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• Where is the chink in Google Chrome's armor?

  - by kudlur

  While browsing with Chrome, I noticed that it responds extremely fast (in comparison with IE and Firefox on my laptop) in terms of rendering pages, including JavaScript heavy sites like gmail. This is what googlebook on Chrome has to say tabs are hosted in process rather than thread. compile javascript using V8 engine as opposed to interpreting. Introduce new virtual machine to support javascript heavy apps introduce "hidden class transitions" and apply dynamic optimization to speed up things. Replace inefficient "Conservative garbage colllection" scheme with more precise garbage collection scheme. Introduce their own task scheduler and memory manager to manage the browser environment. All this sounds so familiar, and Microsoft has been doing such things for long time.. Windows os, C++, C# etc compilers, CLR, and so on. So why isn't Microsoft or any other browser vendor taking Chrome's approach? Is there a flaw in Chrome's approach? If not, is the rest of browser vendor community caught unaware with Google's approach?

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• Creating TCP network errors for unit testing

  - by Robert S. Barnes

  I'd like to create various network errors during testing. I'm using the Berkely sockets API directly in C++ on Linux. I'm running a mock server in another thread from within Boost.Test which listens on localhost. For instance, I'd like to create a timeout during connect. So far I've tried not calling accept in my mock server and setting the backlog to 1, then making multiple connections, but all seem to successfully connect. I would think that if there wasn't room in the backlog queue I would at least get a connection refused error if not a timeout. I'd like to do this all programatically if possible, but I'd consider using something external like IPchains to intentionally drop certain packets to certain ports during testing, but I'd need to automate creating and removing rules so I could do it from within my Boost.Test unit tests. I suppose I could mock the various system calls involved, but I'd rather go through a real TCP stack if possible. Ideas?

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• How does the default Camera iPhone app manages to save a photo so fast?

  - by worriorbg

  Hello everyone. So far I've managed to create an app for iPhone that takes multiple images with about a 3 second interval between each. I`m processing each image in a separate thread asynchronously and everything is great till it gets to the moment for saving the image on the iPhone disk. Then it takes about 12 seconds to save the image to the disk using JPEG representation. How does Apple do it, how do they manage to save a single image so fast to the disk is there a trick they are using? I saw that the animations distract the user for a while, but still the time needed is below 12 seconds! Thanks in advance.

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• NoClassDefFoundError when running java tool under Xcode

  - by pancake

  Hi all, I'm trying to create a Java Tool by using Xcode. I've already changed my build.xml to have Xcode target java 1.6 and not 1.3 so I can use generics. I'm getting no build errors and using 'javac' and 'java' in the terminal works. Now I want it to work in Xcode as well. I keep getting the following error: Exception in thread "main" java.lang.NoClassDefFoundError: MyClass where 'MyClass' is the class containing the main method. It probably has something to do with the classpath, which as the build.xml prescribes is "${bin}". There is a bin folder in my project folder, and it contains all the .class files needed to run the program. If anybody could help me, it'd be great!

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• SQL Compact Edition 3.5 SP 1 - LockTimeOutException - how to debug?

  - by Bob King

  Intermittently in our app, we encounter LockTimeoutExceptions being throw from SQL CE. We've recently upgraded to 3.5 SP 1, and a number of them seem to have gone away, but we still do see them occasionally. I'm certain it's a bug in our code (which is multi-threaded) but I haven't been able to pin it down precisely. Does anyone have any good techniques for debugging this problem? The exceptions log like this (there's never a stack trace for these exceptions): SQL Server Compact timed out waiting for a lock. The default lock time is 2000ms for devices and 5000ms for desktops. The default lock timeout can be increased in the connection string using the ssce: default lock timeout property. [ Session id = 6,Thread id = 7856,Process id = 10116,Table name = Product,Conflict type = s lock (x blocks),Resource = DDL ] Our database is read-heavy, but does seldom writes, and I think I've got everything protected where it needs to be. EDIT: SQL CE already automatically uses NOLOCK http://msdn.microsoft.com/en-us/library/ms172398(sql.90).aspx

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• Rails 2.3.5: How does one add an error when it doesn't make sense to put it in a validation?

  - by randombits

  I recently was trying to add errors.add_to_base code in the middle of some model logic and was wondering why it wasn't showing up in my view that was iterating over all errors. I then ran across this e-mail which explains why: http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/e045ec1dead1ff06?pli=1 The question is then, how does one add errors with add_to_base if it doesn't make sense to put them into a validate method? I have some complex logic. The model needs to talk to a has_many relationship which has its own relationships that go through a myriad of conditionals to figure out if a request makes sense. It's nothing that can be tied to a validate method easily. How does one add errors then accordingly?

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• Silverlight 4 Multithread

  - by DavyMac23

  I'm trying to update my Silverlight 4 UI approx every 1/2 second with new data. I've hooked into a WCF service using net.tcp binding and issuing callbacks from the server. To make sure I get the data from the service as quickly as possible I've started up my proxy on a backround worker inside of my Silverlight App. My question is, how do I get the results from the callback and update the ObservableCollection that is bound to a datagird? I've tried a number of different ways and keep getting the dreaded cross-thread error.

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• Triggering Quartz job from JSF (Any front end)- How to wait for the job execution to be over

  - by Maximus

  I am developing a front end to trigger a quartz job on the fly. I have a form in the JSF page whose click action will dynamically trigger a quartz job. The job is invoked by the following statement, the job is triggered and everything works fine. scheduler.triggerJob("Job1",Scheduler.DEFAULT_GROUP,jobDataMap); From what I understand the job seems to run in a separate thread and the execution of the calling function does not wait for the job to be over. Since I am invoking the job from front end, I would like to wait till the job is over before I navigate to a different JSF page. So I can display an error message if the job fails. I would also like to display a message to the user, "Processing job, please wait.." until the job is actually over. Any ideas on how to accomplish this will be appreciated. Thanks !

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• How to handle recurring execution?

  - by ShaneC

  I am trying to validate the solution I came up for what I think is a fairly typical problem. I have a service running and every 10 minutes it should do something. I've ended up with the following: private bool isRunning = true; public void Execute() { while(isRunning) { if(isRunning) { DoSomething(); m_AutoResetEvent.WaitOne(new Timespan(0, 10, 0)); } } } public void Stop() { isRunning = false; m_AutoResetEvent.Set(); } The immediate potential problems I can see is that I'm not doing any sort of locking around the isRunning modification in Stop() which gets called by another thread but I'm not sure I really need to? The worst that I think could happen is that it runs one extra cycle. Beyond that are there any obvious problems with this code? Is there a better way to solve this problem that I'm unaware of?

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• Multithreading with STL container

  - by Steven

  I have an unordered map which stores a pointer of objects. I am not sure whether I am doing the correct thing to maintain the thread safety. typedef std::unordered_map<string, classA*>MAP1; MAP1 map1; pthread_mutex_lock(&mutexA) if(map1.find(id) != map1.end()) { pthread_mutex_unlock(&mutexA); //already exist, not adding items } else { classA* obj1 = new classA; map1[id] = obj1; obj1->obtainMutex(); //Should I create a mutex for each object so that I could obtain mutex when I am going to update fields for obj1? pthread_mutex_unlock(&mutexA); //release mutex for unordered_map so that other threads could access other object obj1->field1 = 1; performOperation(obj1); //takes some time obj1->releaseMutex(); //release mutex after updating obj1 }

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• Invoking a superclass's class methods in Python

  - by LeafStorm

  I am working on a Flask extension that adds CouchDB support to Flask. To make it easier, I have subclassed couchdb.mapping.Document so the store and load methods can use the current thread-local database. Right now, my code looks like this: class Document(mapping.Document): # rest of the methods omitted for brevity @classmethod def load(cls, id, db=None): return mapping.Document.load(cls, db or g.couch, id) I left out some for brevity, but that's the important part. However, due to the way classmethod works, when I try to call this method, I receive the error message File "flaskext/couchdb.py", line 187, in load return mapping.Document.load(cls, db or g.couch, id) TypeError: load() takes exactly 3 arguments (4 given) I tested replacing the call with mapping.Document.load.im_func(cls, db or g.couch, id), and it works, but I'm not particularly happy about accessing the internal im_ attributes (even though they are documented). Does anyone have a more elegant way to handle this?

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• Combining RequiresSTA and Timeout attributes on a test fails

  - by Peter Lillevold

  I have a test that opens and closes a WPF Window and thus requires the STA threading apartment. To safeguard the test against the window staying open (and thus hang the test indefinitely) I wanted to use the Timeout attribute. The problem is that applying the Timeout attribute causes the test to fail on timeout regardless of whether the test works or not. Without the attribute everything works fine. My theory is that Timeout causes the test to be executed on a new thread that does not inherit the STA apartment. Is there another way to have both STA and the timeout safeguard in NUnit? My test looks something like this: [Test, RequiresSTA, Timeout(300)] public void Construct() { var window = new WindowView(); window.Loaded += (sender, args) => window.Close(); var app = new Application(); app.Run(window); try { // ...run system under test } finally { app.Shutdown(); } }

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• IIS 7 problem which does not occur under apache

  - by cc0

  I'm hosting a little site using a JavaScript to draw a simple graph. It involves one html index file, some css and some js files. It has all been working perfectly on two different apache servers, but when I set up IIS 7 the ajax calls fail. I get no java debug errors in firefox that I can work with, or any kind of error message at all. Without going into the code itself, does anyone have a similar experience with IIS? This is the first time I'm using IIS so I'm not quite sure what to expect to have trouble with. I'd love some input on this, if I have to delve into the code itself I'll make a new thread, I just thought I'd see if this could be a typical issue. Any help is appreciated!

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• How do I fix "java.lang.OutOfMemoryError at sun.misc.Unsafe.allocateMemory(Native Method)"?

  - by Jephir

  I'm making a Java application that uses the Slick library to load images. However, on some computers, I get this error when trying to run the program: Exception in thread "main" java.lang.OutOfMemoryError at sun.misc.Unsafe.allocateMemory(Native Method) at java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:99) at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:288) at org.lwjgl.BufferUtils.createByteBuffer(BufferUtils.java:60) at org.newdawn.slick.opengl.PNGImageData.loadImage(PNGImageData.java:692) at org.newdawn.slick.opengl.CompositeImageData.loadImage(CompositeImageData.java:62) at org.newdawn.slick.opengl.CompositeImageData.loadImage(CompositeImageData.java:43) My VM options are: -Djava.library.path=lib -Xms1024M -Xmx1024M -XX:PermSize=256M -XX:MaxPermSize=256M The program loads a few large images (1024 x 768 resolution) at the beginning. Any help to solve this problem would be greatly appreciated.

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• How to make IIS wait for WCF service gets ready?

  - by Kamarey

  I have a WCF service hosted in IIS 7. It takes some minutes until this service finish to load its data and ready for external calls. Data loads in internal thread. The problem is that from IIS point the service is ready just after it was activated (by some call), and it process a request without waiting for data to be loaded. Is it possible to tell IIS that the service is still loading and make this service unavailable for requests? No problem if such request will throw an exception.

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• Can Parallel.ForEach be used safely with CloudTableQuery

  - by knightpfhor

  I have a reasonable number of records in an Azure Table that I'm attempting to do some one time data encryption on. I thought that I could speed things up by using a Parallel.ForEach. Also because there are more than 1K records and I don't want to mess around with continuation tokens myself I'm using a CloudTableQuery to get my enumerator. My problem is that some of my records have been double encrypted and I realised that I'm not sure how thread safe the enumerator returned by CloudTableQuery.Execute() is. Has anyone else out there had any experience with this combination?

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• Can an application's Service ever run in a different process?

  - by kpdvx

  If an application begins a Service via bindService or startService, will this Service object ever run from a process different from that of the application? I ask because many Android example projects begin a service and communicate to them using IPC which seems wholly unnecessary considering that, according to the Android Service documentation, "... services, like other application objects, run in the main thread of their hosting process." IPC, AIDL, and the IBinder interface only seem useful if connecting to a Service started by an application other than your own. Is this a correct or fair understanding?

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• Is select() Ok to implement single socket read/write timeout ?

  - by chmike

  I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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• Which method should I use to give the perception the computer is thinking in programming?

  - by Roy

  I want to create a simple game like tic tac toe where the human user is playing against the computer. The computer function takes a couple of milliseconds to run but I would like to make the computer take 5 seconds to make a move. Which method should I use? 1) Create two memory threads. One for the computer and one for the human user. When the computer is taking 5 seconds to imitate thinking, the human user thread is paused for 5 seconds. 2) Disable input devices for 5 seconds using timer or dispatchertimer 3) Any better methods you can think of Thanks!

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• Should I be worried about sending Apk to client before getting paid?

  - by DanielS

  I am working on an Android app for a client. The app is practically finished, and next week I'll have a meeting with the client to present it. He'll test everything, and upon approving it he will make the payment and I'll give him the source code and publish it on Google Play. Today he called me asking for the Apk so that he can start testing it. I am worried that if we don't close the deal (for one reason or another) he might get someone to reverse engineer the Apk and get my source code/app anyway, even if obfuscated with ProGuard (I never tried, but according to this SO thread it's not that difficult to reverse engineer an Apk). My question: Am I being paranoid here and should just send the client the Apk (cause perhaps the ProGuard obfuscation is enough to make the source code useless) , or are my worries reasonable and I should stick to getting paid before delivering anything?

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• How to design a client server architect

  - by Saurabh01

  I like to know the server (TCP based) architecture to support large scale of clients(at least10K) to implement Fix server. My points are How we design it. How to listen on the open port? Use select or poll or any other function. How to process the response of the client? On large scale we cannot create the one thread for each client. Should the processing of response is in the different executable and share the request and response to the server executable through IPC. There is much more on it. I would appreciate if anyone explains it or provide any link. Thanks

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• Python/Tkinter make a custom window

  - by user1435947

  I want to make a window without the top taskbar (that is movable), so there is only thin outline around the GUI box. I also want to add my own 'X' to the box. import Tkinter class Application(Frame): def __init__(self, master=None): Frame.__init__(self, master) self.parent = master ............ def main(): root = Tk() root.attributes('-fullscreen', True) root.geometry('500x250+500+200') app = Application(root) app.parent.configure(background = 'gray32') root.resizable(width=FALSE, height=FALSE) app.mainloop() main() I tried forcing the box to resize after going into fullscreen to remove the taskbar, though box is no longer movable. Any suggestions? [I have seen this thread: Python/Tkinter: Removing/disabling a resizable window's maximize button under Windows The -toolwindow attribute didn't work for me, maybe because I use linux...]

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• How does jQuery have asynchronous functions?

  - by Sam.Rueby

  I'm surprised I can't find a clear answer to this. So, in jQuery, you can do this: $(someElements).fadeOut(1000); $(someElements).remove(); Which, will start a fadeOut animation, but before it finishes executing in the 1 second duration, the elements are removed from the DOM. But how is this possible? I keep reading the JavaScript is single threaded. ( Is javascript guaranteed to be single-threaded? ) This question is not "How do I fix this?" I know I can do either: $(someElements).fadeOut(1000).promise().done(function() { $(someElements).remove();});, or even better:$(someElements).fadeOut(1000, function() { $(this).remove(); } ); What I don't understand is how JavaScript runs in a "single thread" but I'm able to use these jQuery functions that execute asynchronously and visibly see the DOM change in different places at the same time. How does it work?

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• qapps runs well but breakpoint sometimes generates segmentation fault

  - by yan bellavance

  I have a qApp that generates a segmentation fault only when a breakpoint is inserted in the code (I can put it at different places) and only after 4-5 breakpoint stops. Do I have a problem with my code or is this a DBG bug. the method is part of a QThread Class. Basically what I did is i took the mandlebrot example, and have 3 instances of it in my program. So the program would look like a mainwindow that has 3 mandlebrot widgets in it, one besides the other. Is it possible that GDB doesnt support debugging qthread subclasses that are instantiated multiple times or is it thread-unsafe to do so. I dont have any problems at run-time.

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• Can't catch newConnection() signal from QTcpServer

  - by Bob

  I am trying to make a simple server thread in QT to accept a connection, however although the server is listening (I can connect with my test app) I can't get the newConnection() signal to be acted on. Any help as to what I'm missing here would be much appreciated! class CServerThread : public QThread { Q_OBJECT protected: void run(); private: QTcpServer* server; public slots: void AcceptConnection(); }; void CServerThread::run() { server = new QTcpServer; QObject::connect(server, SIGNAL(newConnection()), this, SLOT(AcceptConnection())); server-listen(QHostAddress::Any, 1000); // Any port in a storm exec(); // Start event loop } void CServerThread::AcceptConnection() { OutputDebugStringA("\n***** INCOMING CONNECTION"); // This is never called! }

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