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• System.WIndows.Application static members are thread safe?

  - by Lirik

  The Application static members are supposed to be thread safe: The public static (Shared in Visual Basic) members of this type are thread safe. In addition, the FindResource and TryFindResource methods and the Properties and Resources properties are thread safe.1 How much can we trust that statement in a multithreaded environment when calling static member methods of System.Windows.Application? Update: It's all in reference to this question: http://stackoverflow.com/questions/2463822/threading-errors-with-application-loadcomponent-key-already-exists/2463866#2463866 I never thought I'd see a real bug in the library, but this must be the day for me... that question seems to show a genuine bug. Usually it's "user error," but this doesn't seem to be the case.

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• Allowing threads from python after calling a blocking i/o code in a python extension generated using

  - by SS

  I have written a python extension wrapping an existing C++ library live555 (wrapping RTSP client interface to be specific) in SWIG. The extension works when it is operated in a single thread, but as soon as I call the event loop function of the library, python interpreter never gets the control back. So if I create a scheduled task using threading.Timer right before calling the event loop, that task never gets executed once event loop starts. To fix this issue, I added Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS macros manually in the SWIG auto generated wrapper cxx file around every doEventLoop() function call. But now, I want to do the same (i.e. allow threads) when SWIG generates the code itself and not to change any code manually. Has anyone done something similar in SWIG? P.S. - I would also consider switching to any other framework (like SIP) to get this working. I selected SWIG over any other technology is because writing SWIG interface was really very easy and I just had to include the existing header files.

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• Thread safety of Matlab engine API

  - by Jeremy

  I have discovered through trial and error that the MATLAB engine function is not completely thread safe. Does anyone know the rules? Discovered through trial and error: On Windows, the connection to MATLAB is via COM, so the COM Apartment threading rules apply. All calls must occur in the same thread, but multiple connections can occur in multiple threads as long as each connection is isolated. From the answers below, it seems that this is not the case on UNIX, where calls can be made from multiple threads as long as the calls are made serially.

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• How to stop ReSharper from showing error on a lambda expression where Action is expected?

  - by carlmon

  In Silverlight, System.Windows.Threading's Dispatcher.BeginInvoke() takes an Action<T> or a delegate to invoke. .NET allows me to pass just the lambda expression. but ReSharper sees it as an error, saying "Cannot resolve method 'BeginInvoke(lambda expression)'": Dispatcher.BeginInvoke(() => { DoSomething(); }) The error goes away if I explicitly create the Action around the expression like this: Dispatcher.BeginInvoke(new Action<object>(o => { DoSomething(); })); I prefer the least amount of code in this case for the best readability. Is there a way to disable this specific ReSharper error notification? I tried some of the options, but could not find it. Thanks, Carl

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• Multithreading in Lua

  - by RCIX

  I was having a discussion with my friend the other day. I was saying how that, in pure Lua, you couldn't build a preemptive multitasking system. He claims you can, because of the following reason: Both C and Lua have no inbuilt threading libraries [OP's note: well, Lua technically does, but AFAIK it's not useful for our purposes]. Windows, which is written in mostly C(++) has pre-emptive multitasking, which they built from scratch. Therefore, you should be able to do the same in Lua. The big problem i see with that is that the main way preemptive multitasking works (to my knowledge) is that it generates regular interrupts which the manager uses to get control and determine what code it should be working on next. I also don't think Lua has any facility that can do that. My question is: is it possible to write a pure-Lua library that allows people to have pre-emptive multitasking?

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• Named semaphores in Python?

  - by Boaz

  Hi, I have a script in python which uses a resource which can not be used by more than a certain amount of concurrent scripts running. Classically, this would be solved by a named semaphores but I can not find those in the documentation of the multiprocessing module or threading . Am I missing something or are named semaphores not implemented / exposed by Python? and more importantly, if the answer is no, what is the best way to emulate one? Thanks, Boaz PS. For reasons which are not so relevant to this question, I can not aggregate the task to a continuously running process/daemon or work with spawned processed - both of which, it seems, would have worked with the python API.

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

  - by rwmnau

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

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• C# how to wait for a webpage to finish loading before continuing

  - by MD6380

  I'm trying to create a program to clone multiple bugs at a time through the web interface of our defect tracking system. How can I wait before a page is completely loaded before I continue? //This is pseudo code, but this should give you an idea of what I'm trying to do. The //actual code uses multi-threading and all that good stuff :). foreach (string bug in bugs) { webBrowser.Navigate(new Uri(url)); webBrowser.Document.GetElementById("product").SetAttribute("value", product); webBrowser.Document.GetElementById("version").SetAttribute("value", version); webBrowser.Document.GetElementById("commit").InvokeMember("click"); //Need code to wait for page to load before continuing. }

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• Timer in windows service

  - by Markus

  Hi. I have an issue with System.Threading.Timer. I am scheduling some actions using a time in a windows service. The timer starts executing the callback after a specified dueTime period. The windows service starts up after reboot automatically. However, I have observed a strange thing after a system reboot- the callback method starts executing itself 3 or 4 minutes before the specified period. What might be the reason for such behavior? Here is the sample code: TimeSpan timeToWait = this.StartTime - DateTime.Now; Int64 msToSleep = (Int64)Math.Round(timeToWait.TotalMilliseconds); _timer = new Timer(callback_method, null, msToSleep, MinutesScheduledInterval * 60000); where _timer is a member variable, StartTime - the time when the timer should first fire.

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• Which thread invokes SensorEventListener.onSensorChanged

  - by Christoph Heindl

  From my records it seems that SensorEventListener.onSensorChanged callback is called by the same thread that registered the callback. I.e there must be some message-queue synchronization going on in the background which allows the activitys UI-Thread to handle the callbacks. That leads to my question: Is there a need to synchronize SensorEventListener.onSensorChanged with the activitys UI-thread, assuming that the activitys UI-thread registered the SensorEventListener? I cannot find any documentation references, but can see various examples calling invalidate() unsychronized or synchronize the entire callback. I used something along the lines of Log.i(TAG, "" + Thread.currentThread().getId()); to retrieve threading information. I'm running android 2.1 update1. Best regards, Christoph

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• Using multithreading for loop

  - by annelie

  Hello, I'm new to threading and want to do something similar to this question: http://stackoverflow.com/questions/100291/speed-up-loop-using-multithreading-in-c-question However, I'm not sure if that solution is the best one for me as I want them to keep running and never finish. (I'm also using .net 3.5 rather than 2.0 as for that question.) I want to do something like this: foreach (Agent agent in AgentList) { // I want to start a new thread for each of these agent.DoProcessLoop(); } --- public void DoProcessLoop() { while (true) { // do the processing // this is things like check folder for new files, update database // if new files found } } Would a ThreadPool be the best solution or is there something that suits this better? Thanks, Annelie

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• Someone explain to me the meanings behind the naming conventions used in .net?

  - by IbrarMumtaz

  I need someone to explain the following names; Asynchronous Delegates. Asynchronous methods. Asynchronous events. I'm currently going over this for my 70-536 exam and I am covering all my bases so far. The threading chapter and online resources have been good to me on my second read through. Still though, the names used above mean absolutely nothing to me? I would really appreciate the meaning behind the word 'Asynchronous' and its relevance to Delegates, methods and events. Feel free to go into as much detail as you like. Thanks, Ibrar

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• Async Socket Listener on separate thread - VB.net

  - by TheHockeyGeek

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

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• Unhandled exceptions in BackgroundWorker

  - by edg

  My WinForms app uses a number of BackgroundWorker objects to retrieve information from a database. I'm using BackgroundWorker because it allows the UI to remain unblocked during long-running database queries and it simplifies the threading model for me. I'm getting occasional DatabaseExceptions in some of these background threads, and I have witnessed at least one of these exceptions in a worker thread while debugging. I'm fairly confident these exceptions are timeouts which I suppose its reasonable to expect from time to time. My question is about what happens when an unhandled exception occurs in one of these background worker threads. I don't think I can catch an exception in another thread, but can I expect my WorkerCompleted method to be executed? Is there any property or method of the BackgroundWorker I can interrogate for exceptions?

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• How to re-use a thread in Java ?

  - by David

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

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• Preprocessor macros: how to insert arguments?

  - by mhambra

  Hi all, the code has a number of following sections: int filter; #ifdef INPUTFILTER_FOO LOG4CXX_DEBUG(log, "FOO filter used"); filter = F_FOO; #endif They are used multiple times in the code (used to provide I/O, threading support etc for all testing configurations), Circa they are essential for debugging but make the code look harsh, want to replace them with macros, one for each category_type namespace. So, want to expand the following: MACROSTUFFBAZ(log2, stuff, "BAZ") <- the text part is unique for each class, so it needs to be included in macro too. to: #ifdef INPUTSTUFF_BAZ LOG4CXX_DEBUG(log2, "BAZ stuff used"); stuff = S_BAZ; #endif To define macros, plan to use this: debug.hpp: #ifdef INPUTSTUFF_BAZ #define MACROSTUFFBAZ ... #else #define MACROSTUFFBAZ .. no code! #endif #endif (at least this will give a clear overview of the things currently undergoing probation, without seeing them around the code)

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• WPF DataGrid adding extra "ghost" row

  - by hs2d

  Hei, In my application i'm using DataGrid to show some data. To get everything working with threading i'm using AsyncObservableCollection as DataContext of DataGrid. When my application starts it looks for files in some folders and updates AsyncObservableCollection. Now here's where things go bad, when i start the application for some reason i get 2 rows with same data in DataGrid even if there is one item in collection. If i add a delay(Thread.Sleep() 50ms minimum) before executing loading files method then DataGrid show everything correctly (no extra row). Have anybody encountered something similar or is there something else i should try? Thanks in advance!

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• crashing out in a while loop python

  - by Edward

  How to solve this error? i want to pass the values from get_robotxya() and get_ballxya() and use it in a loop but it seems that it will crash after awhile how do i fix this? i want to get the values whithout it crashing out of the while loop import socket import os,sys import time from threading import Thread HOST = '59.191.193.59' PORT = 5555 COORDINATES = [] def connect(): globals()['client_socket'] = socket.socket(socket.AF_INET, socket.SOCK_STREAM) client_socket.connect((HOST,PORT)) def update_coordinates(): connect() screen_width = 0 screen_height = 0 while True: try: client_socket.send("loc\n") data = client_socket.recv(8192) except: connect(); continue; globals()['COORDINATES'] = data.split() if(not(COORDINATES[-1] == "eom" and COORDINATES[0] == "start")): continue if (screen_width != int(COORDINATES[2])): screen_width = int(COORDINATES[2]) screen_height = int(COORDINATES[3]) return def get_ballxy(): update_coordinates() ballx = int(COORDINATES[8]) bally = int(COORDINATES[9]) return ballx,bally def get_robotxya(): update_coordinates() robotx = int(COORDINATES[12]) roboty = int(COORDINATES[13]) angle = int(COORDINATES[14]) return robotx,roboty,angle def print_ballxy(bx,by): print bx print by def print_robotxya(rx,ry,a): print rx print ry print a def activate(): bx,by = get_ballxy() rx,ry,a = get_robotxya() print_ballxy(bx,by) print_robotxya(rx,ry,a) Thread(target=update_coordinates).start() while True: activate() this is the error i get:

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• Is it possible to have an out-of-process COM server where a separate O/S process is used for each ob

  - by Tom Williams

  I have a legacy C++ "solution engine" that I have already wrapped as an in-process COM object for use by client applications that only require a single "solution engine". However I now have a client application that requires multiple "solution engines". Unfortunately the underlying legacy code has enough global data, singletons and threading horrors that given available resources it isn't possible to have multiple instances of it in-process simultaneously. What I am hoping is that some kind soul can tell me of some COM magic where with the flip of a couple of registry settings it is possible to have a separate out-of-process COM server (separate operating system process) for each instance of the COM object requested. Am I in luck?

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• Looking for an explanation of the 'Asynchronous' word in .Net?

  - by IbrarMumtaz

  I need someone to explain the following names; Asynchronous Delegates. Asynchronous methods. Asynchronous events. I'm currently going over this for my 70-536 exam and I am covering all my bases so far. The threading chapter and online resources have been good to me on my second read through. Still though, the names used above mean absolutely nothing to me? I would really appreciate the meaning behind the word 'Asynchronous' and its relevance to Delegates, methods and events. Feel free to go into as much detail as you like. Thanks, Ibrar

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• C# timer getting fired before their interval time

  - by Swati Ghaisas

  Hi, We're getting following problem while using system.threading.timer ( .net framework 2.0 ) from a Windows service. There are around 12 different timer objects.. Each timer has due time and interval. This is set correctly. It is observed that after 3 to 4 hours, the timers start signalling before their interval elapses. For example if the timer is supposed to signal at 4:59:59, it gets signalled at 4:59:52, 7 seconds earlier. Can someone tell me what is the cause for this behavior and what is the solution for that ? Thanks, Swati

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• C# myths about best practices?

  - by TheMachineCharmer

  My colleague keeps telling me of the things listed in comments. I am confused. Can somebody please demystify these things for me? class Bar { private int _a; public int A { get { return _a; } set { _a = value; } } private Foo _objfoo; public Foo OFoo { get { return _objfoo; } set { _objfoo = value; } } public Bar(int a, Foo foo) { // this is a bad idea A = a; OFoo = foo; } // MYTHS private void Method() { this.A //1 - this._a //2 - use this when inside the class e.g. if(this._a == 2) A //3 - use this outside the class e.g. barObj.A _a //4 - // Not using this.xxx creates threading issues. } } class Foo { // implementation }

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• Can you dynamically resize a java.util.concurrent.ThreadPoolExecutor while it still has tasks waitin

  - by Edward Shtern

  I'm working with a java.util.concurrent.ThreadPoolExecutor to process a number of items in parallel. Although the threading itself works fine, at times we've run into other resource constraints due to actions happening in the threads, which made us want to dial down the number of Threads in the pool. I'd like to know if there's a way to dial down the number of the threads while the threads area actually working. I know that you can call setMaximumPoolSize() and/or setCorePoolSize(), but these only resize the pool once threads become idle, but they don't become idle until there are no tasks waiting in the queue.

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• Is VS2010 Premium Worth the Price?

  - by WindyCityEagle

  I know this is somewhat subjective, but I can't find an honest answer anywhere. Everything concerning VS2010 are Microsoft marketing materials. Our small group is going to upgrade to VS2010(mostly for F# and the new threading features), but we can't decide between the Professional and Premium versions. The integrated testing features in Premium sound good, but I can' figure out if they're worth the 10x increase in cost between the two versions(Professional is ~549, Premium is ~5400). Has anyone been faced with a similar decision? What swayed you one way or the other?

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• Multithreading Errors in C#

  - by Adam

  Hi. I am trying to update a text box. I thought my threading code would fix the problem, but it does not. Can anyone help with this? new Thread((ThreadStart)delegate { txtCapacitance.Text = Math.Round(capacitance, 3).ToString(); }).Start(); Gives the following error: Cross-thread operation not valid: Control 'txtCapacitance' accessed from a thread other than the thread it was created on. Note that all this is being started by a dataReceived function which is called whenever USB data is received.

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