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  • Calculating string sizes on iPhone on a background thread

    - by jbrennan
    I've got some somewhat hefty string size calculations happening in my app (each one takes close to 500ms, and happens when the user scrolls to a new "page" in my app (like the Weather app). The delay only happens once per page, as the calculation only needs to be run once (and can even be cached for subsequent launches with the same data). Anyway, I still like to not block the UI for this type of work, as to me it screams using threads, but I know UIKit is not meant to be used from other threads. (I know NSString is not part of UIKit, but the string sizing methods are part of the UIKitAdditions...) So how should I go about doing this? What's the best way to not block the UI and do so safely?

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  • Quartz Thread Execution Parallel or Sequential?

    - by vikas
    We have a quartz based scheduler application which runs about 1000 jobs per minute which are evenly distributed across seconds of each minute i.e. about 16-17 jobs per second. Ideally, these 16-17 jobs should fire at same time, however our first statement, which simply logs the time of execution, of execute method of the job is being called very late. e.g. let us assume we have 1000 jobs scheduled per minute from 05:00 to 05:04. So, ideally the job which is scheduled at 05:03:50 should have logged the first statement of the execute method at 05:03:50, however, it is doing it at about 05:06:38. I have tracked down the time taken by the scheduled job which comes around 15-20 milliseconds. This scheduled job is fast enough because we just send a message on an ActiveMQ queue. We have specified the number of threads of quartz to be 100 and even tried with increasing it to 200 and more, but no gain. One more thing we noticed is that logs from scheduler are coming sequential after first 1 minute i.e. [Quartz_Worker_28] <Some log statement> .. .. [Quartz_Worker_29] <Some log statement> .. .. [Quartz_Worker_30] <Some log statement> .. .. So it suggesting that after some time quartz is running threads almost sequential. May be this is happening due to the time taken in notifying the job completion to persistence store (which is a separate postgres database in this case) and/or context switching. What can be the reason behind this strange behavior? EDIT: More detailed Log [06/07/12 10:08:37:192][QuartzScheduler_Worker-34][INFO] org.quartz.plugins.history.LoggingTriggerHistoryPlugin - Trigger [<trigger_name>] fired job [<job_name>] scheduled at: 06-07-2012 10:08:33.458, next scheduled at: 06-07-2012 10:34:53.000 [06/07/12 10:08:37:192][QuartzScheduler_Worker-34][INFO] <my_package>.scheduler.quartz.ScheduledLocateJob - execute begin--------- ScheduledLocateJob with key: <job_name> started at Fri Jul 06 10:08:37 EDT 2012 [06/07/12 10:08:37:192][QuartzScheduler_Worker-34][INFO] <my_package>.scheduler.quartz.ScheduledLocateJob <some log statement> [06/07/12 10:08:37:192][QuartzScheduler_Worker-34][INFO] <my_package>.scheduler.quartz.ScheduledLocateJob <some log statement> [06/07/12 10:08:37:192][QuartzScheduler_Worker-34][INFO] <my_package>.scheduler.quartz.ScheduledLocateJob <some log statement> [06/07/12 10:08:37:220][QuartzScheduler_Worker-34][INFO] <my_package>.scheduler.quartz.ScheduledLocateJob - execute end--------- ScheduledLocateJob with key: <job_name> ended at Fri Jul 06 10:08:37 EDT 2012 [06/07/12 10:08:37:220][QuartzScheduler_Worker-34][INFO] org.quartz.plugins.history.LoggingTriggerHistoryPlugin - Trigger [<trigger_name>] completed firing job [<job_name>] with resulting trigger instruction code: DO NOTHING. Next scheduled at: 06-07-2012 10:34:53.000 I am doubting on this section of the above log scheduled at: 06-07-2012 10:08:33.458, next scheduled at: 06-07-2012 10:34:53.000 because this job was scheduled for 10:04:53, but it fired at 10:08:33 and still quartz didn't consider it as misfire. Shouldn't it be a misfire?

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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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  • 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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  • 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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  • Is this code thread safe?

    - by Shawn Simon
    ''' <summary> ''' Returns true if a submission by the same IP address has not been submitted in the past n minutes. ''' </summary> Protected Function EnforceMinTimeBetweenSubmissions() As Boolean Dim minTimeBetweenRequestsMinutes As Integer = 0 Dim configuredTime = ConfigurationManager.AppSettings("MinTimeBetweenSchedulingRequestsMinutes") If String.IsNullOrEmpty(configuredTime) Then Return True If (Not Integer.TryParse(configuredTime, minTimeBetweenRequestsMinutes)) _ OrElse minTimeBetweenRequestsMinutes > 1440 _ OrElse minTimeBetweenRequestsMinutes < 0 Then Throw New ApplicationException("Invalid configuration setting for AppSetting 'MinTimeBetweenSchedulingRequestsMinutes'") End If If minTimeBetweenRequestsMinutes = 0 Then Return True End If If Cache("submitted-requests") Is Nothing Then Cache("submitted-requests") = New Dictionary(Of String, Date) End If ' Remove old requests. Dim submittedRequests As Dictionary(Of String, Date) = CType(Cache("submitted-requests"), Dictionary(Of String, Date)) Dim itemsToRemove = submittedRequests.Where(Function(s) s.Value < Now).Select(Function(s) s.Key).ToList For Each key As String In itemsToRemove submittedRequests.Remove(key) Next If submittedRequests.ContainsKey(Request.UserHostAddress) Then ' User has submitted a request in the past n minutes. Return False Else submittedRequests.Add(Request.UserHostAddress, Now.AddMinutes(minTimeBetweenRequestsMinutes)) End If Return True End Function

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • .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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  • 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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  • 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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  • Multi-thread conversation in django (like Reddit)

    - by dotty
    Hay, i have an app which essentially a conversation system (much like reddits) Where a post can have multiple replies, and a reply and have multiplies, and a reply to a reply can have multiple replies (etc) I've made the model like this class Discussion(models.Model): message = models.TextField() replies = models.ManyToManyField('self') and the view discussions = Discussions.objects.all() and the template looks like this {% for discussion in discussions %} {{ discussion.message }} {% endfor %} How would i go about making a system where i can output all replies like this discussion reply reply reply reply reply reply Which would go down as far as it needs to to ensure all replies are listed. Thanks

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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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  • Recommendations for an in memory database vs thread safe data structures

    - by yx
    TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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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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