIT: New information, pydoc works just fine in PowerShell. As a linux user, I have no idea why I'm trying to use cmd anyways--but I'd still love to figure out what's up with pydoc and cmd. EDIT 2: More new information. In cmd... c:\>python c:/python26/lib/pydoc.py file ...works just fine. Everything works just fine with just pydoc in PowerShell without me worrying about pwd, or extensions or paths.

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• How to estimate the thread context switching overhead?

  - by Ignas Limanauskas

  I am trying to improve the performance of the threaded application with real-time deadlines. It is running on Windows Mobile and written in C / C++. I have a suspicion that high frequency of thread switching might be causing tangible overhead, but can neither prove it or disprove it. As everybody knows, lack of proof is not a proof of opposite :). Thus my question is twofold: If exists at all, where can I find any actual measurements of the cost of switching thread context? Without spending time writing a test application, what are the ways to estimate the thread switching overhead in the existing application? Does anyone know a way to find out the number of context switches (on / off) for a given thread?

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• Is there a limit on the number of mutex objects that can be created in a Windows process?

  - by young-phillip

  I'm writing a c# application that can create a series of request messages. Each message could have a response, that needs to be waited on by a consumer. Where the number of outstanding request messages is constrained, I have used the windows EVENT to solve this problem. However, I know there is a limit on how many EVENT objects can be created in a single process, and in this instance, its possible I might exceed that limit. Does anyone know if there is a similar limit on creation of mutex objects or semaphores? I know this can be solved by some sort of pool of shared resources, that are grabbed by consumers when they need to wait, but it would be more convenient if each request message could have its own sync object.

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• How to check how many threads are waiting for a synchronized method to become unlocked

  - by MontyBongo

  Is there any way to check how many threads are waiting for a synchronized method to become unlocked? I would like to know when the thread calls a synchronized method: 1) How many threads are already waiting to call the method? 2) Once the method is called how long it needed to wait for the method to become unlocked?

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• Issue with maxWorkerThreads and thread count

  - by Kartik M

  I have created an ASP.NET application which creates threads in an infinite loop. I set maxWorkerThreads to 20 in processModel in machine.config. When I checked the Thread count in perfmon there was around 7000 threads created in worker process. In PageLoad() I have: using System.Threading; ... int count = 0; var threadList = new System.Collections.Generic.List<System.Threading.Thread>(); try { while (true) { Thread newThread = new Thread(ThreadStart(DummyCall), 1024); newThread.Start(); threadList.Add(newThread); count++; } } catch (Exception ex) { Response.Write(count + " : " + ex.ToString()); } Function: void DummyCall() { System.Threading.Thread.Sleep(1000000000); } How do I restrict thread creation in ASP.NET with IIS6/7?

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• How can I make these images download on a separate thread?

  - by Andy Barlow

  I have the following code running on my Android device. It works great and displays my list items wonderfully. It's also clever in the fact it only downloads the data when it's needed by the ArrayAdapter. However, whilst the download of the thumbnail is occurring, the entire list stalls and you cannot scroll until it's finished downloading. Is there any way of threading this so it'll still scroll happily, maybe show a place holder for the downloading image, finish the download, and then show? Any help with this would be really appreciated. private class CatalogAdapter extends ArrayAdapter<SingleQueueResult> { private ArrayList<SingleQueueResult> items; //Must research what this actually does! public CatalogAdapter(Context context, int textViewResourceId, ArrayList<SingleQueueResult> items) { super(context, textViewResourceId, items); this.items = items; } /** This overrides the getview of the ArrayAdapter. It should send back our new custom rows for the list */ @Override public View getView(int position, View convertView, ViewGroup parent) { View v = convertView; if (v == null) { LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE); v = vi.inflate(R.layout.mylists_rows, null); } final SingleQueueResult result = items.get(position); // Sets the text inside the rows as they are scrolled by! if (result != null) { TextView title = (TextView)v.findViewById(R.id.mylist_title); TextView format = (TextView)v.findViewById(R.id.mylist_format); title.setText(result.getTitle()); format.setText(result.getThumbnail()); // Download Images ImageView myImageView = (ImageView)v.findViewById(R.id.mylist_thumbnail); downloadImage(result.getThumbnail(), myImageView); } return v; } } // This should run in a seperate thread public void downloadImage(String imageUrl, ImageView myImageView) { try { url = new URL(imageUrl); URLConnection conn = url.openConnection(); conn.connect(); InputStream is = conn.getInputStream(); BufferedInputStream bis = new BufferedInputStream(is); Bitmap bm = BitmapFactory.decodeStream(bis); bis.close(); is.close(); myImageView.setImageBitmap(bm); } catch (IOException e) { /* Reset to Default image on any error. */ //this.myImageView.setImageDrawable(getResources().getDrawable(R.drawable.default)); } }

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• How to catch exception in the main thread if the exception occurs in the secondary thread?

  - by Ashish Ashu

  How to catch exception in the main thread if the exception occurs in the secondary thread? The code snippet for the scenario is given below: private void button1_Click(object sender, EventArgs e) { try { Thread th1 = new Thread(new ThreadStart(Test)); th1.Start(); } catch (Exception) { } } void Test() { for (int i = 0; i < 100; i++) { Thread.Sleep(100); if (i == 2) throw new MyException(); } } }

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• Cross-thread operation not valid: Control accessed from a thread other than the thread it was create

  - by SilverHorse

  I have a scenario. (Windows Forms, C#, .NET) There is a main form which hosts some user control. The user control does some heavy data operation, such that if I directly call the Usercontrol_Load method the UI become nonresponsive for the duration for load method execution. To overcome this I load data on different thread (trying to change existing code as little as I can) I used a background worker thread which will be loading the data and when done will notify the application that it has done its work. Now came a real problem. All the UI (main form and its child usercontrols) was created on the primary main thread. In the LOAD method of the usercontrol I'm fetching data based on the values of some control (like textbox) on userControl. The pseudocode would look like this: //CODE 1 UserContrl1_LOadDataMethod() { if(textbox1.text=="MyName") <<======this gives exception { //Load data corresponding to "MyName". //Populate a globale variable List<string> which will be binded to grid at some later stage. } } The Exception it gave was Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on. To know more about this I did some googling and a suggestion came up like using the following code //CODE 2 UserContrl1_LOadDataMethod() { if(InvokeRequired) // Line #1 { this.Invoke(new MethodInvoker(UserContrl1_LOadDataMethod)); return; } if(textbox1.text=="MyName") //<<======Now it wont give exception** { //Load data correspondin to "MyName" //Populate a globale variable List<string> which will be binded to grid at some later stage } } BUT BUT BUT... it seems I'm back to square one. The Application again become nonresponsive. It seems to be due to the execution of line #1 if condition. The loading task is again done by the parent thread and not the third that I spawned. I don't know whether I perceived this right or wrong. I'm new to threading. How do I resolve this and also what is the effect of execution of Line#1 if block? The situation is this: I want to load data into a global variable based on the value of a control. I don't want to change the value of a control from the child thread. I'm not going to do it ever from a child thread. So only accessing the value so that the corresponding data can be fetched from the database.

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• Closing a hook that captures global input events

  - by Margus

  Intro Here is an example to illustrate the problem. Consider I am tracking and displaying mouse global current position and last click button and position to the user. Here is an image: To archive capturing click events on windows box, that would and will be sent to the other programs event messaging queue, I create a hook using winapi namely user32.dll library. This is outside JDK sandbox, so I use JNA to call the native library. This all works perfectly, but it does not close as I expect it to. My question is - How do I properly close following example program? Example source Code below is not fully written by Me, but taken from this question in Oracle forum and partly fixed. import java.awt.AWTException; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.GridLayout; import java.awt.MouseInfo; import java.awt.Point; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JFrame; import javax.swing.JLabel; import com.sun.jna.Native; import com.sun.jna.NativeLong; import com.sun.jna.Platform; import com.sun.jna.Structure; import com.sun.jna.platform.win32.BaseTSD.ULONG_PTR; import com.sun.jna.platform.win32.Kernel32; import com.sun.jna.platform.win32.User32; import com.sun.jna.platform.win32.WinDef.HWND; import com.sun.jna.platform.win32.WinDef.LRESULT; import com.sun.jna.platform.win32.WinDef.WPARAM; import com.sun.jna.platform.win32.WinUser.HHOOK; import com.sun.jna.platform.win32.WinUser.HOOKPROC; import com.sun.jna.platform.win32.WinUser.MSG; import com.sun.jna.platform.win32.WinUser.POINT; public class MouseExample { final JFrame jf; final JLabel jl1, jl2; final CWMouseHook mh; final Ticker jt; public class Ticker extends Thread { public boolean update = true; public void done() { update = false; } public void run() { try { Point p, l = MouseInfo.getPointerInfo().getLocation(); int i = 0; while (update == true) { try { p = MouseInfo.getPointerInfo().getLocation(); if (!p.equals(l)) { l = p; jl1.setText(new GlobalMouseClick(p.x, p.y) .toString()); } Thread.sleep(35); } catch (InterruptedException e) { e.printStackTrace(); return; } } } catch (Exception e) { update = false; } } } public MouseExample() throws AWTException, UnsupportedOperationException { this.jl1 = new JLabel("{}"); this.jl2 = new JLabel("{}"); this.jf = new JFrame(); this.jt = new Ticker(); this.jt.start(); this.mh = new CWMouseHook() { @Override public void globalClickEvent(GlobalMouseClick m) { jl2.setText(m.toString()); } }; mh.setMouseHook(); jf.setLayout(new GridLayout(2, 2)); jf.add(new JLabel("Position")); jf.add(jl1); jf.add(new JLabel("Last click")); jf.add(jl2); jf.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent we) { mh.dispose(); jt.done(); jf.dispose(); } }); jf.setLocation(new Point(0, 0)); jf.setPreferredSize(new Dimension(200, 90)); jf.pack(); jf.setVisible(true); } public static class GlobalMouseClick { private char c; private int x, y; public GlobalMouseClick(char c, int x, int y) { super(); this.c = c; this.x = x; this.y = y; } public GlobalMouseClick(int x, int y) { super(); this.x = x; this.y = y; } public char getC() { return c; } public void setC(char c) { this.c = c; } public int getX() { return x; } public void setX(int x) { this.x = x; } public int getY() { return y; } public void setY(int y) { this.y = y; } @Override public String toString() { return (c != 0 ? c : "") + " [" + x + "," + y + "]"; } } public static class CWMouseHook { public User32 USER32INST; public CWMouseHook() throws UnsupportedOperationException { if (!Platform.isWindows()) { throw new UnsupportedOperationException( "Not supported on this platform."); } USER32INST = User32.INSTANCE; mouseHook = hookTheMouse(); Native.setProtected(true); } private static LowLevelMouseProc mouseHook; private HHOOK hhk; private boolean isHooked = false; public static final int WM_LBUTTONDOWN = 513; public static final int WM_LBUTTONUP = 514; public static final int WM_RBUTTONDOWN = 516; public static final int WM_RBUTTONUP = 517; public static final int WM_MBUTTONDOWN = 519; public static final int WM_MBUTTONUP = 520; public void dispose() { unsetMouseHook(); mousehook_thread = null; mouseHook = null; hhk = null; USER32INST = null; } public void unsetMouseHook() { isHooked = false; USER32INST.UnhookWindowsHookEx(hhk); System.out.println("Mouse hook is unset."); } public boolean isIsHooked() { return isHooked; } public void globalClickEvent(GlobalMouseClick m) { System.out.println(m); } private Thread mousehook_thread; public void setMouseHook() { mousehook_thread = new Thread(new Runnable() { @Override public void run() { try { if (!isHooked) { hhk = USER32INST.SetWindowsHookEx(14, mouseHook, Kernel32.INSTANCE.GetModuleHandle(null), 0); isHooked = true; System.out .println("Mouse hook is set. Click anywhere."); // message dispatch loop (message pump) MSG msg = new MSG(); while ((USER32INST.GetMessage(msg, null, 0, 0)) != 0) { USER32INST.TranslateMessage(msg); USER32INST.DispatchMessage(msg); if (!isHooked) break; } } else System.out .println("The Hook is already installed."); } catch (Exception e) { System.err.println("Caught exception in MouseHook!"); } } }); mousehook_thread.start(); } private interface LowLevelMouseProc extends HOOKPROC { LRESULT callback(int nCode, WPARAM wParam, MOUSEHOOKSTRUCT lParam); } private LowLevelMouseProc hookTheMouse() { return new LowLevelMouseProc() { @Override public LRESULT callback(int nCode, WPARAM wParam, MOUSEHOOKSTRUCT info) { if (nCode >= 0) { switch (wParam.intValue()) { case CWMouseHook.WM_LBUTTONDOWN: globalClickEvent(new GlobalMouseClick('L', info.pt.x, info.pt.y)); break; case CWMouseHook.WM_RBUTTONDOWN: globalClickEvent(new GlobalMouseClick('R', info.pt.x, info.pt.y)); break; case CWMouseHook.WM_MBUTTONDOWN: globalClickEvent(new GlobalMouseClick('M', info.pt.x, info.pt.y)); break; default: break; } } return USER32INST.CallNextHookEx(hhk, nCode, wParam, info.getPointer()); } }; } public class Point extends Structure { public class ByReference extends Point implements Structure.ByReference { }; public NativeLong x; public NativeLong y; } public static class MOUSEHOOKSTRUCT extends Structure { public static class ByReference extends MOUSEHOOKSTRUCT implements Structure.ByReference { }; public POINT pt; public HWND hwnd; public int wHitTestCode; public ULONG_PTR dwExtraInfo; } } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { new MouseExample(); } catch (AWTException e) { e.printStackTrace(); } } }); } }

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• ASP.NET Exception Handling in background threads

  - by Xodarap

  When I do ThreadPool.QueueUserWorkItem, I don't want unhandled exceptions to kill my entire process. So I do something like: ThreadPool.QueueUserWorkItem(delegate() { try { FunctionIActuallyWantToCall(); } catch { HandleException(); } }); Is this the recommended pattern? It seems like there should be a simpler way to do this. It's in an asp.net-mvc app, if that's relevant.

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• Sending multiple requests simultaneously to the Server using Selenium with Java

  - by gagneet

  I wish to send multiple requests to the server, simultaneously. The problem statement will be: Read a text file containing multiple URL’s. Open each URL in the web browser. Collect the Cookie information for each call, and store it to a file. Send another call: http://myserver.com:1111/cookie?out=text Store the output (body text) of this file to a separate file for each call made in 4 Open the next URL in the text file given in 1 and repeat steps 1-6. The above is to be run with multi-threading, so that I can send around 5-10 URL requests simultaneously. I have implemented something in Selenium using Java, but have not been able to do the multi-threading approach. Code is given below: package com.cookie.selenium; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import com.thoughtworks.selenium.*; public class ReadURL extends SeleneseTestCase { public void setUp() throws Exception { setUp("http://www.myserver.com/", "*chrome"); } public static void main(String args[]) { Selenium selenium = new DefaultSelenium("localhost", 4444, "*chrome", "http://myserver"); selenium.start(); selenium.setTimeout("30000000"); try { BufferedReader inputfile = new BufferedReader(new FileReader("C:\\url.txt")); BufferedReader cookietextfile = new BufferedReader(new FileReader("C:\\text.txt")); BufferedWriter cookiefile = new BufferedWriter(new FileWriter("C:\\cookie.txt")); BufferedWriter outputfile = null; String str; String cookiestr = "http://myserver.com:1111/cookie?out=text"; String filename = null; int i = 0; while ((str = inputfile.readLine()) != null) { selenium.createCookie("T=222redHyt345&f=5&r=fg&t=100",""); selenium.open( str ); selenium.waitForPageToLoad("120000"); String urlcookie = selenium.getCookie(); System.out.println( "URL :" + str ); System.out.println( "Cookie :" + urlcookie ); cookiefile.write( urlcookie ); cookiefile.newLine(); selenium.open( cookiestr ); selenium.waitForPageToLoad("120000"); String bodytext = selenium.getBodyText(); System.out.println("Body Text :" + bodytext); filename = "C:\\cookies\\" + i + ".txt"; outputfile = new BufferedWriter(new FileWriter( filename )); outputfile.write( bodytext ); outputfile.newLine(); i++; } inputfile.close(); outputfile.close(); cookiefile.close(); selenium.stop(); } catch (IOException e) { } } } What basically I am trying to do here is, open the first set of URL from a text file (which has list given of all the URL's i wish to open). Then when I capture the cookie information from here and store it, I open another window to output all the cookie information for that server to my browser window. This works fine when I do outside of Selenium code, but when I do it within the above code, it opens a "Save As..." popup and my tests stop. :-( I wish to save the contents of that second call to a new file, but have not been able to do the same. Also, if I have to send multiple such requests to the server, how would that be possible in Java using a Selenium Framework. Currently, I am opening multiple instances of the framework and running them with different parameters :-(

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• what's wrong with my producer-consumer queue design?

  - by toasteroven

  I'm starting with the C# code example here. I'm trying to adapt it for a couple reasons: 1) in my scenario, all tasks will be put in the queue up-front before consumers will start, and 2) I wanted to abstract the worker into a separate class instead of having raw Thread members within the WorkerQueue class. My queue doesn't seem to dispose of itself though, it just hangs, and when I break in Visual Studio it's stuck on the _th.Join() line for WorkerThread #1. Also, is there a better way to organize this? Something about exposing the WaitOne() and Join() methods seems wrong, but I couldn't think of an appropriate way to let the WorkerThread interact with the queue. Also, an aside - if I call q.Start(#) at the top of the using block, only some of the threads every kick in (e.g. threads 1, 2, and 8 process every task). Why is this? Is it a race condition of some sort, or am I doing something wrong? using System; using System.Collections.Generic; using System.Text; using System.Messaging; using System.Threading; using System.Linq; namespace QueueTest { class Program { static void Main(string[] args) { using (WorkQueue q = new WorkQueue()) { q.Finished += new Action(delegate { Console.WriteLine("All jobs finished"); }); Random r = new Random(); foreach (int i in Enumerable.Range(1, 10)) q.Enqueue(r.Next(100, 500)); Console.WriteLine("All jobs queued"); q.Start(8); } } } class WorkQueue : IDisposable { private Queue _jobs = new Queue(); private int _job_count; private EventWaitHandle _wh = new AutoResetEvent(false); private object _lock = new object(); private List _th; public event Action Finished; public WorkQueue() { } public void Start(int num_threads) { _job_count = _jobs.Count; _th = new List(num_threads); foreach (int i in Enumerable.Range(1, num_threads)) { _th.Add(new WorkerThread(i, this)); _th[_th.Count - 1].JobFinished += new Action(WorkQueue_JobFinished); } } void WorkQueue_JobFinished(int obj) { lock (_lock) { _job_count--; if (_job_count == 0 && Finished != null) Finished(); } } public void Enqueue(int job) { lock (_lock) _jobs.Enqueue(job); _wh.Set(); } public void Dispose() { Enqueue(Int32.MinValue); _th.ForEach(th = th.Join()); _wh.Close(); } public int GetNextJob() { lock (_lock) { if (_jobs.Count 0) return _jobs.Dequeue(); else return Int32.MinValue; } } public void WaitOne() { _wh.WaitOne(); } } class WorkerThread { private Thread _th; private WorkQueue _q; private int _i; public event Action JobFinished; public WorkerThread(int i, WorkQueue q) { _i = i; _q = q; _th = new Thread(DoWork); _th.Start(); } public void Join() { _th.Join(); } private void DoWork() { while (true) { int job = _q.GetNextJob(); if (job != Int32.MinValue) { Console.WriteLine("Thread {0} Got job {1}", _i, job); Thread.Sleep(job * 10); // in reality would to actual work here if (JobFinished != null) JobFinished(job); } else { Console.WriteLine("Thread {0} no job available", _i); _q.WaitOne(); } } } } }

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• Java Non-Blocking HTTP Server

  - by Marcus

  I have written an application using embedded Jetty that makes network calls to other services. I presume that the serving threads are idle whilst waiting for the network calls to complete. Is there any way to have a worker thread that switches between requests to perform work that can be done at the current time and then when the network calls return also handle that? A request would be returned when all work has been completed for it. I know this is a common paradigm, and I have used it for non-blocking TCP networking, but I'm unsure as to how to achieve this on a Java HTTP server whilst also waiting on external results. Any links or explanations are appreciated. Thanks

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• Heavy weight and light weight thread

  - by rocker

  What are the Light weight and heavy weight threads in terms of java????

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• Setting current culture with threads in ASP.NET MVC

  - by mare

  Here's an example of SetCulture attribute which inside does something like this: public void OnActionExecuting(ActionExecutingContext filterContext) { string cultureCode = SetCurrentLanguage(filterContext); if (string.IsNullOrEmpty(cultureCode)) return; HttpContext.Current.Response.Cookies.Add( new HttpCookie("Culture", cultureCode) { HttpOnly = true, Expires = DateTime.Now.AddYears(100) } ); filterContext.HttpContext.Session["Culture"] = cultureCode; CultureInfo culture = new CultureInfo(cultureCode); System.Threading.Thread.CurrentThread.CurrentCulture = culture; System.Threading.Thread.CurrentThread.CurrentUICulture = culture; } I was wondering how does this affect a site with multiple users logged on and each one setting their own culture? What is the scope of a thread here with regards to the IIS worker process (w3wp) that the site is running in?

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• Out-Of-Memory while doing Core Data migration

  - by Kamchatka

  Hello, I'm migrating a CoreData model between two versions of an application. I was storing binary data as blobs in the previous version and I want to take them out of the blobs for performance. My issue is that during the migration it seems that Core Data loads everything into memory which leads to Low Memory Warnings and then to my app being killed. Apple documentation suggests the following : http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmCustomizingTheProcess.html#//apple_ref/doc/uid/TP40005510-SW9 However, it seems to rely on the fact that the large objects are applied different mapping. In my case, all the objects are basically the same and the same mapping has to be applied to each of them. I don't see in this case how I could apply their technique. How should I handle a migration with very large objects ?

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• OutOfMemoryException, stack size is huge, large number of threads

  - by Captain Comic

  Hello, I was profiling my .net windows service. I was trying to discover OutOfMemoryException and discovered that my stack size is huge and is growing because the the number of threads keeps growing. Each thread gets 1024 KB on Windows x64 machine. Thus when my app has 754 threads the stack size would be 772 MB. The problem for me is that i don't know where these thread come from. Initially my app has a very limited number of threads and they keep growing with time. I have two suspicions - either these threads are created by WCF or by database connection. My application uses both WCF and datasets. Also I tried to profile my app in Ants do Trace i can see large number of System.ServiceModel.Channels.ClientReliableDuplexSessionChannel and this number is increasing with time. I can see thousands of these objects created. So what I want to know is who is creating threads (tools to discover, profilers) and if it is WCF who is creating these threads.

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• VB.net: Is my Thread Safe List Solution actually safe?

  - by Shiftbit

  I've added teh following Extensions to my Project in order to create a thread safe list: Extensions If I want to conduct a simple operation on my list <Extension()> _ Public Sub Action(Of T)(ByVal list As List(Of T), ByVal action As Action(Of List(Of T))) SyncLock (list) action(list) End SyncLock End Sub If I want to pass it more than one parameter I could simply extend it with more items... <Extension()> _ Public Sub Action(Of T)(ByVal list As List(Of T), ByVal action As Action(Of List(Of T), T), ByVal item As T) SyncLock (list) Action(list, item) End SyncLock End Sub Actions I have created the following Action Examples: Private Sub Read(Of T)(ByVal list As List(Of T)) Console.WriteLine("Read") For Each item As T In list Console.WriteLine(item.ToString) Thread.Sleep(10) Next End Sub and also one that takes a parameter: Private Sub Write(Of T)(ByVal list As List(Of T), ByVal item As T) Thread.Sleep(100) list.Add(item) Console.WriteLine("Write") End Sub Initiating Then in my various threads I will call my Actions with: list.Action(AddressOf Read) or list.Action(AddressOf Write2, 10) Are these Extenxion methods thread safe or do you have other recommendations?

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• Why AutoResetEvent and ManualResetEvent does not support name in the constructor?

  - by Ikaso

  On .NET Framework 2.0 AutoResetEvent and ManualResetEvent inherit from EventWaitHandle. The EventWaitHandle class has 4 different constructors. 3 of the constructors support giving a name to the event. On the other hand both ManualResetEvent and AutoResetEvent do not support naming and provide a single constructor that receives the initialState. I can simply inherit from EventWaitHandle and write my own implementation of those classes that support all the constructor overloads, but I don't like to re-invent the wheel if I do not have to. My questions are: Is there a special problem in naming events? Do you have any idea why Microsoft did not support it? Do you have a proposal better than inheriting from the EventWaitHandle class and calling the appropriate constructor as in the following example? public class MyAutoResetEvent: EventWaitHandle { public MyAutoResetEvent(bool initialState) : base(initialState, EventResetMode.AutoReset) { } public MyAutoResetEvent(bool initialState, string name) : base(initialState, EventResetMode.AutoReset, name) { } public MyAutoResetEvent(bool initialState, string name, out bool createdNew) : base(initialState, EventResetMode.AutoReset, name, out createdNew) { } public MyAutoResetEvent(bool initialState, string name, out bool createdNew, EventWaitHandleSecurity eventSecurity) : base(initialState, EventResetMode.AutoReset, string.Empty, out createdNew, eventSecurity) { } }

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• For Loop help In a Hash Cracker Homework.

  - by aaron burns

  On the homework I am working on we are making a hash cracker. I am implementing it so as to have my cracker. java call worker.java. Worker.java implements Runnable. Worker is to take the start and end of a list of char, the hash it is to crack, and the max length of the password that made the hash. I know I want to do a loop in run() BUT I cannot think of how I would do it so it would go to the given max pasword length. I have posted the code I have so far. Any directions or areas I should look into.... I thought there was a way to do this with a certain way to write the loop but I don't know or can't find the correct syntax. Oh.. also. In main I divide up so x amount of threads can be chosen and I know that as of write now it only works for an even number of the 40 possible char given. package HashCracker; import java.util.*; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class Cracker { // Array of chars used to produce strings public static final char[] CHARS = "abcdefghijklmnopqrstuvwxyz0123456789.,-!".toCharArray(); public static final int numOfChar=40; /* Given a byte[] array, produces a hex String, such as "234a6f". with 2 chars for each byte in the array. (provided code) */ public static String hexToString(byte[] bytes) { StringBuffer buff = new StringBuffer(); for (int i=0; i<bytes.length; i++) { int val = bytes[i]; val = val & 0xff; // remove higher bits, sign if (val<16) buff.append('0'); // leading 0 buff.append(Integer.toString(val, 16)); } return buff.toString(); } /* Given a string of hex byte values such as "24a26f", creates a byte[] array of those values, one byte value -128..127 for each 2 chars. (provided code) */ public static byte[] hexToArray(String hex) { byte[] result = new byte[hex.length()/2]; for (int i=0; i<hex.length(); i+=2) { result[i/2] = (byte) Integer.parseInt(hex.substring(i, i+2), 16); } return result; } public static void main(String args[]) throws NoSuchAlgorithmException { if(args.length==1)//Hash Maker { //create a byte array , meassage digestand put password into it //and get out a hash value printed to the screen using provided methods. byte[] myByteArray=args[0].getBytes(); MessageDigest hasher=MessageDigest.getInstance("SHA-1"); hasher.update(myByteArray); byte[] digestedByte=hasher.digest(); String hashValue=Cracker.hexToString(digestedByte); System.out.println(hashValue); } else//Hash Cracker { ArrayList<Thread> myRunnables=new ArrayList<Thread>(); int numOfThreads = Integer.parseInt(args[2]); int charPerThread=Cracker.numOfChar/numOfThreads; int start=0; int end=charPerThread-1; for(int i=0; i<numOfThreads; i++) { //creates, stores and starts threads. Runnable tempWorker=new Worker(start, end, args[1], Integer.parseInt(args[1])); Thread temp=new Thread(tempWorker); myRunnables.add(temp); temp.start(); start=end+1; end=end+charPerThread; } } } import java.util.*; public class Worker implements Runnable{ private int charStart; private int charEnd; private String Hash2Crack; private int maxLength; public Worker(int start, int end, String hashValue, int maxPWlength) { charStart=start; charEnd=end; Hash2Crack=hashValue; maxLength=maxPWlength; } public void run() { byte[] myHash2Crack_=Cracker.hexToArray(Hash2Crack); for(int i=charStart; i<charEnd+1; i++) { Cracker.numOfChar[i]////// this is where I am stuck. } } }

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• How to fetch data for AutoCompleteTextView in separate thread?

  - by Laimoncijus

  For my AutoCompleteTextView I need to fetch the data from a webservice. As it can take a little time I do not want UI thread to be not responsive, so I need somehow to fetch the data in a separate thread. For example, while fetching data from SQLite DB, it is very easy done with CursorAdapter method - runQueryOnBackgroundThread. I was looking around to other adapters like ArrayAdapter, BaseAdapter, but could not find anything similar... Is there an easy way how to achieve this? I cannot simply use ArrayAdapter directly, as the suggestions list is dynamic - I always fetch the suggestions list depending on user input, so it cannot be pre-fetched and cached for further use... If someone could give some tips or examples on this topic - would be great!

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