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  • Cross Thread Exception in PropertyChangedEvent in WPF

    - by Ashish Ashu
    I have a ListView that is binded to my custom collection. At run time , I am updating the certain properties of my entity in my custom collection in my ViewModel. At the same time , I am also doing the custom sorting in the listview. The custom sorting is applicable when I click on the any column header of the listview. For example, I am updating the current datetime on my entity on every 5 seconds and simulaneously , I am applying custom sorting based on DateTime. (The Listview is third party control). Hence I am doing two operations on my custom collection at the same time. Should I pass the dispatcher of my control in the view model and call any methods ( which updates any entity in my custom collection ) through UI dispatcher ?

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  • How to deal with OpenMP thread pool contention

    - by dpe82
    I'm working on an application that uses both coarse and fine grained multi-threading. That is, we manage scheduling of large work units on a pool of threads manually, and then within those work units certain functions utilize OpenMP for finer grain multithreading. We have realized gains by selectively using OpenMP in our costliest loops, but are concerned about creating contention for the OpenMP worker pool as we add OpenMP blocks to cheaper loops. Is there a way to signal to OpenMP that a block of code should use the pool if it is available, and if not it should process the loop serially?

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  • Safe to update separate regions of a BufferedImage in separate threads?

    - by finnw
    I have a collection of BufferedImage instances, one main image and some subimages created by calling getSubImage on the main image. The subimages do not overlap. I am also making modifications to the subimage and I want to split this into multiple threads, one per subimage. From my understanding of how BufferedImage, Raster and DataBuffer work, this should be safe because: Each instance of BufferedImage (and its respective WritableRaster) is accessed from only one thread. The shared ColorModel is immutable The DataBuffer has no fields that can be modified (the only thing that can change is elements of the backing array.) Modifying disjoint segments of an array in separate threads is safe. However I cannot find anything in the documentation that says that it is definitely safe to do this. Can I assume it is safe? I know that it is possible to work on copies of the child Rasters but I would prefer to avoid this because of memory constraints. Otherwise, is it possible to make the operation thread-safe without copying regions of the parent image?

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  • Java process inputstream in thread

    - by Norbiprog
    Hi! I develop an Eclipse plugin and I have a problem My code is the following one: String run_pelda = "cmd.exe /C pelda.exe"; Runtime pelda_rt = Runtime.getRuntime(); Process pelda_proc = javacheckgen_rt.exec(run_pelda); And after I would like to read the inputstream: InputStream toolstr = tool_proc.getInputStream(); InputStreamReader r = new InputStreamReader(toolstr); BufferedReader in = new BufferedReader(r); But my new Eclipse instsnce doesn't work. I think I should do it in java threads, but unfortunatelly I don't know to use it correctly. Please give me some ideas!

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  • Ultimate Get/Post with Android Thread for Dummies

    - by Jayomat
    Hi, I'm writing an app to check for the bus timetable's. Therefor I need to post some data to a html page, submit it, and parse the resulting page with htmlparser. Though it may be asked a lot, can some one help me identify if 1) this page does support post/get (I think it does) 2) which fields I need to use? 3) How to make the actual request? this is my code so far: String url = "http://busspur02.aseag.de/bs.exe?Cmd=RV&Karten=true&DatumT=30&DatumM=4&DatumJ=2010&ZeitH=&ZeitM=&Suchen=%28S%29uchen&GT0=&HT0=&GT1=&HT1="; String charset = "CP1252"; System.out.println("startFrom: "+start_from); System.out.println("goTo: "+destination); //String tag.v List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("HTO", start_from)); params.add(new BasicNameValuePair("HT1", destination)); params.add(new BasicNameValuePair("GTO", "Aachen")); params.add(new BasicNameValuePair("GT1", "Aachen")); params.add(new BasicNameValuePair("DatumT", day)); params.add(new BasicNameValuePair("DatumM", month)); params.add(new BasicNameValuePair("DatumJ", year)); params.add(new BasicNameValuePair("ZeitH", hour)); params.add(new BasicNameValuePair("ZeitM", min)); UrlEncodedFormEntity query = new UrlEncodedFormEntity(params, charset); HttpPost post = new HttpPost(url); post.setEntity(query); InputStream response = new DefaultHttpClient().execute(post).getEntity().getContent(); // Now do your thing with the facebook response. String source = readText(response,"CP1252"); Log.d(TAG_AVV,response.toString()); System.out.println("STREAM "+source); One person also gave me a hint to use firebug to read what's going on at the page, but I don't really understand what to look for, or more precisely, how to use the provided information. I also find it confusing, for example, that when I enter the data by hand, the url says, for example, "....HTO=Kaiserplatz&...", but in Firebug, the same Kaiserplatz is connected to a different field, in this case: \<\td class="Start3" Kaiserplatz <\/td (I inserted \ to make it visible) The last line in my code prints the html page, but without having send a request.. it's printed as if there was no input at all... My app is almost done, I hope someone can help me out to finish it! thanks in advance

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  • Python thread pool similar to the multiprocessing Pool?

    - by Martin
    Is there a Pool class for worker threads, similar to the multiprocessing module's Pool class? I like for example the easy way to parallelize a map function def long_running_func(p): c_func_no_gil(p) p = multiprocessing.Pool(4) xs = p.map(long_running_func, range(100)) however I would like to do it without the overhead of creating new processes. I know about the GIL. However, in my usecase, the function will be an IO-bound C function for which the python wrapper will release the GIL before the actual function call. Do I have to write my own threading pool?

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  • Using ThreadPool.QueueUserWorkItem - thread unexpectedly exits

    - by alex
    I have the following method: public void PutFile(string ID, Stream content) { try { ThreadPool.QueueUserWorkItem(o => putFileWorker(ID, content)); } catch (Exception ex) { OnPutFileError(this, new ExceptionEventArgs { Exception = ex }); } } The putFileWorker method looks like this: private void putFileWorker(string ID, Stream content) { //Get bucket name: var bucketName = getBucketName(ID) .ToLower(); //get file key var fileKey = getFileKey(ID); try { //if the bucket doesn't exist, create it if (!Amazon.S3.Util.AmazonS3Util.DoesS3BucketExist(bucketName, s3client)) s3client.PutBucket(new PutBucketRequest { BucketName = bucketName, BucketRegion = S3Region.EU }); PutObjectRequest request = new PutObjectRequest(); request.WithBucketName(bucketName) .WithKey(fileKey) .WithInputStream(content); S3Response response = s3client.PutObject(request); var xx = response.Headers; OnPutFileCompleted(this, new ValueEventArgs { Value = ID }); } catch (Exception e) { OnPutFileError(this, new ExceptionEventArgs { Exception = e }); } } I've created a little console app to test this. I wire up event handlers for the OnPutFileError and OnPutFileCompleted events. If I call my PutFile method, and step into this, it gets to the "//if the bucket doesn't exist, create it" line, then exits. No exception, no errors, nothing. It doesn't complete (i've set breakpoints on my event handlers too) - it just exits. If I run the same method without the ThreadPool.QueueUserWorkItem then it runs fine... Am I missing something?

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  • Stack Trace of cross-thread exceptions with Invoke

    - by the_lotus
    When an exception happens after calling Invoke, .NET shows the stack trace as if the error happens while calling Invoke. Example below: .NET will say the error happen in UpdateStuff instead of UpdateStuff - BadFunction Is there a way to catch the "real" exception and show the correct stack trace? Private Sub UpdateStuff() If (Me.InvokeRequired) Then Me.Invoke(New UpdateStuffDelegate(AddressOf UpdateStuff)) Return End If Badfunction() End Sub Private Sub BadFunction() Dim o As Object o.ToString() End Sub

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  • Canceling BackgroundWorker within the Thread

    - by Mike Wills
    I have a longer running multi-step process using BackgroundWorker and C#. I need to be sure that each step is completed successfully before moving on to the next step. I have seen many references to letting the BackgroundWorker catch errors and canceling from clicking on a Cancel button, but I want to check for an error myself and then gracefully end the process. Do I treat it just like someone clicked the cancel button, or is there another way?

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  • Transactional isolation level needed for safely incrementing ids

    - by Knut Arne Vedaa
    I'm writing a small piece of software that is to insert records into a database used by a commercial application. The unique primary keys (ids) in the relevant table(s) are sequential, but does not seem to be set to "auto increment". Thus, I assume, I will have to find the largest id, increment it and use that value for the record I'm inserting. In pseudo-code for brevity: id = select max(id) from some_table id++ insert into some_table values(id, othervalues...) Now, if another thread started the same transaction before the first one finished its insert, you would get two identical ids and a failure when trying to insert the last one. You could check for that failure and retry, but a simpler solution might be setting an isolation level on the transaction. For this, would I need SERIALIZABLE or a lower level? Additionally, is this, generally, a sound way of solving the problem? Are the any other ways of doing it?

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  • C# Threading vs single thread

    - by user177883
    Is it always guaranteed that a multi-threaded application would run faster than a single threaded application? I have two threads that populates data from a data source but different entities (eg: database, from two different tables), seems like single threaded version of the application is running faster than the version with two threads. Why would the reason be? when i look at the performance monitor, both cpu s are very spikey ? is this due to context switching? what are the best practices to jack the CPU and fully utilize it? I hope this is not ambiguous.

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  • nptl SIGCONT and thread scheduling

    - by piotr
    Hello, I'm trying to port a code that relies on SIGCONT to stop certain threads of an application. With current linux nptl implementation seems one can't rely on that in 2.6.x kernels. I'm trying to devise a method to stop other threads. Currently I can only think on mutexes and condition variables. Any hints is appreciated.

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  • Do we affect multiple users in ASP.NET when we set the Thread CurrentCulture/CurentUICulture?

    - by Nikolay
    When we set the CurrentCulture and/or CurrentUICulture we do this on the current thread like this: Thread.CurrentThread.CurrentCulture = new CultureInfo("en-GB"); Thread.CurrentThread.CurrentUICulture = new CultureInfo("en-GB"); Doest this mean we could affect the culture settings of multiple users of our web application as their requests may reuse the threads from pool? I am working on an ASP.NET MVC application where each user may have own culture setting specified in his/her account data. When the user logs in, the culture setting is retrieved from the database and has to be set as current culture. My worry is that setting the current culture on the current thread may affect another user request reusing this thread. I am even more concerned reading this: ASP.NET not only uses a thread pool, but may switch threads during request processing.

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  • Passing data structures to different threads

    - by Robb
    I have an application that will be spawning multiple threads. However, I feel there might be an issue with threads accessing data that they shouldn't be. I'm relatively new to threading so bare with me. Here is the structure of the threaded application (sorry for the crudeness): MainThread / \ / \ / \ Thread A Thread B / \ / \ / \ / \ / \ / \ Thread A_1 Thread A_2 Thread B_1 Thread B_2 Under each lettered thread (which could be many), there will only be two threads and they are fired of sequentially. The issue i'm having is I'm not entirely sure how to pass in a datastructure into these threads. So, the datastructure is created in MainThread, will be modified in the lettered thread (Thread A, etc) specific to that thread and then a member variable from that datastructure is sent to Letter_Numbered threads. Currently, the lettered thread class has a member variable and when the class is constructed, the datastructure from mainthread is passed in by reference, invoking the copy constructor so the lettered thread has it's own copy to play with. The lettered_numbered thread simply takes in a string variable from the data structure within the lettered thread. My question is, is this accceptable? Is there a much better way to ensure each lettered thread gets its own data structure to play with? Sorry for the somewhat poor explanation, please leave comments and i'll try to clarify.

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  • .Net Entity objectcontext thread error

    - by Chris Klepeis
    I have an n-layered asp.net application which returns an object from my DAL to the BAL like so: public IEnumerable<SourceKey> Get(SourceKey sk) { var query = from SourceKey in _dataContext.SourceKeys select SourceKey; if (sk.sourceKey1 != null) { query = from SourceKey in query where SourceKey.sourceKey1 == sk.sourceKey1 select SourceKey; } return query.AsEnumerable(); } This result passes through my business layer and hits the UI layer to display to the end users. I do not lazy load to prevent query execution in other layers of my application. I created another function in my DAL to delete objects: public void Delete(SourceKey sk) { try { _dataContext.DeleteObject(sk); _dataContext.SaveChanges(); } catch (Exception ex) { Debug.WriteLine(ex.Message + " " + ex.StackTrace + " " + ex.InnerException); } } When I try to call "Delete" after calling the "Get" function, I receive this error: New transaction is not allowed because there are other threads running in the session This is an ASP.Net app. My DAL contains an entity data model. The class in which I have the above functions share the same _dataContext, which is instantiated in my constructor. My guess is that the reader is still open from the "Get" function and was not closed. How can I close it?

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  • Thread Proc for an instancable class?

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

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  • Google groups not finding discussion thread but regular google search does?

    - by Mathias Lin
    I'm having a problem with google groups and finding my own discussion threads. I go to the google group (in my case Android developer group) web view and try to search for my thread by entering the extact title of my thread. But it doesn't appear in the search results. On the other hand, when I search for the same title in the regular google web search, I get the thread right on top of the result list. I thought it might take a while until the groups index all new threads, but still after a few days, it still wouldn't show up. Sample: My thread is here: http://groups.google.com/group/android-developers/browse_thread/thread/0ab41d5056a25ce7 Doing a search for it in Google groups (will give one result, but not mine): http://groups.google.com/group/android-developers/search?group=android-developers&q=Strange+behaviour+with+mediaplayer+and+seekTo&qt_g=Search+this+group Search in Google web search (shows my thread as first result): http://www.google.de/search?sourceid=chrome&ie=UTF-8&q=Strange+behaviour+with+mediaplayer+and+seekTo

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  • C# Thread Queue Synchronize

    - by ikurtz
    Greetings, I am trying to play some audio files without holding up the GUI. Below is a sample of the code: if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(CoordinateProc), fireResult)) { } else { MessageBox.Show("false"); } } if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(FireProc), fireResult)) { } else { MessageBox.Show("false"); } } if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(HitProc), fireResult)) { } else { MessageBox.Show("false"); } } The situation is the samples are not being played in order. some play before the other and I need to fix this so the samples are played one after another in order. How do I implement this please? Thank you.

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  • Jasper error: Caused by SQLServerException: Transaction (Process ID 58) was deadlocked on thread | c

    - by Saky
    I got the above error in my jasper report mail. The query that is used in the report is quite complicated (for me). Reading different posts I conclude that to solve this the I have to change the query to SET TRANSACTION ISOLATION LEVEL REPEATABLE READ GO BEGIN TRANSACTION ... my query ... COMMIT TRANSACTION ? I wonder if this is the correct way to solve the error and that if it has any side effects? Has it happened to anyone in the Jasper reports? Does anyone know if there is a better solution exist to the problem? (Although that I have not yet tested the above solution, if anyone can give any insight on this will be helpful.)

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  • How to allow one thread to mutate an array property while another thread iterates on a copy of the a

    - by Steve918
    I would like to implement an observer pattern in Objective-C where the observer implements an interface similar to SKPaymentTransactionObserver and the observable class just extends my base observable. My observable class looks something like what is below. Notice I'm making copies of the observers before enumeration to avoid throwing an exception . I've tried adding an NSLock around add observers and notify observers, but I run into a deadlock. What would be the proper way to handle concurrency when observers are being added as notifications are being sent? @implementation Observable -(void)notifyObservers:(SEL)selector { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector]; } } [observer_copy release]; } } -(void)notifyObservers:(SEL)selector withObject:(id)arg1 withObject:(id)arg2 { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector withObject: arg1 withObject: arg2]; } } [observer_copy release]; } } -(void)addObserver:(id)observer { @synchronized(self) { [observers addObject: observer]; } } -(void)removeObserver:(id)observer { @synchronized(self) { [observers removeObject: observer]; } }

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  • using volatile keyword

    - by sap
    As i understand, if we declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. But in the following program both volatile and non-volatile variables are displaying same value. The volatile variable is not updated for the second thread. Can anybody plz explain this why testValue is not changed. class ExampleThread extends Thread { private int testValue1; private volatile int testValue; public ExampleThread(String str){ super(str); } public void run() { if (getName().equals("Thread 1 ")) { testValue = 10; testValue1= 10; System.out.println( "Thread 1 testValue1 : " + testValue1); System.out.println( "Thread 1 testValue : " + testValue); } if (getName().equals("Thread 2 ")) { System.out.println( "Thread 2 testValue1 : " + testValue1); System.out.println( "Thread 2 testValue : " + testValue); } } } public class VolatileExample { public static void main(String args[]) { new ExampleThread("Thread 1 ").start(); new ExampleThread("Thread 2 ").start(); } } output: Thread 1 testValue1 : 10 Thread 1 testValue : 10 Thread 2 testValue1 : 0 Thread 2 testValue : 0

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