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  • Spring: Using "Lookup method injection" for my ThreadFactory looks not scalable.

    - by Michael Bavin
    Hi, We're building a ThreadFactory so everytime a singleton controller needs a new thread, i get a new instance everytime. Looking at Lookup method injection looks good but what if we have multiple threads. like: public abstract class ThreadManager { public abstract Thread createThreadDoA(); public abstract Thread createThreadDoB(); } and config: <bean id="threadManager" class="bla.ThreadManager" singleton="true"> <lookup-method name="createThreadA" bean="threadA" /> <lookup-method name="createThreadB" bean="threadB"/> </bean> <bean id="threadA" class="bla.ThreadA"> <bean id="threadB" class="bla.ThreadB"> and usage: threadManager.createThreadA(); I don't want to create an abstract "create" method for every new threadclass. Is it possible to make this generich like: threadManager.createThread(ThreadA.class); Thank you

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  • How to avoid SQLiteException locking errors

    - by TheArchedOne
    I'm developing an android app. It has multiple threads reading from and writing to the android SQLite db. I am receiving the following error: SQLiteException: error code 5: database is locked I understand the SQLite locks the entire db on inserting/updating, but these errors only seems to happen when inserting/updating while I'm running a select query. The select query returns a cursor which is being left open quite a wile (a few seconds some times) while I iterate over it. If the select query is not running, I never get the locks. I'm surprised that the select could be locking the db.... is this possible, or is something else going on? What's the best way to avoid such locks? Thanks TAO

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  • How can I run NHibenate queries asynchronously?

    - by andrey-tsykunov
    Hello, One way to increase scalability of the server application is to run IO-bound operation (reading files, sockets, web requests, database requests etc) asynchronously. This does not mean run then in the ThreadPool which will just block threads while operation is being executed. The correct way is to use asynchronous API (BeginRead, BeginGetResponse, BeginExecuteReader etc). The problem is well described in CLR vi C# book. Here is some article about asynchronous queries in Linq to SQL. Are any ways to execute Nhibernate query asynchonously? What about Linq to NHibernate? Thank you, Andrey

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  • C# thread with multiple parameters

    - by Lucas B
    Does anyone know how to pass multiple parameters into a Thread.Start routine? I thought of extending the class, but the C# Thread class is sealed. Here is what I think the code would look like: ... Thread standardTCPServerThread = new Thread(startSocketServerAsThread); standardServerThread.Start( orchestrator, initializeMemberBalance, arg, 60000); ... } static void startSocketServerAsThread(ServiceOrchestrator orchestrator, List<int> memberBalances, string arg, int port) { startSocketServer(orchestrator, memberBalances, arg, port); } Thank you in advance. BTW, I start a number of threads with different orchestrators, balances and ports. Please consider thread safety also.

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  • How to demonstrate java multithreading visibility problems?

    - by Joe23
    If variables in Java are accessed from multiple threads, one must ensure that they are safely published. This usually means using synchronizedor volatile. I have got the impression, that some of my colleagues do not take this issue seriously, since they "never heard of volatile before and their programs have worked for years". So my question is: Can someone provide an example Java program/snippet, that reliably shows data visibility problems. I think running a program and seeing the unexpected NPE or stale variable value would help more, than just theoretic explanations, that cannot be demonstrated. Thanks a lot for your help!

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  • XStream or Simple

    - by Adeel Ansari
    I need to decide on which one to use. My case is pretty simple. I need to convert a simple POJO/Bean to XML, and then back. Nothing special. One thing I am looking for is it should include the parent properties as well. Best would be if it can work on super type, which can be just a marker interface. If anyone can compare these two with cons and pros, and which thing is missing in which one. I know that XStream supports JSON too, thats a plus. But Simple looked simpler in a glance, if we set JSON aside. Whats the future of Simple in terms of development and community? XStream is quite popular I believe, even the word, "XStream", hit many threads on SO. Thanks.

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  • Panel visible=true has no effect

    - by tsilb
    I have a Panel that I'm setting visible=true explicitly. The debugger passes over that line and visible still evaluates to False on the next line. Obviously as a result, the Panel is not shown. How is this possible? pnlValidate.Visible = true; if (IsPostBack) return; <asp:Panel ID="pnlValidate" runat="server"> <asp:Button cssclass="submit2" ID="btnValidate" runat="server" Visible="false" text="Validate" OnClick="btnValidate_Click" /> <br /> <asp:TextBox ID="txt6sql" runat="server" Visible="false" TextMode="multiLine" Width="500" Height="200" ReadOnly="true" ToolTip="Report SQL Statement" /> </asp:Panel> ASP.NET 2.0, no other threads or wonky erratta that "should" be messing with my members.

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  • Is there a Java equivalent to libevent?

    - by JoelPM
    I've written a high-throughput server that handles each request in its own thread. For requests coming in it is occasionally necessary to do RPCs to one or more back-ends. These back-end RPCs are handled by a separate queue and thread-pool, which provides some bounding on the number of threads created and the maximum number of connections to the back-end (it does some caching to reuse clients and save the overhead of constantly creating connections). Having done all this, though, I'm beginning to think an event-based architecture would be more efficient. In searching around I haven't found any equivalents to libevent for Java, but maybe I'm not looking in the right place? Mina-statemachine from Apache was the closest thing I found, but it looks more verbose than I need and there's no real release available. Any suggestions?

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  • How to set classpath in manifest file , while creating JAR from eclipse?

    - by Hippo
    I am trying to creat JAR file through eclipse. I read some of the threads from stackoverflow as well as other forums. But nothing is helping. I have created a separate manifest file like this one. `Manifest-Version: 1.0 Main-Class: Main Class-Path: gnujaxp.jar iText-2.1.5.jar jcalendar.jar jcommon-1.0.16.jar jfreechart-1.0.13.jar jfreechart-1.0.13-experimental.jar jfreechart-1.0.13-swt.jar junit.jar servlet.jar swtgraphics2d.jar tinyos.jar ` I have put all this jars in same project folder. While exporting i am exporting all resources (meants this jar files also.) But still i am getting noclassdeffound error when my application tries to load any one of the jar included. M i wrong anywhere .. Thanks in advance.

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  • Practical non-Turing-complete languages?

    - by Kyle Cronin
    Nearly all programming languages used are Turing Complete, and while this affords the language to represent any computable algorithm, it also comes with its own set of problems. Seeing as all the algorithms I write are intended to halt, I would like to be able to represent them in a language that guarantees they will halt. Regular expressions used for matching strings and finite state machines are used when lexing, but I'm wondering if there's a more general, broadly language that's not Turing complete? edit: I should clarify, by 'general purpose' I don't necessarily want to be able to write all halting algorithms in the language (I don't think that such a language would exist) but I suspect that there are common threads in halting proofs that can be generalized to produce a language in which all algorithms are guaranteed to halt. There's also another way to tackle this problem - eliminate the need for theoretically infinite memory. Once you limit the amount of memory the machine is allowed, the number of states the machine is in is finite and countable, and therefore you can determine if the algorithm will halt (by not allowing the machine to move into a state it's been in before).

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  • Producer/consumer in Grails?

    - by Mulone
    Hi all, I'm trying to implement a Consumer/Producer app in Grails, after several unsuccessful attempts at implementing concurrent threads. Basically I want to store all the events coming from a clients (through separate AJAX calls) in a single queue and then process such a queue in a linear way as soon as new events are added. This looks like a Producer/Consumer problem: http://en.wikipedia.org/wiki/Producer-consumer_problem How can I implement this in Grails (maybe with a timer or even better by generating an event 'process queue')? Basically I'd like to a have a singleton service waiting for new events in the queue and processing them linearly (even if the queue is loaded by several concurrent processes). Any hints? Cheers!

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  • How can I limit access to a particular class to one caller at a time in a web service?

    - by MusiGenesis
    I have a web service method in which I create a particular type of object, use it for a few seconds, and then dispose it. Because of problems arising from multiple threads creating and using instances of this class at the same time, I need to restrict the method so that only one caller at a time ever has one of these objects. To do this, I am creating a private static object: private static object _lock = new object(); ... and then inside the web service method I do this around the critical code: lock (_lock) { using (DangerousObject do = new DangerousObject()) { do.MakeABigMess(); do.CleanItUp(); } } I'm not sure this is working, though. Do I have this right? Will this code ensure that only one instance of DangerousObject is instantiated and in use at a time?

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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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  • Does a multithreaded crawler in Python really speed things up?

    - by beagleguy
    Was looking to write a little web crawler in python. I was starting to investigate writing it as a multithreaded script, one pool of threads downloading and one pool processing results. Due to the GIL would it actually do simultaneous downloading? How does the GIL affect a web crawler? Would each thread pick some data off the socket, then move on to the next thread, let it pick some data off the socket, etc..? Basically I'm asking is doing a multi-threaded crawler in python really going to buy me much performance vs single threaded? thanks!

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  • How to create trunk directory in existing svn repo without a trunk, and move all files to new trunk?

    - by stupakov
    Hi all, I've got an svn repo with no trunk dir. I'd like to create the trunk and branches dirs, and move all my files (currently in the root) into trunk. Creating trunk works just fine: macbook[601] # svn mkdir trunk A trunk macbook[602] # svn commit trunk Adding trunk Committed revision 67. moving everything into trunk fails: macbook[604] # svn move * trunk svn: Cannot copy path 'trunk' into its own child 'trunk/trunk' is there a way to do this without giving it all the file and dir names individually? There are threads describing how to do this with TortoiseSVN, but i'd like to know the right way to do it with the svn commandline. Thanks.

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  • git: Is it possible to save the packed objects of a dry run and push them later?

    - by shovavnik
    I'm trying to push a bunch of commits that contain a lot of code and a few thousand MP3 and PDF files besides (ranging from 5-40 MB each). Git successfully packs the objects: C:\MyProject> git push Counting objects: 7582, done. Delta compression using up to 2 threads. Compressing objects: 100% (7510/7510), done. But it fails to send the push for some as yet unknown reason. The problem is that it takes it a very long time to repack the files (I'm on a battery-powered laptop and it took about 20 minutes to pack). So I guess my question can be phrases thus: Is it possible to save the packed objects created in a dry run? Once saved, is it possible to push those packed objects and avoid repacking? I looked it up in the git manual and elsewhere and couldn't find anything conclusive. Any help or pointers are appreciated.

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  • Implementing a Mutex Lock in C

    - by Adam
    I'm trying to make a really mutex in C and for some reason I'm getting cases where two threads are getting the lock at the same time, which shouldn't be possible. Any ideas why it's not working? void mutexLock(mutex_t *mutexlock, pid_t owner) { int failure; while(mutexlock->mx_state == 0 || failure || mutexlock->mx_owner != owner) { failure = 1; if (mutexlock->mx_state == 0) { asm( "test:" "movl $0x01,%%eax\n\t" // move 1 to eax "xchg %%eax,%0\n\t" // try to set the lock bit "mov %%eax,%1\n\t" // export our result to a test var "test %%eax,%%eax\n\t" "jnz test\n\t" :"=r"(mutexlock->mx_state),"=r"(failure) :"r"(mutexlock->mx_state) :"%eax" ); } if (failure == 0) { mutexlock->mx_owner = owner; //test to see if we got the lock bit } } }

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  • How is thread synchronization implemented, at the assembly language level?

    - by Martin
    While I'm familiar with concurrent programming concepts such as mutexes and semaphores, I have never understood how they are implemented at the assembly language level. I imagine there being a set of memory "flags" saying: lock A is held by thread 1 lock B is held by thread 3 lock C is not held by any thread etc But how is access to these flags synchronized between threads? Something like this naive example would only create a race condition: mov edx, [myThreadId] wait: cmp [lock], 0 jne wait mov [lock], edx ; I wanted an exclusive lock but the above ; three instructions are not an atomic operation :(

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  • java I/O is blocked while reading on socket when i put off the battery from device.

    - by gunjan goyal
    hi, i m working on client socket connection. client is a GPRS hardware device. i m receiving request from this client on my serversocket and then opening multiple threads. my problem is that when device/client close the socket then my IO detects that throws an exception but when i put off the battery from the device while sending the request to the serversocket it is blocked without throwing any exception. please help me out. thanks in advance. this is my code. try { while ((len = inputStream.read(mainBuffer)) -1) { System.out.println("len= " + len); }//end of while System.out.println("out of while loop");//which is never printed on screen. } catch (IOException e) { e.printStackTrace(); } regards gunjan goyal

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  • Sequence Diagram Reverse Engineering Tool?

    - by Wayne
    It's essential for me to find a tool that will reverse engineer sequence diagrams by integrating with the debugger. I suppose using the profiler could work also but less desirable. It's a key requirement that the tool in question will record all threads of execution since the app, TickZoom, is heavily parallelized. We just evaluated a most awesome tool from Sparx called Enterprise Architect which integrates with the debugger. It allows you to set a break point, start recording method traces from that break point. It's a lovely design and GUI. Hope it works for you but it only records a single thread of execution so that makes it unusable for us. I will put in a feature request to Sparx. But hope to find a similar tool that already does this since that's the only feature we need--not all the other amazing features that Sparx Enterprise Architect appears to do rather well.

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  • How can I limit access to a particular class to one caller at a time in an ASMX web service?

    - by MusiGenesis
    I have a web service method in which I create a particular type of object, use it for a few seconds, and then dispose it. Because of problems arising from multiple threads creating and using instances of this class at the same time, I need to restrict the method so that only one caller at a time ever has one of these objects. To do this, I am creating a private static object: private static object _lock = new object(); ... and then inside the web service method I do this around the critical code: lock (_lock) { using (DangerousObject do = new DangerousObject()) { do.MakeABigMess(); do.CleanItUp(); } } I'm not sure this is working, though. Do I have this right? Will this code ensure that only one instance of DangerousObject is instantiated and in use at a time? Or does each caller get their own copy of _lock, rendering my code here laughable?

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  • Spring - scheduling and pooling runnables of different state (each Runnable instance has different

    - by lisak
    Hi, I can't figure out what to use for scheduling and pooling runnables of different state (each Runnable instance has different state). I could use ScheduledExecutorFactoryBean together with MethodInvokingRunnable to supply arguments. But take a look at the key ScheduledExecutorFactoryBean method, it is designed in a way that all task should start at the beginning. protected void registerTasks(ScheduledExecutorTask[] tasks, ScheduledExecutorService executor) { for (ScheduledExecutorTask task : tasks) { Runnable runnable = getRunnableToSchedule(task); if (task.isOneTimeTask()) { executor.schedule(runnable, task.getDelay(), task.getTimeUnit()); } else { if (task.isFixedRate()) { executor.scheduleAtFixedRate(runnable, task.getDelay(), task.getPeriod(), task.getTimeUnit()); } else { executor.scheduleWithFixedDelay(runnable, task.getDelay(), task.getPeriod(), task.getTimeUnit()); } } } } I can't think of how to setup this scenario with ThreadPoolTaskScheduler. Please help me out here. Thank you EDIT: shortened version is: how to setup task scheduler that would run hundreds of "different instances of Threads (with different state) with 2 seconds interval.

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  • Help with SQL Join on two tables

    - by bladefist
    I have two tables, one is a table of forum threads. It has a last post date column. Another table has PostID, UserId, and DateViewed. I want to join these tables so I can compare DateViewed and LastPostDate for the current user. However, if they have never viewed the thread, there will not be a row in the 2nd table. This seems easy but I cant wrap my head around it. Advice please. Thanks in advance.

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  • Form gets disposed somehow

    - by mnn
    I have a client-server application, in which I use classic Sockets and threads for receiving/sending data and listening for clients. The application works fine, but after some random time I get the ObjectDisposedException: System.ObjectDisposedException: Cannot access a disposed object. Object name: 'MainForm'. at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous) at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args) at System.Windows.Forms.Control.Invoke(Delegate method) That code is called from client Socket thread and I use Invoke() method to run the code on UI thread. I'm sure that I don't manually dispose the form nor using Close() (form is closed by user clicking Close button), so I don't know what could cause its disposing.

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  • How do you implement Software Transactional Memory?

    - by Joseph Garvin
    In terms of actual low level atomic instructions and memory fences (I assume they're used), how do you implement STM? The part that's mysterious to me is that given some arbitrary chunk of code, you need a way to go back afterward and determine if the values used in each step were valid. How do you do that, and how do you do it efficiently? This would also seem to suggest that just like any other 'locking' solution you want to keep your critical sections as small as possible (to decrease the probability of a conflict), am I right? Also, can STM simply detect "another thread entered this area while the computation was executing, therefore the computation is invalid" or can it actually detect whether clobbered values were used (and thus by luck sometimes two threads may execute the same critical section simultaneously without need for rollback)?

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