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  • Force redraw before long running operations

    - by Joshua
    When you have a button, and do something like: Private Function Button_OnClick Button.Enabled = False [LONG OPERATION] End Function Then the button will not be grayed, because the long operation prevents the UI thread from repainting the control. I know the right design is to start a background thread / dispatcher, but sometimes that's too much hassle for a simple operation. So how do I force the button to redraw in disabled state? I tried .UpdateLayout() on the Button, but it didn't have any effects. I also tried System.Windows.Forms.DoEvents() which normally works when using WinForms, but it also had no effect.

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  • Efficient implementation of threads in the given scenario

    - by shadeMe
    I've got a winforms application that is set up in the following manner: 2 buttons, a textbox, a collection K, function X and another function, Y. Function X parses a large database and enumerates some of its data in the global collection. Button 1 calls function X. Function Y walks through the above collection and prints out the data in the textbox. Button 2 calls function Y. I'd like to call function X through a worker thread in such a way that: The form remains responsive to user input. This comes intrinsically from the use of a separate thread. There is never more than a single instance of function X running at any point in time. K can be accessed by both functions at all times. What would be the most efficient implementation of the above environment ?

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  • java thread - run() and start() methods

    - by JavaUser
    Please explain the output of the below code: If I call th1.run() ,the output is EXTENDS RUN RUNNABLE RUN If I call th1.start() , the output is : RUNNABLE RUN EXTENDS RUN Why this inconsistency . Please explain. class ThreadExample extends Thread{ public void run(){ System.out.println("EXTENDS RUN"); } } class ThreadExampleRunnable implements Runnable { public void run(){ System.out.println("RUNNABLE RUN "); } } class ThreadExampleMain{ public static void main(String[] args){ ThreadExample th1 = new ThreadExample(); //th1.start(); th1.run(); ThreadExampleRunnable th2 = new ThreadExampleRunnable(); th2.run(); } }

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  • How can you set a time limit for a PowerShell script to run for?

    - by calrain
    I want to set a time limit on a PowerShell (v2) script so it forcibly exits after that time limit has expired. I see in PHP they have commands like set_time_limit and max_execution_time where you can limit how long the script and even a function can execute for. With my script, a do/while loop that is looking at the time isn't appropriate as I am calling an external code library that can just hang for a long time. I want to limit a block of code and only allow it to run for x seconds, after which I will terminate that code block and return a response to the user that the script timed out. I have looked at background jobs but they operate in a different thread so won't have kill rights over the parent thread. Has anyone dealt with this or have a solution? Thanks!

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  • ASP.NET Thread Safety in aspx.cs code behind file

    - by Tim Michalski
    I am thinking of adding a DataContext as a member variable to my aspx.cs code-behind class for executing LinqToSql queries. Is this thread safe? I am not sure if a new instance of this code-behind class is created for each HTTP request, or if the instance is shared amongst all request threads? My fear is that I will get 10 simultaneous concurrent http requests that will be using the same database session. public partial class MyPage : System.Web.UI.Page { private DataContext myDB = new DataContext(); protected void MyAction_Click(object sender, EventArgs e) { myDB.DoWork(); } }

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  • SslStream.ReadByte() blocks thread?

    - by alex
    I'm trying to write an Imap4 client. For that I use a SslStream to Connect to the Server. Everything's fine until I send the "Login" command. When I try to get an Answer to it, SslStream.ReadByte() block the thread. The result is that my programm crashes always. Whats happening here?? Code: if (ssl) { s = stream; } int cc = 0; MessageBox.Show("entered"); while (true) { int xs = s.ReadByte(); MessageBox.Show(xs.ToString()); if (xs > 0) { buf.Add((byte)xs); cc++; if (xs == '\n') { break; } if (cc > 10) MessageBox.Show(en.GetString(buf.ToArray())); } else { break; } } MessageBox.Show("left");

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  • How to end a thread in java?

    - by beagleguy
    hi all, I have 2 pools of threads ioThreads = (ThreadPoolExecutor)Executors.newCachedThreadPool(); cpuThreads = (ThreadPoolExecutor)Executors.newFixedThreadPool(numCpus); I have a simple web crawler that I want to create an iothread, pass it a url, it will then fetch the url and pass the contents over to a cpuThread to be processed and the ioThread will then fetch another url, etc... At some point the IO thread will not have any new pages to crawl and I want to update my database that this session is complete. How can I best tell when the threads are all done processing and the program can be ended?

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  • ThreadStateException when using QueueUserWorkItem in a Timer

    - by Tim
    Hi all, I have a ThreadStateException in my winforms application. Step to reproduce : Create simple winforms app Add a button In click event, do : timer1.Interval = 1000; timer1.Tick += timer1_Tick; timer1.Start(); void timer1_Tick(object sender, EventArgs e) { ThreadPool.QueueUserWorkItem(delegate { StringCollection paths = new StringCollection { @"c:\my.txt", @"c:\my.png" }; Clipboard.SetFileDropList(paths); }); } The exception tells me : Current thread must be set to single thread apartment (STA) mode before OLE calls can be made. Ensure that your Main function has STAThreadAttribute marked on it. But the main has already the [STAThread] attribute. How to solve it ? Thanks in advance for any help

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  • C++ Static Initializer - Is it thread safe

    - by Yan Cheng CHEOK
    Usually, when I try to initialize a static variable class Test2 { public: static vector<string> stringList; private: static bool __init; static bool init() { stringList.push_back("string1"); stringList.push_back("string2"); stringList.push_back("string3"); return true; } }; // Implement vector<string> Test2::stringList; bool Test2::__init = Test2::init(); Is the following code thread safe, during static variable initialization? Is there any better way to static initialize stringlist, instead of using a seperate static function (init)?

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  • Are static delegates thread-safe?

    - by leypascua
    Consider this code snippet: public static class ApplicationContext { private static Func<TService> Uninitialized<TService>() { throw new InvalidOperationException(); } public static Func<IAuthenticationProvider> AuthenticationProvider = Uninitialized<IAuthenticationProvider>(); public static Func<IUnitOfWorkFactory> UnitOfWorkFactory = Uninitialized<IUnitOfWorkFactory>(); } //can also be in global.asax if used in a web app. public static void Main(string[] args) { ApplicationContext.AuthenticationProvider = () => new LdapAuthenticationProvider(); ApplicationContext.UnitOfWorkFactory = () => new EFUnitOfWorkFactory(); } //somewhere in the code.. say an ASP.NET MVC controller ApplicationContext.AuthenticationProvider().SignIn(username, true); Are delegates in the static class ApplicationContext thread-safe in the sense that multiple-threads can invoke them? What potential problems will I face if I pursue this approach?

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  • SQL - get the article title with the last comment date

    - by stacker
    I have articles table, article_comments. I want to get the value: last_modified_all of article. I need this value to be the great date of this two: the last_modified field of articles table. the last comment of article_comments last_modified column. Can someone help me? the structure is very simple, and you can guess is without problem.

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  • Java - Thread safety of ArrayList constructors

    - by andy boot
    I am looking at this piece of code. This constructor delegates to the native method "System.arraycopy" Is it Thread safe? And by that I mean can it ever throw a ConcurrentModificationException? public Collection<Object> getConnections(Collection<Object> someCollection) { return new ArrayList<Object>(someCollection); } Does it make any difference if the collection being copied is ThreadSafe eg a CopyOnWriteArrayList? public Collection<Object> getConnections(CopyOnWriteArrayList<Object> someCollection) { return new ArrayList<Object>(someCollection); }

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  • How can I pass a Context object to a thread on call

    - by Pentium10
    I have this code fragment: public static class ExportDatabaseFileTask extends AsyncTask<String, Void, Boolean> { private final ProgressDialog dialog = new ProgressDialog(ctx); protected void onPreExecute(); protected Boolean doInBackground(final String... args); protected void onPostExecute(final Boolean success); } I execute this thread as new ExportDatabaseFileTask().execute(); As you see I use a ctx as Context variable in the new ProgressDialog call, how do I pass a context to the call method? to this one: new ExportDatabaseFileTask().execute();*

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  • Thread processing in EMS connection

    - by aladine
    I am setting up a client and exchange project and both are connecting to a remote server. Exchange will connect to the server by EMS connection. While client will connect by FIX. For the aim of building of black box testing, both client and exchange engine will be given some predefined testcases to send and receive to the server. I design the client engine with multithread processing to manipulate many testcases. Actually it is able to run succesfully. For exchange engine, I wonder that multi thread is applicable in the context that the exchange engine just need to publish a message when it received msg from subscribed topic on server. Flow of messages transmission: Client--SERVER--Exchange FIX EMS Exchange--SERVER--Client EMS FIX Thanks if you can help me on this issue.

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  • Does this simple cache class need thread synchronization?

    - by DayOne
    Does this simple cache class need thread synchronization ... if I remove the lock _syncLock statement will encounter any problems? I think i can remove the locks as the references should be updated correctly right? ... BUt i'm think whar happens if client code is iterating over the GetMyDataStructure method and it get replaced? Thanks! public sealed class Cache { private readonly object _syncLock = new object(); private IDictionary<int, MyDataStructure> _cache; public Cache() { Refresh(); } public void Refresh() { lock (_syncLock) { _cache = DAL.GetMyDataStructure(); } } public IDictionary<int, MyDataStructure> **GetMyDataStructure**() { lock (_syncLock) { return _cache; } } }

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  • How can CopyOnWriteArrayList be thread-safe?

    - by Shooshpanchick
    I've taken a look into OpenJDK's sources of CopyOnWriteArrayList and it seems that all write operations are protected by the same lock and read operations are not protected at all. As I understand, under JMM all accesses to a variable (both read and write) should be protected by lock or reordering effects may occur. For example, set(int, E) method contains these lines (under lock): /* 1 */ int len = elements.length; /* 2 */ Object[] newElements = Arrays.copyOf(elements, len); /* 3 */ newElements[index] = element; /* 4 */ setArray(newElements); The get(int) method, on the other hand, only does return get(getArray(), index);. In my understanding of JMM, this means that get may observe the array in an inconsistent state if statements 1-4 are reordered like 1-2(new)-4-2(copyOf)-3. Do I understand JMM incorrectly or is there any other explanations on why CopyOnWriteArrayList is thread-safe?

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  • Grid computing projects similar to NGrid (thread based)

    - by DivdeAndConquer
    Hello there, first time poster. This is a great place for reading about programming problems. I've been looking at some grid computing projects for .Net/Mono and stumbled upon NGrid. NGrid seems really appealing for grid computing because you simply pass threads to it and there is very little modification you have to make to your code. However, I see that NGrid (http://ngrid.sourceforge.net/?page=overview) is still at version 0.7 and hasn't been updated since May 2008. So, I'm wondering if there are any other grid computing projects that use a similar thread-passing architecture and if anyone has had success using NGrid.

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  • too many threads due to synch communication

    - by MasoudIzzy
    I'm using threads and xmlrpclib in python at the same time. Periodically, I create a bunch of thread to complete a service on a remote server via xmlrpclib. The problem is that, there are times that the remote server doesn't answer. This causes the thread to wait forever for a response which it never gets. Over time, number of threads in this state increases and will reach the maximum number of allowed threads on the system (I'm using fedora). I tried to use socket.setdefaulttimeout(10); but the exception that is created by that will cause the server to defunct. I used it at server side but it seems that it doesn't work :/ Any idea how can I handle this issue?

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  • Serialized task distribution: use thread or epoll?

    - by hpsmouse
    Now I'm in such a situation that there is a group of predefined tasks for multiple clients to do(any client can take any task). When a client connects to the server, server choose a task from the uncompleted tasks and send it to the client. It takes a while for the client to finish the task and send the result back to the server. Since a task should be sent to only one client, server should process requests in a serialized way. Now I have two plans to do it: create a thread for each client connection and all the threads take turns accessing the task pool, or use epoll listening on all the connection and process for each event of clients. Which one is better for the job? Or is there any other ideas? The server will be run on a multi-core machine.

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  • SQL: How to order values inside group by

    - by Denis Yaremov
    Consider the following MS SQL Server table: ID | X | Y ------+-------+------- 1 | 1 | 1 2 | 1 | 2 3 | 1 | 3 4 | 2 | 40 5 | 2 | 500 6 | 3 | 1 7 | 3 | 100 8 | 3 | 10 I need to select the ID of the row that has the maximum value of Y grouped by x, i.e: ID | X | Y ------+-------+------- 3 | 1 | 3 5 | 2 | 500 7 | 3 | 100 The query will be nested several times so an optimal performance solution is required... Thank you!

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  • get me the latest Change from Select Query in below given condition

    - by OM The Eternity
    I have a Table structure as id, trackid, table_name, operation, oldvalue, newvalue, field, changedonetime Now if I have 3 rows for the same "trackid" same "field", then how can i select the latest out of the three? i.e. for e.g.: id = 100 trackid = 152 table_name = jos_menu operation= UPDATE oldvalue = IPL newvalue = IPLcccc field = name live = 0 changedonetime = 2010-04-30 17:54:39 and id = 101 trackid = 152 table_name = jos_menu operation= UPDATE oldvalue = IPLcccc newvalue = IPL2222 field = name live = 0 changedonetime = 2010-04-30 18:54:39 As u can see above the secind entry is the latest change, Now what query I should use to get the only one and Latest row out of many such rows... $distupdqry = "select DISTINCT trackid,table_name from jos_audittrail where live = 0 AND operation = 'UPDATE'"; $disupdsel = mysql_query($distupdqry); $t_ids = array(); $t_table = array(); while($row3 = mysql_fetch_array($disupdsel)) { $t_ids[] = $row3['trackid']; $t_table[] = $row3['table_name']; //$t_table[] = $row3['table_name']; } //echo "<pre>";print_r($t_table);echo "<pre>"; //exit; for($n=0;$n<count($t_ids);$n++) { $qupd = "SELECT * FROM jos_audittrail WHERE operation = 'UPDATE' AND trackid=$t_ids[$n] order by changedone DESC "; $seletupdaudit = mysql_query($qupd); $row4 = array(); $audit3 = array(); while($row4 = mysql_fetch_array($seletupdaudit)) { $audit3[] = $row4; } $updatefield = ''; for($j=0;$j<count($audit3);$j++) { if($j == 0) { if($audit3[$j]['operation'] == "UPDATE") { //$insqry .= $audit2[$i]['operation']." "; //echo "<br>"; $updatefield .= "UPDATE `".$audit3[$j]['table_name']."` SET "; } } if($audit3[$j]['operation'] == "UPDATE") { $updatefield .= $audit3[$j]['field']." = '".$audit3[$j]['newvalue']."', "; } } /*echo "<pre>"; print_r($audit3); exit;*/ $primarykey = "SHOW INDEXES FROM `".$t_table[$n]."` WHERE Key_name = 'PRIMARY'"; $prime = mysql_query($primarykey); $pkey = mysql_fetch_array($prime); $updatefield .= "]"; echo $updatefield = str_replace(", ]"," WHERE ".$pkey['Column_name']." = '".$t_ids[$n]."'",$updatefield); } In the above code I am fetching ou the distinct IDs in which update operation has been done, and then accordingly query is fired to get all the changes done on different fields of the selected distinct ids... Here I am creating the Update query by fetching the records from the initially described table which is here mentioned as audittrail table... Therefore I need the last made change in the field so that only latest change can be selected in the select queries i have used... please go through the code.. and see how can i make the required change i need finally..

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  • Do I need to syncronize thread access to an int

    - by Martin Harris
    I've just written a method that is called by multiple threads simultaneously and I need to keep track of when all the threads have completed, the code uses this pattern: private void RunReport() { _reportsRunning++; try { //code to run the report } finally { _reportsRunning--; } } This is the only place within the code that _reportsRunning's value is changed, and the method takes about a second to run. Occasionally when I have more than six or so threads running reports together the final result for _reportsRunning can get down to -1, if I wrap the calls to _runningReports++ and _runningReports-- in a lock then the behaviour appears to be correct and consistant. So, to the question: When I was learning multithreading in C++ I was taught that you didn't need to synchronize calls to increment and decrement operations because they were always one assembly instruction and therefore it was impossible for the thread to be switched out mid-call. Was I taught correctly, and if so how come that doesn't hold true for C#?

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  • Simple C++ container class that is thread-safe for writing

    - by conradlee
    I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none that forms a consensus on a simple solution.

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  • Tomcat 6 thread safe email queue (javax.mail.*)

    - by Eric V
    Hi I have design/architecture question. I would like to send emails from one of my jsp pages. I have one particular issue that has been a little bit of a problem. there is an instance where one of the pages will need to send around 50 emails at near the same time. I would like the messages sent to a queue where a background thread will actually do the email sending. What is the appropriate way to solve this problem? If you know of a tutorial, example code or tomcat configuration is needed please let me know. Thanks,

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