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• My python program always brings down my internet connection after several hours running, how do I debug and fix this problem?

  - by Shane

  I'm writing a python script checking/monitoring several server/websites status(response time and similar stuff), it's a GUI program and I use separate thread to check different server/website, and the basic structure of each thread is using an infinite while loop to request that site every random time period(15 to 30 seconds), once there's changes in website/server each thread will start a new thread to do a thorough check(requesting more pages and similar stuff). The problem is, my internet connection always got blocked/jammed/messed up after several hours running of this script, the situation is, from my script side I got urlopen error timed out each time it's requesting a page, and from my FireFox browser side I cannot open any site. But the weird thing is, the moment I close my script my Internet connection got back on immediately which means now I can surf any site through my browser, so it must be the script causing all the problem. I've checked the program carefully and even use del to delete any connection once it's used, still get the same problem. I only use urllib2, urllib, mechanize to do network requests. Anybody knows why such thing happens? How do I debug this problem? Is there a tool or something to check my network status once such situation occurs? It's really bugging me for a while... By the way I'm behind a VPN, does it have something to do with this problem? Although I don't think so because my network always get back on once the script closed, and the VPN connection never drops(as it appears) during the whole process.

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• Are C++ Reads and Writes of an int atomic

  - by theschmitzer

  I have two threads, one updating an int and one reading it. This value is a statistic where the order of the read and write is irrelevant. My question is, do I need to synchronize access to this multi-byte value anyway? Or, put another way, can part of the write be complete and get interrupted, and then the read happen. For example, think of value = ox0000FFFF increment value to 0x00010000 Is there a time where the value looks like 0x0001FFFF that I should be worried about? Certainly the larger the type, the more possible something like this is I've always synchronized these types of accesses, but was curious what the community thought.

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• Is EndInvoke() optional, sort-of optional, or definitely not optional?

  - by endian

  I've read conflicting opinions as to whether every BeginInvoke() has to be matched by an EndInvoke(). Are there any leaks or other problems associated with NOT calling EndInvoke()?

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• How can I set a breakpoint on _NSLockError()

  - by Sheehan Alam

  I am trying to debug multiple threads. *** -[NSLock lock]: deadlock (<NSLock: 0xc388ab0> '(null)') *** Break on _NSLockError() to debug. How can I debug this?

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• How to call a function though Control.BeginInvoke in a signal-slot-like fashion?

  - by Dimitri C.

  I'd like a delegate that calls a function in a different thread when it is invoked. Currently, I'm using the following implementation: delegate void someFunctionDelegate(); //... someFunctionDelegate callBackFunction = someForm.SomeFunction; someForm.Invoke(someFunctionDelegate); However, I'd like a more compact form, combining both the someForm instance and the SomeForm.SomeFunction member function. I'm thinking of something like this: var callBackFunction = new AsynchronousCrossThreadDelegate(someForm, SomeForm.SomeFunction); callBackFunction(); // Should call someForm.BeginInvoke(SomeForm.SomeFunction); Is there a way to do so in C#/.NET? Update I'm looking for a solution that will work for functions with 0 or more parameters.

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• Pattern for iPhone background loading during init?

  - by Rob S.

  Hi everyone, I'm currently kicking off a background thread to do some REST queries in my app delegate's didFinishLaunchingWithOptions. This thread creates some objects and populates the model as the rest of the app continues to load (because I don't block, and didFinishLaunchingWithOptions returns YES). I also put up a loading UIViewController 'on top' of the main view that I tear down after the background initialization is complete. My problem is that I need to notify the first view (call it the Home view) that the model is ready, and that it should populate itself. The trick is that the background download could have finished before Home.viewDidAppear is called, or any of the other Home.initX methods. I'm having difficulty synchronizing all of this and I've thought about it long enough that it feels like I'm barking up the wrong tree. Are there any patterns here for this sort of thing? I'm sure other apps start by performing lengthy operations with loading screens :) Thanks!

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• Clarification on Threads and Run Loops In Cocoa

  - by dubbeat

  I'm trying to learn about threading and I'm thoroughly confused. I'm sure all the answers are there in the apple docs but I just found it really hard to breakdown and digest. Maybe somebody could clear a thing or 2 up for me. 1)performSelectorOnMainThread Does the above simply register an event in the main run loop or is it somehow a new thread even though the method says "mainThread"? If the purpose of threads is to relieve processing on the main thread how does this help? 2) RunLoops Is it true that if I want to create a completely seperate thread I use "detachNewThreadSelector"? Does calling start on this initiate a default run loop for the thread that has been created? If so where do run loops come into it? 3) And Finally , I've seen examples using NSOperationQueue. Is it true to say that If you use performSelectorOnMainThread the threads are in a queue anyway so NSOperation is not needed? 4) Should I forget about all of this and just use the Grand Central Dispatch instead?

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• Implement a threading to prevent UI block on a bug in an async function

  - by Marcx

  I think I ran up againt a bug in an async function... Precisely the getDirectoryListingAsync() of the File class... This method is supposted to return an object containing the lists of files in a specified folder. I found that calling this method on a direcory with a lot of files (in my tests more than 20k files), after few seconds there is a block on the UI until the process is completed... I think that this method is separated in two main block: 1) get the list of files 2) create the array with the details of the files The point 1 seems to be async (for a few second the ui is responsive), then when the process pass from point 1 to point 2 the block of the UI occurs until the complete event is dispathed... Here's some (simple) code: private function checkFiles(dir:File):void { if (dir.exists) { dir.addEventListener( FileListEvent.DIRECTORY_LISTING, listaImmaginiLocale); dir.getDirectoryListingAsync(); // after this point, for the firsts seconds the UI respond well (point 1), // few seconds later (point 2) the UI is frozen } } private function listaImmaginiLocale( event:FileListEvent ):void { // from this point on the UI is responsive again... } Actually in my projects there are some function that perform an heavy cpu usage and to prevent the UI block I implemented a simple function that after some iteration will wait giving time to UI to be refreshed. private var maxIteration:int = 150000; private function sampleFunct(offset:int = 0) :void { if (offset < maxIteration) { // do something // call the recursive function using a timeout.. // if the offset in multiple by 1000 the function will wait 15 millisec, // otherwise it will be called immediately // 1000 is a random number for the pourpose of this example, but I usually change the // value based on how much heavy is the function itself... setTimeout(function():void{aaa(++offset);}, (offset%1000?15:0)); } } Using this method I got a good responsive UI without afflicting performance... I'd like to implement it into the getDirectoryListingAsync method but I don't know if it's possibile how can I do it where is the file to edit or extend.. Any suggestion???

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• how to differentiate between two threads

  - by mithun1538

  Hello everyone, I have the following code in my program: Thread getUsersist, getChatUsers; getUsersList = new Thread(this, "getOnlineUsers"); getUsersList.start(); getChatUsers = new Thread(this, "getChatUsers"); getChatUsers.start(); In run(), I wish to know which thread is using run(). If its "getOnlineUsers" i will do something, If it is "getChatUsers" I will do something else. So how do I know which thread is using run()?

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• Cocoa multhithreads, locks don't work

  - by Igor

  I have a threadMethod which shows in console robotMotorsStatus every 0.5 sec. But when I try to change robotMotorsStatus in changeRobotStatus method I receive an exception. Where I need to put locks in that program. #import "AppController.h" @implementation AppController extern char *robotMotorsStatus; - (IBAction)runThread:(id)sender { [self performSelectorInBackground:@selector(threadMethod) withObject:nil]; } - (void)threadMethod { char string_to_send[]="QFF001100\r"; //String prepared to the port sending (first inintialization) string_to_send[7] = robotMotorsStatus[0]; string_to_send[8] = robotMotorsStatus[1]; while(1){ [theLock lock]; usleep(500000); NSLog (@"Robot status %s", robotMotorsStatus); [theLock unlock]; } } - (IBAction)changeRobotStatus:(id)sender { robotMotorsStatus[0]='1'; }

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• Background thread in .NET

  - by Xodarap

  When the user saves some data, I want to spin off a background thread to update my indexes and do some other random stuff. Even if there is an error in this indexing the user can't do anything about it, so there is no point in forcing the main thread to wait until the background thread finishes. I'm doing this from a ASP.NET process, so I think I should be able to do this (as the main thread exiting won't kill the process). When I set a breakpoint in the background thread's method though, the main thread also appears to stop. Is this just an artifact of visual studio's debugger, or is the main thread really not going to return until the background thread stops?

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• SQL Compact Edition 3.5 SP 1 - LockTimeOutException - how to debug?

  - by Bob King

  Intermittently in our app, we encounter LockTimeoutExceptions being throw from SQL CE. We've recently upgraded to 3.5 SP 1, and a number of them seem to have gone away, but we still do see them occasionally. I'm certain it's a bug in our code (which is multi-threaded) but I haven't been able to pin it down precisely. Does anyone have any good techniques for debugging this problem? The exceptions log like this (there's never a stack trace for these exceptions): SQL Server Compact timed out waiting for a lock. The default lock time is 2000ms for devices and 5000ms for desktops. The default lock timeout can be increased in the connection string using the ssce: default lock timeout property. [ Session id = 6,Thread id = 7856,Process id = 10116,Table name = Product,Conflict type = s lock (x blocks),Resource = DDL ] Our database is read-heavy, but does seldom writes, and I think I've got everything protected where it needs to be. EDIT: SQL CE already automatically uses NOLOCK http://msdn.microsoft.com/en-us/library/ms172398(sql.90).aspx

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• C++ thread to separate process

  - by silverbandit91

  Is there any way I can have a thread branch off into its own independent process? I know there's the CreateProcess function but as far as I can tell, you can only run external applications with it. Is what I'm asking for at all possible?

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• logging one thread in Java using log4j

  - by Javier

  I have an web application written in Java, and I have a thread-pool. The application is huge, and I cannot make major changes, for example, I cannot change log4j. I am executing a batch process in the thread pool, and I want to log everything that goes is executed to execute that process. There will always be just one thread active in the thread pool. Any ideas of how can I do that?

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• java statistics collection for performance evaluation

  - by user384706

  What is the most efficient way to collect and report performance statistic analysis from an application? If I have an application that uses a series of network apis, and I want to report statistics at runtime, e.g. Method doA() was called 3 times and consumed on avg 500ms Method doB() was called 5 times and consumed on avg 1200ms etc Then, I thought of using a well defined data structure (of collection) that each thread updates per remote call, and this can be used for the report. But I think that it will make the performance worse, for the time spend for statistics collection. Am I correct? How would I procceed if I used a background thread for this, and the other threads that did the remote calls were unaware of this collection gathering? Thanks

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• How do I stop Ant from hanging after executing a java program that attempted to interrupt a thread (and failed) and continued?

  - by Zugwalt

  I have Ant build and execute a java program. This program tries to do something that sometimes hangs, so we execute it in a thread. actionThread.start(); try { actionThread.join(10000); } catch (InterruptedException e) { System.out.println("InterruptedException: "+e.getMessage()); } if (actionThread.isAlive()) { actionThread.interrupt(); System.out.println("Thread timed out and never died"); } The ant call looks like this: <java fork="true" failonerror="yes" classname="myPackage.myPathName" classpath="build"> <arg line=""/> <classpath> <pathelement location="bin" /> <fileset dir="lib"> <include name="**/*.jar"/> </fileset> </classpath> </java> And when this runs I see the "Thread timed out and never died" statement, and I also see the main program finish execution, but then Ant just hangs. Presumably it is waiting for the child threads to finish, but they never will. How can I have Ant be done once it is done executing main() and just kill or ignore dead threads?

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• Is there a concurrent container library for C++

  - by Lirik

  I'm looking for implementations of lock-free containers: Blocking Queue Blocking Stack Hash Map etc... Are there any good libraries out there? I would like to refrain from writing these data structures... I would much rather use something that has been tested by the community.

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• Swing modal dialog refuses to close - sometimes!

  - by Zarkonnen

  // This is supposed to show a modal dialog and then hide it again. In practice, // this works about 75% of the time, and the other 25% of the time, the dialog // stays visible. // This is on Ubuntu 10.10, running: // OpenJDK Runtime Environment (IcedTea6 1.9) (6b20-1.9-0ubuntu1) // This always prints // setVisible(true) about to happen // setVisible(false) about to happen // setVisible(false) has just happened // even when the dialog stays visible. package modalproblemdemo; import java.awt.Frame; import javax.swing.JDialog; import javax.swing.SwingUtilities; public class Main { public static void main(String[] args) { final Dialogs d = new Dialogs(); new Thread() { @Override public void run() { d.show(); d.hide(); } }.start(); } static class Dialogs { final JDialog dialog; public Dialogs() { dialog = new JDialog((Frame) null, "Hello World", /*modal*/ true); dialog.setSize(400, 200); } public void show() { SwingUtilities.invokeLater(new Runnable() { public void run() { dialog.setLocationRelativeTo(null); System.out.println("setVisible(true) about to happen"); dialog.setVisible(true); }}); } public void hide() { SwingUtilities.invokeLater(new Runnable() { public void run() { System.out.println("setVisible(false) about to happen"); dialog.setVisible(false); System.out.println("setVisible(false) has just happened"); }}); } } }

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• c++11 atomic ordering: extended total order memory_order_seq_cst for locks

  - by itaj

  There's this note in c++11 29.3-p3: [ Note: Although it is not explicitly required that S include locks, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering. - end note ] What does it mean by "always"? I can understand that any certain implementation can be designed to support such an extended S. But in some general implementation that wasn't designed for it, I don't see that S can be extended so. I had sent this question to comp.std.c++ but got no answers there. http://groups.google.com/group/comp.std.c++/browse_frm/thread/5242fa70d0594d1b#

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• Why does System.Threading.Timer callback successfully update UI?

  - by Geo P

  I have several System.Threading.Timers on my form application with callbacks that update the UI...successfully - i.e. without throwing errors. I had built these earlier, before I knew that UI should not be updated on any thread other than the UI thread. Now I am confused as to why it does not throw cross-thread exceptions when I am updating UI on these separate threading.timer threads? I will be changing these callbacks so that the UI updates are invoked on UI thread, but I am curious as to why this works. Edit: My application is a WinForms Application.

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• Processes Allocation in .Net

  - by mayap

  I'm writing some program which should perform calculations concurrently according to inputs which reach the system all the time. I'm considering 2 approaches to allocate "calculation" processes: Allocating processes in the system initialization, insert the ids to Processes table, and each time I want to perform calculation, I will check in the table which process is free. The questions: can I be sure that those processes are only for my use and that the operating system doesn't use them? Not allocating processes in advance. Each time when calculation should be done ask the operating system for free process. I need to know the following inputs from a "calculation" process: When calculation is finished and also if it succeeded or failed If a processes has failed I need to assign the calculation to another process Thanks in advance. Any help would be appreciated.

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• C#: Populating a UI using separate threads.

  - by Andrew

  I'm trying to make some sense out of an application Ive been handed in order to track down the source of an error. Theres a bit of code (simplified here) which creates four threads which in turn populate list views on the main form. Each method gets data from the database and retrieves graphics from a resource dll in order to directly populate an imagelist and listview. From what Ive read on here (link) updating UI elements from any thread other than the UI thread should not be done, and yet this appears to work? Thread t0 = new Thread(new ThreadStart(PopulateListView1)); t0.IsBackground = true; t0.Start(); Thread t1 = new Thread(new ThreadStart(PopulateListView2)); t1.Start(); Thread t2 = new Thread(new ThreadStart(PopulateListView3)); t2.Start(); Thread t3 = new Thread(new ThreadStart(PopulateListView4)); t3.Start(); The error itself is a System.InvalidOperationException "Image cannot be added to the ImageList." which has me wondering if the above code is linked in some way. Iis this method of populating the UI recommended and if not what are the possible complications resulting from it?

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• What would happen to GC if I run process with priority = RealTime?

  - by Bobb

  I have a C# app which runs with priority RealTime. It was all fine until I made few hectic changes in past 2 days. Now it runs out of memory in few hours. I am trying to find whether it is a memory leak I created of this is because I consume lot more objects than before and GC simply cant collect them because it runs with same priority. My question is - what could happen to GC when it tries to collect objects in application with RealTime priority (there is also at least one thread running with Highest thread priority)? (P.S. by realtime priority I mean Process.GetCurrentProcess().PriorityClass = ProcessPriorityClass.RealTime) Sorry forgot to tell. GC is in Server mode

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• Should I make my MutexLock volatile?

  - by sje397

  I have some code in a function that goes something like this: void foo() { { // scope the locker MutexLocker locker(&mutex); // do some stuff.. } bar(); } The function call bar() also locks the mutex. I am having an issue whereby the program crashes (for someone else, who has not as yet provided a stack trace or more details) unless the mutex lock inside bar is disabled. Is it possible that some optimization is messing around with the way I have scoped the locker instance, and if so, would making it volatile fix it? Is that a bad idea? Thanks.

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• A generic C++ library that provides QtConcurrent functionality?

  - by Lucas

  QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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