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• Race condition during thread start?

  - by user296353

  Hi, I'm running the following code to start my threads, but they don't start as intended. For some reason, some of the threads start with the same objects (and some don't even start). If I try to debug, they start just fine (extra delay added by me clicking F10 to step through the code). These are the functions in my forms app: private void startWorkerThreads() { int numThreads = config.getAllItems().Count; int i = 0; foreach (ConfigurationItem tmpItem in config.getAllItems()) { i++; var t = new Thread(() => WorkerThread(tmpItem, i)); t.Start(); //return t; } } private void WorkerThread(ConfigurationItem cfgItem, int mul) { for (int i = 0; i < 100; i++) { Thread.Sleep(10*mul); } this.Invoke((ThreadStart)delegate() { this.textBox1.Text += "Thread " + cfgItem.name + " Complete!\r\n"; this.textBox1.SelectionStart = textBox1.Text.Length; this.textBox1.ScrollToCaret(); }); } Anyone able to help me out? Cheers!

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• reactor not working when reactor.run is not called in the main thread and installSignalHandlers=Fals

  - by Kalmi

  I'm trying to answer the following question out of personal interest: What is the fastest way to send 100,000 HTTP requests in Python? And this is what I have came up so far, but I'm experiencing something very stange. When installSignalHandlers is True, it just hangs. I can see that the DelayedCall instances are in reactor._newTimedCalls, but processResponse never gets called. When installSignalHandlers is False, it throws an error and works. from twisted.internet import reactor from twisted.web.client import Agent from threading import Semaphore, Thread import time concurrent = 100 s = Semaphore(concurrent) reactor.suggestThreadPoolSize(concurrent) t=Thread( target=reactor.run, kwargs={'installSignalHandlers':True}) t.daemon=True t.start() agent = Agent(reactor) def processResponse(response,url): print response.code, url s.release() def processError(response,url): print "error", url s.release() def addTask(url): req = agent.request('HEAD', url) req.addCallback(processResponse, url) req.addErrback(processError, url) for url in open('urllist.txt'): addTask(url.strip()) s.acquire() while s._Semaphore__value!=concurrent: time.sleep(0.1) reactor.stop() And here is the error that it throws when installSignalHandlers is True: (Note: This is the expected behaviour! The question is why it doesn't work when installSignalHandlers is False.) Traceback (most recent call last): File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 396, in fireEvent DeferredList(beforeResults).addCallback(self._continueFiring) File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 224, in addCallback callbackKeywords=kw) File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 213, in addCallbacks self._runCallbacks() File "/usr/lib/python2.6/dist-packages/twisted/internet/defer.py", line 371, in _runCallbacks self.result = callback(self.result, *args, **kw) --- <exception caught here> --- File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 409, in _continueFiring callable(*args, **kwargs) File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 1165, in _reallyStartRunning self._handleSignals() File "/usr/lib/python2.6/dist-packages/twisted/internet/base.py", line 1105, in _handleSignals signal.signal(signal.SIGINT, self.sigInt) exceptions.ValueError: signal only works in main thread What am I doing wrong and what is the right way? I'm new to twisted.

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• UpdateAllViews() from within a worker thread?

  - by Harvey

  I have a worker thread in a class that is owned by a ChildView. (I intend to move this to the Doc eventually.) When the worker thread completes a task I want all the views to be updated. How can I make a call to tell the Doc to issue an UpdateAllViews()? Or is there a better approach? Thank you. Added by OP: I am looking for a simple solution. The App is running on a single user, single CPU computer and does not need network (or Internet) access. There is nothing to cause a deadlock. I think I would like to have the worker thread post (or send) a message to cause the views to update. Everything I read about threading seems way more complicated than what I need - and, yes, I understand that all those precautions are necessary for applications that are running in multiprocessor, multiuser, client-server systems, etc. But none of those apply in my situation. I am just stuck at getting the right combination of getting the window handle, posting the message and responding to the message in the right functions and classes to compile and function at all.

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• python thread prob after build

  - by Apache

  hi expert, i'm having task to scan wifi at specific interval and send it to the server, i've it in python and its works fine when i run manually, then build it to package and when run there is no progress at all, i already ask this question before at http://stackoverflow.com/questions/2735410/python-scritp-problem-once-build-and-package-it, then, i re-modify my code as below, then i found that thread is not functioning once i build, #!/usr/bin/env python import subprocess,threading,... configFile = open('/opt/Jemapoh_Wifi/config.txt', 'r') url = configFile.readline().strip() intervalTime = configFile.readline().strip() status = configFile.readline().strip() print "url "+url print "intervalTime "+intervalTime print "Status "+status.strip() def getMacAddress(): proc = subprocess.Popen('ifconfig -a wlan0 | grep HWaddr | sed \'/^.*HWaddr */!d; s///;q\'', shell=True, stdout=subprocess.PIPE, ) macAddress = proc.communicate()[0].strip() return macAddress def getTimestamp(): from time import strftime timeStamp = strftime("%Y-%m-%d %H:%M:%S") return timeStamp def scanWifi(): try: print "Scanning..." proc = subprocess.Popen('iwlist scan 2>/dev/null', shell=True, stdout=subprocess.PIPE, ) stdout_str = proc.communicate()[0] stdout_list=stdout_str.split('\n') essid=[] rssi=[] preQuality=[] for line in stdout_list: line=line.strip() match=re.search('ESSID:"(\S+)"',line) if match: essid.append(match.group(1)) match=re.search('Quality=(\S+)',line) if match: preQuality.append(match.group(1)) for qualityConversion in preQuality: qualityConversion = qualityConversion.split()[0].split('/') temp = str(int(round(float(qualityConversion[0]) / float(qualityConversion[1]) * 100))).rjust(2) rssi.append(temp) dataToPost = '{"userId":"' + getMacAddress() + '","timestamp":"' + getTimestamp() + '","wifi":[' for no in range(len(essid)): dataToPost += '{"ssid":"' + essid[no] + '","rssi":"' + rssi[no] + '"}' if no+1 == len(essid): pass else: dataToPost += ',' dataToPost += ']}' query_args = {"data":dataToPost} request = urllib2.Request(url) request.add_data(urllib.urlencode(query_args)) request.add_header('Content-Type', 'application/x-www-form-urlencoded') print "Waiting for server response..." print urllib2.urlopen(request).read() print "Data Sent @ " + getTimestamp() print "------------------------------------------------------" t = threading.Timer(int(intervalTime), scanWifi).start() except Exception, e: print e t = threading.Timer(int(intervalTime), scanWifi) t.start() once build, its not reaching the thread, do can anyone help, why the thread is not working after build thanks

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• InfoPath FormControl on STA worker thread

  - by Rob Ford

  I have a .NET class that exposes two public methods: one to create an InfoPath form and another to Export to one of the supported formats. I’m using the Microsoft FormControl to do this. It’s hosted by a Form that does not get displayed. I get called by a Winforms app, but on an MTA worker thread instead of the UI thread. So I create an STA thread and execute on that, which works exactly once and then results in this exception: System.InvalidOperationException was unhandled Message="Unable to get the window handle for the 'FormControl' control. Windowless ActiveX controls are not supported." Source="System.Windows.Forms" StackTrace: at System.Windows.Forms.AxHost.EnsureWindowPresent() at System.Windows.Forms.AxHost.InPlaceActivate() at System.Windows.Forms.AxHost.TransitionUpTo(Int32 state) at System.Windows.Forms.AxHost.CreateHandle() at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible) at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible) at System.Windows.Forms.AxHost.EndInit() at InfoPathCreateStaThreadTest.FormControlHost.InitializeComponent() in C:\Windows\Temp\InfoPathCreateStaThreadTest\InfoPathCreateStaThreadTest\FormControlHost.Designer.cs:line 65 After some experimenting, I started to suspect this is a message pumping problem. I then came across this, which makes me more strongly suspect so: http://blogs.msdn.com/cbrumme/archive/2004/02/02/66219.aspx I tried various methods of pumping messages with no luck. I should mention that the alternative of automating the InfoPath app is not viable unless I can figure out how to hide the app. Any help would be much appreciated.

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• Performance Difference between HttpContext user and Thread user

  - by atrueresistance

  I am wondering what the difference between HttpContext.Current.User.Identity.Name.ToString.ToLower and Thread.CurrentPrincipal.Identity.Name.ToString.ToLower. Both methods grab the username in my asp.net 3.5 web service. I decided to figure out if there was any difference in performance using a little program. Running from full Stop to Start Debugging in every run. Dim st As DateTime = DateAndTime.Now Try 'user = HttpContext.Current.User.Identity.Name.ToString.ToLower user = Thread.CurrentPrincipal.Identity.Name.ToString.ToLower Dim dif As TimeSpan = Now.Subtract(st) Dim break As String = "nothing" Catch ex As Exception user = "Undefined" End Try I set a breakpoint on break to read the value of dif. The results were the same for both methods. dif.Milliseconds 0 Integer dif.Ticks 0 Long Using a longer duration, loop 5,000 times results in these figures. Thread Method run 1 dif.Milliseconds 125 Integer dif.Ticks 1250000 Long run 2 dif.Milliseconds 0 Integer dif.Ticks 0 Long run 3 dif.Milliseconds 0 Integer dif.Ticks 0 Long HttpContext Method run 1 dif.Milliseconds 15 Integer dif.Ticks 156250 Long run 2 dif.Milliseconds 156 Integer dif.Ticks 1562500 Long run 3 dif.Milliseconds 0 Integer dif.Ticks 0 Long So I guess what is more prefered, or more compliant with webservice standards? If there is some type of a performance advantage, I can't really tell. Which one scales to larger environments easier?

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• Set HttpContext.Current.User from Thread.CurrentPrincipal

  - by Argons

  I have a security manager in my application that works for both windows and web, the process is simple, just takes the user and pwd and authenticates them against a database then sets the Thread.CurrentPrincipal with a custom principal. For windows applications this works fine, but I have problems with web applications. After the process of authentication, when I'm trying to set the Current.User to the custom principal from Thread.CurrentPrincipal this last one contains a GenericPrincipal. Am I doing something wrong? This is my code: Login.aspx protected void btnAuthenticate_Click(object sender, EventArgs e) { Authenticate("user","pwd"); FormsAuthenticationTicket authenticationTicket = new FormsAuthenticationTicket(1, "user", DateTime.Now, DateTime.Now.AddMinutes(30), false, ""); string ticket = FormsAuthentication.Encrypt(authenticationTicket); HttpCookie authenticationCookie = new HttpCookie(FormsAuthentication.FormsCookieName, ticket); Response.Cookies.Add(authenticationCookie); Response.Redirect(FormsAuthentication.GetRedirectUrl("user", false)); } Global.asax (This is where the problem appears) protected void Application_AuthenticateRequest(object sender, EventArgs e) { HttpCookie authCookie = Context.Request.Cookies[FormsAuthentication.FormsCookieName]; if (authCookie == null) return; if (HttpContext.Current.User != null && HttpContext.Current.User.Identity.IsAuthenticated && HttpContext.Current.User.Identity is FormsIdentity) { HttpContext.Current.User = System.Threading.Thread.CurrentPrincipal; //Here the value is GenericPrincipal } Thanks in advance for any help. }

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• problem in working with thread

  - by Xaver

  Ihave the tree view in which i have file system of logical disk. When user select some files and folders and press button programm evaluate the size of selected files and folders. this function may takes a long time. i decide do thread which will run this function. This function works with array of TreeNode. but then i want to now was it node expaned or not compiler say: "attempt to access control "treeview1" not from the thread, in which it was created." Why it appeared? Next code is show how i create array of Nodes which i send to new thread: void frmMain::FillSelected(TreeNode^ a, array<TreeNode^>^ *Paths) { if (a->Parent == nullptr) { for(int j = 0;j < a->Nodes->Count;j++) { if ((a->Nodes[j]->ImageIndex == 1)&&(a->Nodes[j]->Checked==true)) { (*Paths)->Resize((*Paths), (*Paths)->Length + 1); (*Paths)[(*Paths)->Length-1] = a->Nodes[j]; } } } for(int i = 0;i < a->Nodes->Count;i++) { if (a->Parent == nullptr) { FillSelected(a->Nodes[i], Paths); } else { if(a->Nodes[i]->Checked == true) { (*Paths)->Resize((*Paths), (*Paths)->Length + 1); (*Paths)[(*Paths)->Length-1] = a->Nodes[i]; } if ((a->Nodes[i]->Nodes->Count > 0)&&(a->Nodes[i]->Nodes[0]->FullPath != (a->Nodes[i]->FullPath + "\\"))) { FillSelected(a->Nodes[i], Paths); } } } return; }

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• [Cocoa] Placing an NSTimer in a separate thread

  - by ndg

  I'm trying to setup an NSTimer in a separate thread so that it continues to fire when users interact with the UI of my application. This seems to work, but Leaks reports a number of issues - and I believe I've narrowed it down to my timer code. Currently what's happening is that updateTimer tries to access an NSArrayController (timersController) which is bound to an NSTableView in my applications interface. From there, I grab the first selected row and alter its timeSpent column. From reading around, I believe what I should be trying to do is execute the updateTimer function on the main thread, rather than in my timers secondary thread. I'm posting here in the hopes that someone with more experience can tell me if that's the only thing I'm doing wrong. Having read Apple's documentation on Threading, I've found it an overwhelmingly large subject area. NSThread *timerThread = [[[NSThread alloc] initWithTarget:self selector:@selector(startTimerThread) object:nil] autorelease]; [timerThread start]; -(void)startTimerThread { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSRunLoop *runLoop = [NSRunLoop currentRunLoop]; activeTimer = [[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateTimer:) userInfo:nil repeats:YES] retain]; [runLoop run]; [pool release]; } -(void)updateTimer:(NSTimer *)timer { NSArray *selectedTimers = [timersController selectedObjects]; id selectedTimer = [selectedTimers objectAtIndex:0]; NSNumber *currentTimeSpent = [selectedTimer timeSpent]; [selectedTimer setValue:[NSNumber numberWithInt:[currentTimeSpent intValue]+1] forKey:@"timeSpent"]; } -(void)stopTimer { [activeTimer invalidate]; [activeTimer release]; }

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• Performing selectors on main thread with NSInvocation

  - by kpower

  I want to perform animation on main thread (cause UIKit objects are not thread-safe), but prepare it in some separate thread. I have (baAnimation - is CABasicAnimation allocated & inited before): SEL animationSelector = @selector(addAnimation:forKey:); NSString *keyString = @"someViewAnimation"; NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[workView.layer methodSignatureForSelector:animationSelector]]; [inv setTarget:workView.layer]; [inv setSelector:animationSelector]; [inv setArgument:baAnimation atIndex:2]; [inv setArgument:keyString atIndex:3]; [inv performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:NO]; I get: *** +[NSCFString length]: unrecognized selector sent to class 0x1fb36a0 Calls: > #0 0x020984e6 in objc_exception_throw > #1 0x01f7e8fb in +[NSObject doesNotRecognizeSelector:] > #2 0x01f15676 in ___forwarding___ > #3 0x01ef16c2 in __forwarding_prep_0___ > #4 0x01bb3c21 in -[CALayer addAnimation:forKey:] > #5 0x01ef172d in __invoking___ > #6 0x01ef1618 in -[NSInvocation invoke] But [workView.layer addAnimation:baAnimation forKey:@"someViewAnimation"]; works fine. What am I doing wrong?

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• Creating WPF components in background thread

  - by mizipzor

  Im working on a reporting system, a series of DocumentPage are to be created through a DocumentPaginator. These documents include a number of WPF components that are to be instantiated so the paginator includes the correct things when later sent to the XpsDocumentWriter (which in turn is sent to the actual printer). My problem now is that the DocumentPage instances take quite a while to create (enough for Windows to mark the application as frozen) so I tried to create them in a background thread, which is problematic since WPF expects the attributes on them to be set from the GUI thread. I would also like to have a progress bar showing up, indicating how many pages have been created so far. Thus, it looks like Im trying to get two things to happen in parallell on the GUI. The problem is hard to explain and Im really not sure how to tackle it. In short: Create a series of DocumentPage's. These include WPF components These are to be created on a background thread, or use some other trick so the application isnt frozen. After each page is created, a WPF ProgressBar should be updated. If there is no decent way to do this, alternate solutions and approaches are more than welcome.

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• Spawning a thread in python

  - by morpheous

  I have a series of 'tasks' that I would like to run in separate threads. The tasks are to be performed by separate modules. Each containing the business logic for processing their tasks. Given a tuple of tasks, I would like to be able to spawn a new thread for each module as follows. from foobar import alice, bob charles data = getWorkData() # these are enums (which I just found Python doesn't support natively) :( tasks = (alice, bob, charles) for task in tasks # Ok, just found out Python doesn't have a switch - @#$%! # yet another thing I'll need help with then ... switch case alice: #spawn thread here - how ? alice.spawnWorker(data) No prizes for guessing I am still thinking in C++. How can I write this in a Pythonic way using Pythonic 'enums' and 'switch'es, and be able to run a module in a new thread. Obviously, the modules will all have a class that is derived from a ABC (abstract base class) called Plugin. The spawnWorker() method will be declared on the Plugin interface and defined in the classes implemented in the various modules. Maybe, there is a better (i.e. Pythonic) way of doing all this?. I'd be interested in knowing

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• Thread loses Message after wait() and notify()

  - by fugu2.0

  Hey Guys! I have a problem handling messages in a Thread. My run-method looks like this public void run() { Looper.prepareLooper(); parserHandler = new Handler { public void handleMessage(Message msg) { Log.i("","id from message: "+msg.getData.getString("id")); // handle message this.wait(); } } } I have several Activities sending messages to this thread, like this: Message parserMessage = new Message(); Bundle data = new Bundle(); data.putString("id", realId); data.putString("callingClass", "CategoryList"); parserMessage.setData(data); parserMessage.what = PARSE_CATEGORIES_OR_PRODUCTS; parserHandler = parser.getParserHandler(); synchronized (parserHandler) { parserHandler.notify(); Log.i("","message ID: " + parserMessage.getData().getString("id")); } parserHandler.sendMessage(parserMessage); The problem is that the run-method logs "id from message: null" though "message ID" has a value in the Log-statement. Why does the message "lose" it's data when being send to the thread? Has it something to do with the notify? Thanks for your help

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• Thread Locking CollectionViewSource

  - by Robert

  I added an event handler to my code and it broke all access to the CollectionViewSources in the SystemHTA class saying "The calling thread cannot access this object because a different thread owns it". My class was working when "this.systemHTA = new SystemHTA();" was placed outside of the DeviceManager_StateChanged() function. public partial class MainWindow : Window { private DeviceManager DeviceManager = DeviceManager.Instance; public SystemHTA systemHTA; public MainWindow() { InitializeComponent(); } private void Window_Loaded(object sender, RoutedEventArgs e) { DeviceManager.StateChanged += new EventHandler<DeviceManagerStateChangedEventArgs>(DeviceManager_StateChanged); DeviceManager.Initialize(); } void DeviceManager_StateChanged(object sender, DeviceManagerStateChangedEventArgs e) { if (e.State == DeviceManagerState.Operational) { this.systemHTA = new SystemHTA(); } } private void button1_Click(object sender, RoutedEventArgs e) { this.systemHTA.GetViewSourceTest(); } } public class SystemHTA { private CollectionViewSource _deviceTestSource; public SystemHTA() { _deviceTestSource = new CollectionViewSource(); _deviceTestSource.Source = CreateLoadData<HWController>.ControllerCollection; } public void GetViewSourceTest() { ListCollectionView view = (ListCollectionView)_deviceTestSource.View; //This creates an error saying a thread already owns _deviceTestSource } }

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• Boost::Thread linking error on OSX?

  - by gct

  So I'm going nuts trying to figure this one out. Here's my basic setup: I'm compiling a shared library with a bunch of core functionality that uses a lot of boost stuff. We'll call this library libpf_core.so. It's linked with the boost static libraries, specifically the python, system, filesystem, thread, and program_options libraries. This all goes swimmingly. Now, I have a little test program called test_socketio which is compiled into a shared library (it's loaded as a plugin at runtime). It uses some boost stuff like boost::bind and boost::thread, and it's linked again libpf_core.so (which has the boost libraries included remember). When I go to compile test_socketio though, out of all my plugins it gives me a linking error: [ Building test_socketio ] g++ -c -pg -g -O0 -I/usr/local/include -I../include test_socketio.cc -o test_socketio.o g++ -shared test_socketio.o -lpy_core -o test_socketio.so Undefined symbols: "boost::lock_error::lock_error()", referenced from: boost::unique_lock<boost::mutex>::lock() in test_socketio.o ld: symbol(s) not found collect2: ld returned 1 exit status And I'm going crazy trying to figure out why this is. I've tried explicitly linking boost::thread into the plugin to no avail, tried ensuring that I'm using the boost headers associated with the libraries linked into libpf_core.so in case there was a conflict there. Is there something OSX specific regarding boost that I'm missing? In my searching on google I've seen a number of other people get this error but no one seems to have come up with a satisfactory solution.

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• creating QT gui using a thread in c++?

  - by rashid

  I am trying to create this QT gui using a thread but no luck. Below is my code. Problem is gui never shows up. /*INCLUDES HERE... .... */ using namespace std; struct mainStruct { int s_argc;<br> char ** s_argv; }; typedef struct mainStruct mas; void *guifunc(void * arg); int main(int argc, char * argv[]) { mas m;<br> m.s_argc = argc;<br> m.s_argv = argv;<br> pthread_t threadGUI; //start a new thread for gui int result = pthread_create(&threadGUI, NULL, guifunc, (void *) &m); if (result) {<br> printf("Error creating gui thread"); exit(0); } return 0; } void *guifunc(void * arg) { mas m = *(mas *)arg; QApplication app(m.s_argc,m.s_argv); //object instantiation<br> guiClass *gui = new guiClass(); //show gui<br> gui->show(); app.exec(); <br> }

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• Debugging instance of another thread altering my data

  - by Mick

  I have a huge global array of structures. Some regions of the array are tied to individual threads and those threads can modify their regions of the array without having to use critical sections. But there is one special region of the array which all threads may have access to. The code that accesses these parts of the array needs to carefully use critical sections (each array element has its own critical section) to prevent any possibility of two threads writing to the structure simultaneously. Now I have a mysterious bug I am trying to chase, it is occurring unpredictably and very infrequently. It seems that one of the structures is being filled with some incorrect number. One obvious explanation is that another thread has accidentally been allowed to set this number when it should be excluded from doing so. Unfortunately it seems close to impossible to track this bug. The array element in which the bad data appears is different each time. What I would love to be able to do is set some kind of trap for the bug as follows: I would enter a critical section for array element N, then I know that no other thread should be able to touch the data, then (until I exit the critical section) set some kind of flag to a debugging tool saying "if any other thread attempts to change the data here please break and show me the offending patch of source code"... but I suspect no such tool exists... or does it? Or is there some completely different debugging methodology that I should be employing.

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• boost thread pool

  - by Dtag

  I need a threadpool for my application, and I'd like to rely on standard (C++11 or boost) stuff as much as possible. I realize there is an unofficial(!) boost thread pool class, which basically solves what I need, however I'd rather avoid it because it is not in the boost library itself -- why is it still not in the core library after so many years? In some posts on this page and elsewhere, people suggested using boost::asio to achieve a threadpool like behavior. At first sight, that looked like what I wanted to do, however I found out that all implementations I have seen have no means to join on the currently active tasks, which makes it useless for my application. To perform a join, they send stop signal to all the threads and subsequently join them. However, that completely nullifies the advantage of threadpools in my use case, because that makes new tasks require the creation of a new thread. What I want to do is: ThreadPool pool(4); for (...) { for (int i=0;i<something;i++) pool.pushTask(...); pool.join(); // do something with the results } Can anyone suggest a solution (except for using the existing unofficial thread pool on sourceforge)? Is there anything in C++11 or core boost that can help me here? Thanks a lot

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• Servlet that starts a thread only once for every visitor

  - by user858749

  Hey I want to implement a Java Servlet that starts a thread only once for every single user. Even on refresh it should not start again. My last approach brought me some trouble so no code^^. Any Suggestions for the layout of the servlet? public class LoaderServlet extends HttpServlet { // The thread to load the needed information private LoaderThread loader; // The last.fm account private String lfmaccount; public LoaderServlet() { super(); lfmaccount = ""; } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if (loader != null) { response.setContentType("text/plain"); response.setHeader("Cache-Control", "no-cache"); PrintWriter out = response.getWriter(); out.write(loader.getStatus()); out.flush(); out.close(); } else { loader = new LoaderThread(lfmaccount); loader.start(); request.getRequestDispatcher("WEB-INF/pages/loader.jsp").forward( request, response); } } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if (lfmaccount.isEmpty()) { lfmaccount = request.getSession().getAttribute("lfmUser") .toString(); } request.getRequestDispatcher("WEB-INF/pages/loader.jsp").forward( request, response); } } The jsp uses ajax to regularly post to the servlet and get the status. The thread just runs like 3 minutes, crawling some last.fm data.

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• Pointer inside a struct / thread

  - by bruno

  Hi! I have this warning "warning: assignment from incompatible pointer type " in this line: data1->transformed_block[l] = &transformed_block[l]; - void print_message_function ( void *ptr ) { dt *data; data = (dt *) ptr; printf("Dentro da thread Numero0: %ld\n", data->L_norm_NewBlock); pthread_exit(0); } typedef struct data_thread { long L_norm_NewBlock; int Bsize_X; int Bsize_Y; int *transformed_block[MAX_LEVEL]; long L_norm_OrigBlock; } dt; void function() { int *transformed_block[MAX_LEVEL]; pthread_t thread1; dt *data1; pthread_attr_t attr; pthread_attr_init(&attr); //Fills structure data1 = (dt *) malloc(sizeof(dt)); data1->transformed_block[l] = &transformed_block[l]; data1->L_norm_NewBlock=0; data1->Bsize_Y = Bsize_Y; data1->Bsize_X = Bsize_X; pthread_create(&thread1, &attr, (void *) &print_message_function, (void *) &data1); } I want to get rid of that warning, and the values i get inside the thread are wrong. For example data1-L_norm_NewBlock=0; in the thread guives me a differente value (not 0 like it should be).

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• Get the first and last posts in a thread

  - by Grampa

  I am trying to code a forum website and I want to display a list of threads. Each thread should be accompanied by info about the first post (the "head" of the thread) as well as the last. My current database structure is the following: threads table: id - int, PK, not NULL, auto-increment name - varchar(255) posts table: id - int, PK, not NULL, auto-increment thread_id - FK for threads The tables have other fields as well, but they are not relevant for the query. I am interested in querying threads and somehow JOINing with posts so that I obtain both the first and last post for each thread in a single query (with no subqueries). So far I am able to do it using multiple queries, and I have defined the first post as being: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id LIMIT 0, 1 The last post is pretty much the same except for ORDER BY id DESC. Now, I could select multiple threads with their first or last posts, by doing: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id GROUP BY t.id But of course I can't get both at once, since I would need to sort both ASC and DESC at the same time. What is the solution here? Is it even possible to use a single query? Is there any way I could change the structure of my tables to facilitate this? If this is not doable, then what tips could you give me to improve the query performance in this particular situation?

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• how to edit controls in a system::thread

  - by Ian Lundberg

  I need to be able to add items to a listbox inside of a thread. Code is below. 1. ref class Work 2. { 3. public: 4. static void RecieveThread() 5. { 6. while (true) 7. { 8. ZeroMemory(cID, 64); 9. ZeroMemory(message, 256); 10. if(recv(sConnect, message, 256, NULL) != SOCKET_ERROR && recv(sConnect, cID, 64, NULL) != SOCKET_ERROR) 11. { 12. ID = atoi(cID); 13. String^ meep = gcnew String(message); 14. lbxMessages->Items->Add(meep); 15. check = 1; 16. } 17. } 18. } 19. }; I get the error Error: a nonstatic member reference must be relative to a specific object on line 14. Is there any way to get it to let me do that? Because if I try to use String^ meep; outside of that Thread it doesn't contain anything. It works PERFECT when I use it within the thread but not outside of it. I need to be able to add that message to the listbox. If anyone can help I would appreciate it.

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• sqlobject: No connection has been defined for this thread or process

  - by Claudiu

  I'm using sqlobject in Python. I connect to the database with conn = connectionForURI(connStr) conn.makeConnection() This succeeds, and I can do queries on the connection: g_conn = conn.getConnection() cur = g_conn.cursor() cur.execute(query) res = cur.fetchall() This works as intended. However, I also defined some classes, e.g: class User(SQLObject): class sqlmeta: table = "gui_user" username = StringCol(length=16, alternateID=True) password = StringCol(length=16) balance = FloatCol(default=0) When I try to do a query using the class: User.selectBy(username="foo") I get an exception: ... File "c:\python25\lib\site-packages\SQLObject-0.12.4-py2.5.egg\sqlobject\main.py", line 1371, in selectBy conn = connection or cls._connection File "c:\python25\lib\site-packages\SQLObject-0.12.4-py2.5.egg\sqlobject\dbconnection.py", line 837, in __get__ return self.getConnection() File "c:\python25\lib\site-packages\SQLObject-0.12.4-py2.5.egg\sqlobject\dbconnection.py", line 850, in getConnection "No connection has been defined for this thread " AttributeError: No connection has been defined for this thread or process How do I define a connection for a thread? I just realized I can pass in a connection keyword which I can give conn to to make it work, but how do I get it to work if I weren't to do that?

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• Is this function thread-safe?

  - by kiddo

  Hello all,I am learning multi-threading and for the sake of understanding I have wriiten a small function using multithreading...it works fine.But I just want to know if that thread is safe to use,did I followed the correct rule. void CThreadingEx4Dlg::OnBnClickedOk() { //in thread1 100 elements are copied to myShiftArray(which is a CStringArray) thread1 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction1,this); WaitForSingleObject(thread1->m_hThread,INFINITE); //thread2 waits for thread1 to finish because thread2 is going to make use of myShiftArray(in which thread1 processes it first) thread2 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction2,this); thread3 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction3,this); } UINT MyThreadFunction1(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; pthis->MyFunction(0,100); return 0; } UINT MyThreadFunction2(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; pthis->MyCommonFunction(0,20); return 0; } UINT MyThreadFunction3(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; WaitForSingleObject(pthis->thread3->m_hThread,INFINITE); //here thread3 waits for thread 2 to finish so that thread can continue pthis->MyCommonFunction(21,40); return 0; } void CThreadingEx4Dlg::MyFunction(int minCount,int maxCount) { for(int i=minCount;i<maxCount;i++) { //assume myArray is a CStringArray and it has 100 elemnts added to it. //myShiftArray is a CStringArray -public to the class CString temp; temp = myArray.GetAt(i); myShiftArray.Add(temp); } } void CThreadingEx4Dlg::MyCommonFunction(int min,int max) { for(int i = min;i < max;i++) { CSingleLock myLock(&myCS,TRUE); CString temp; temp = myShiftArray.GetAt(i); //threadArray is CStringArray-public to the class threadArray.Add(temp); } myEvent.PulseEvent(); }

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• Is the below thread pool implementation correct(C#3.0)

  - by Newbie

  Hi Experts, For the first time ever I have implemented thread pooling and I found it to be working. But I am not very sure about the way I have done is the appropriate way it is supposed to be. Would you people mind in spending some valuable time to check and let me know if my approach is correct or not? If you people find that the approach is incorrect , could you please help me out in writing the correct version. I have basicaly read How to use thread pool and based on what ever I have understood I have developed the below program as per my need public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion }

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