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  • Web image loaded by thread in android

    - by Bostjan
    I have an extended BaseAdapter in a ListActivity: private static class RequestAdapter extends BaseAdapter { and some handlers and runnables defined in it // Need handler for callbacks to the UI thread final Handler mHandler = new Handler(); // Create runnable for posting final Runnable mUpdateResults = new Runnable() { public void run() { loadAvatar(); } }; protected static void loadAvatar() { // TODO Auto-generated method stub //ava.setImageBitmap(getImageBitmap("URL"+pic)); buddyIcon.setImageBitmap(avatar); } In the getView function of the Adapter, I'm getting the view like this: if (convertView == null) { convertView = mInflater.inflate(R.layout.messageitem, null); // Creates a ViewHolder and store references to the two children views // we want to bind data to. holder = new ViewHolder(); holder.username = (TextView) convertView.findViewById(R.id.username); holder.date = (TextView) convertView.findViewById(R.id.dateValue); holder.time = (TextView) convertView.findViewById(R.id.timeValue); holder.notType = (TextView) convertView.findViewById(R.id.notType); holder.newMsg = (ImageView) convertView.findViewById(R.id.newMsg); holder.realUsername = (TextView) convertView.findViewById(R.id.realUsername); holder.replied = (ImageView) convertView.findViewById(R.id.replied); holder.msgID = (TextView) convertView.findViewById(R.id.msgID_fr); holder.avatar = (ImageView) convertView.findViewById(R.id.buddyIcon); holder.msgPreview = (TextView) convertView.findViewById(R.id.msgPreview); convertView.setTag(holder); } else { // Get the ViewHolder back to get fast access to the TextView // and the ImageView. holder = (ViewHolder) convertView.getTag(); } and the image is getting loaded this way: Thread sepThread = new Thread() { public void run() { String ava; ava = request[8].replace(".", "_micro."); Log.e("ava thread",ava+", username: "+request[0]); avatar = getImageBitmap(URL+ava); buddyIcon = holder.avatar; mHandler.post(mUpdateResults); //holder.avatar.setImageBitmap(getImageBitmap(URL+ava)); } }; sepThread.start(); Now, the problem I'm having is that if there are more items that need to display the same picture, not all of those pictures get displayed. When you scroll up and down the list maybe you end up filling all of them. When I tried the commented out line (holder.avatar.setImageBitmap...) the app sometimes force closes with "only the thread that created the view can request...". But only sometimes. Any idea how I can fix this? Either option.

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  • Linker Issues with boost::thread under linux using Eclipse and CMake

    - by OcularProgrammer
    I'm in the process of attempting to port some code across from PC to Ubuntu, and am having some issues due to limited experience developing under linux. We use CMake to generate all our build stuff. Under windows I'm making VS2010 projects, and under Linux I'm making Eclipse projects. I've managed to get my OpenCV stuff ported across successfully, but am having major headaches trying to port my threaded boost apps. Just so we're clear, the steps I have followed so-far on a clean Ubuntu 12 installation. (I've done 2 clean re-installs to try and fix potential library cock-ups, now I'm just giving up and asking): Install Eclipse and Eclipse CDT using my package manager Install CMake and CMake Gui using my package manager Install libboost-all-dev using my package manager So-far that's all I've done. I can create the eclipse project using CMake with no errors, so CMake is successfully finding my boost install. When I try and build through eclipse is when I get issues; The app I'm attempting to build uses boost::asio for some UDP I/O and boost::thread to create worker threads for the asio I/O services. I can successfully compile each module, but when I come to link I get spammed with errors such as: /usr/bin/c++ CMakeFiles/RE05DevelopmentDemo.dir/main.cpp.o CMakeFiles/RE05DevelopmentDemo.dir/RE05FusionListener/RE05FusionListener.cpp.o CMakeFiles/RE05DevelopmentDemo.dir/NewEye/NewEye.cpp.o -o RE05DevelopmentDemo -rdynamic -Wl,-Bstatic -lboost_system-mt -lboost_date_time-mt -lboost_regex-mt -lboost_thread-mt -Wl,-Bdynamic /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `void boost::call_once<void (*)()>(boost::once_flag&, void (*)()) [clone .constprop.98]': make[2]: Leaving directory `/home/david/Code/Build/Support/RE05DevDemo' (.text+0xc8): undefined reference to `pthread_key_create' /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `boost::this_thread::interruption_enabled()': (.text+0x540): undefined reference to `pthread_getspecific' make[1]: Leaving directory `/home/david/Code/Build/Support/RE05DevDemo' /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `boost::this_thread::disable_interruption::disable_interruption()': (.text+0x570): undefined reference to `pthread_getspecific' /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `boost::this_thread::disable_interruption::disable_interruption()': (.text+0x59f): undefined reference to `pthread_getspecific' Some Gotchas that I have collected from other StackOverflow posts and have already checked: The boost libs are all present at /usr/lib I am not getting any compile errors for inability to find the boost headers, so they must be getting found. I am trying to link statically, but I believe eclipse should be passing the correct arguments to make that happen since my CMakeLists.txt includes SET(Boost_USE_STATIC_LIBS ON) I'm officially out of ideas here, I have tried doing local builds of boost and a bunch of other stuff with no more success. I even re-installed Ubuntu to ensure I haven't completely fracked the libs directories and links with multiple weird versions or anything else. Any help would be muchly appreciated.

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  • efficient thread-safe singleton in C++

    - by user168715
    The usual pattern for a singleton class is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) inst = new Foo(...); return *inst; } However, it's my understanding that this solution is not thread-safe, since 1) Foo's constructor might be called more than once (which may or may not matter) and 2) inst may not be fully constructed before it is returned to a different thread. One solution is to wrap a mutex around the whole method, but then I'm paying for synchronization overhead long after I actually need it. An alternative is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) { pthread_mutex_lock(&mutex); if(inst == NULL) inst = new Foo(...); pthread_mutex_unlock(&mutex); } return *inst; } Is this the right way to do it, or are there any pitfalls I should be aware of? For instance, are there any static initialization order problems that might occur, i.e. is inst always guaranteed to be NULL the first time getInst is called?

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  • Apply [ThreadStatic] attribute to a method in external assembly

    - by Sen Jacob
    Can I use an external assembly's static method like [ThreadStatic] method? Here is my situation. The assembly class (which I do not have access to its source) has this structure public class RegistrationManager() { private RegistrationManager() {} public static void RegisterConfiguration(int ID) {} public static object DoWork() {} public static void UnregisterConfiguration(int ID) {} } Once registered, I cannot call the DoWork() with a different ID without unregistering the previously registered one. Actually I want to call the DoWork() method with different IDs simultaneously with multi-threading. If the RegisterConfiguration(int ID) method was [ThreadStatic], I could have call it in different threads without problems with calls, right? So, can I apply the [ThreadStatic] attribute to this method or is there any other way I can call the two static methods same time without waiting for other thread to unregister it? If I check it like the following, it should work. for(int i=0; i < 10; i++) { new Thread(new ThreadStart(() => Checker(i))).Start(); } public string Checker(int i) { public static void RegisterConfiguration(i); // Now i cannot register second time public static object DoWork(i); Thread.Sleep(5000); // DoWork() may take a little while to complete before unregistered public static void UnregisterConfiguration(i); }

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  • (static initialization order?!) problems with factory pattern

    - by smerlin
    Why does following code raise an exception (in createObjects call to map::at) alternativly the code (and its output) can be viewed here intererestingly the code works as expected if the commented lines are uncommented with both microsoft and gcc compiler (see here), this even works with initMap as ordinary static variable instead of static getter. The only reason for this i can think of is that the order of initialization of the static registerHelper_ object (factory_helper_)and the std::map object (initMap) are wrong, however i cant see how that could happen, because the map object is constructed on first usage and thats in factory_helper_ constructor, so everything should be alright shouldnt it ? I am even more suprised that those doNothing() lines fix the issue, because that call to doNothing() would happen after the critical section (which currently fails) is passed anyway. EDIT: debugging showed, that without the call to factory_helper_.doNothing(), the constructor of factory_helper_ is never called. #include <iostream> #include <string> #include <map> #define FACTORY_CLASS(classtype) \ extern const char classtype##_name_[] = #classtype; \ class classtype : FactoryBase<classtype,classtype##_name_> namespace detail_ { class registerHelperBase { public: registerHelperBase(){} protected: static std::map<std::string, void * (*)(void)>& getInitMap() { static std::map<std::string, void * (*)(void)>* initMap = 0; if(!initMap) initMap= new std::map<std::string, void * (*)(void)>(); return *initMap; } }; template<class TParent, const char* ClassName> class registerHelper_ : registerHelperBase { static registerHelper_ help_; public: //void doNothing(){} registerHelper_(){ getInitMap()[std::string(ClassName)]=&TParent::factory_init_; } }; template<class TParent, const char* ClassName> registerHelper_<TParent,ClassName> registerHelper_<TParent,ClassName>::help_; } class Factory : detail_::registerHelperBase { private: Factory(); public: static void* createObject(const std::string& objclassname) { return getInitMap().at(objclassname)(); } }; template <class TClass, const char* ClassName> class FactoryBase { private: static detail_::registerHelper_<FactoryBase<TClass,ClassName>,ClassName> factory_helper_; static void* factory_init_(){ return new TClass();} public: friend class detail_::registerHelper_<FactoryBase<TClass,ClassName>,ClassName>; FactoryBase(){ //factory_helper_.doNothing(); } virtual ~FactoryBase(){}; }; template <class TClass, const char* ClassName> detail_::registerHelper_<FactoryBase<TClass,ClassName>,ClassName> FactoryBase<TClass,ClassName>::factory_helper_; FACTORY_CLASS(Test) { public: Test(){} }; int main(int argc, char** argv) { try { Test* test = (Test*) Factory::createObject("Test"); } catch(const std::exception& ex) { std::cerr << "caught std::exception: "<< ex.what() << std::endl; } #ifdef _MSC_VER system("pause"); #endif return 0; }

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  • android shut-down errors / thread problems

    - by iQue
    Im starting to deal with some stuff in my game that I thought were "minor problems" and one of these are that I get an error every time I shut down my game that looks like this: 09-05 21:40:58.320: E/AndroidRuntime(30401): FATAL EXCEPTION: Thread-4898 09-05 21:40:58.320: E/AndroidRuntime(30401): java.lang.NullPointerException 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainGamePanel.render(MainGamePanel.java:94) 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainThread.run(MainThread.java:101) on these lines is my GameViews rendering-method and the line in my Thread that calls my GameViews rendering-method. Im guessing Something in my surfaceDestroyed(SurfaceHolder holder) is wrong, or maybe Im not ending the tread in the right place. My surfaceDestroyed-method: public void surfaceDestroyed(SurfaceHolder holder) { Log.d(TAG, "Surface is being destroyed"); boolean retry = true; ((MainThread)thread).setRunning(false); while (retry) { try { ((MainThread)thread).join(); retry = false; } catch (InterruptedException e) { } } Log.d(TAG, "Thread was shut down cleanly"); } Also, In my activity for this View my onPaus, onDestoy and onStop are empty, do I maybe need to add something there? The crash occurs when I press my home-button on the phone, or any other button that makes the game stop. But as I understand it the onPaus is called when you press the Home-button.. This is really new territory for me so Im sorry if im missing something obvious or something really big. adding my surfaceCreated method asweel since that is where I start this thread: public void surfaceCreated(SurfaceHolder holder) { controls = new GameControls(this); setOnTouchListener(controls); timer1.schedule(new Task(this), 0, delay1); thread.setRunning(true); thread.start(); } and aslong as this is running, my game is rendering and updating.

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  • non-static method cannot be referenced from a static context

    - by Mith
    I am modifying the source code here: http://thinkandroid.wordpress.com/2009/12/30/getting-response-body-of-httpresponse/ I get this error: non-static method getContentCharSet(org.apache.http.HttpEntity) cannot be referenced from a static context String charset = getContentCharSet(entity); This error is line 13 on the second box. Any ideas? I have been really struggling with this code :-(

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  • Can static methods be called using object/instance in .NET

    Ans is Yes and No   Yes in C++, Java and VB.NET No in C#   This is only compiler restriction in c#. You might see in some websites that we can break this restriction using reflection and delegates, but we can’t, according to my little research J I shall try to explain you…   Following is code sample to break this rule using reflection, it seems that it is possible to call a static method using an object, p1 using System; namespace T {     class Program     {         static void Main()         {             var p1 = new Person() { Name = "Smith" };             typeof(Person).GetMethod("TestStatMethod").Invoke(p1, new object[] { });                     }         class Person         {             public string Name { get; set; }             public static void TestStatMethod()             {                 Console.WriteLine("Hello");             }         }     } } but I do not think so this method is being called using p1 rather Type Name “Person”. I shall try to prove this… look at another example…  Test2 has been inherited from Test1. Let’s see various scenarios… Scenario1 using System; namespace T {     class Program     {         static void Main()         {             Test1 t = new Test1();            typeof(Test2).GetMethod("Method1").Invoke(t,                                  new object[] { });         }     }     class Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method1");         }     }       class Test2 : Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method2");         }     } } Output:   At test1::Method2 Scenario2         static void Main()         {             Test2 t = new Test2();            typeof(Test2).GetMethod("Method1").Invoke(t,                                          new object[] { });         }   Output:   At test1::Method2   Scenario3         static void Main()         {             Test1 t = new Test2();            typeof(Test2).GetMethod("Method1").Invoke(t,                             new object[] { });         }   Output: At test1::Method2 In all above scenarios output is same, that means, Reflection also not considering the object what you pass to Invoke method in case of static methods. It is always considering the type which you specify in typeof(). So, what is the use passing instance to “Invoke”. Let see below sample using System; namespace T {     class Program     {         static void Main()         {            typeof(Test2).GetMethod("Method1").                Invoke(null, new object[] { });         }     }       class Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method1");         }     }     class Test2 : Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method2");         }     } }   Output is   At test1::Method2   I was able to call Invoke “Method1” of Test2 without any object.  Yes, there no wonder here as Method1 is static. So we may conclude that static methods cannot be called using instances (only in c#) Why Microsoft has restricted it in C#? Ans: Really there Is no use calling static methods using objects because static methods are stateless. but still Java and C++ latest compilers allow calling static methods using instances. Java sample class Test {      public static void main(String str[])      {            Person p = new Person();            System.out.println(p.GetCount());      } }   class Person {   public static int GetCount()   {      return 100;   } }   Output          100 span.fullpost {display:none;}

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  • Static file download from browser breaking in varnish but works fine in Apache

    - by Ron
    I would at first like to thank everyone at serverfault for this great website and I also come to this site while searching in google for various server related issues and setups. I also have an issue today and so I am posting here and hope that the seniors would help me out. I had setup a website on a dedicated server a few days ago and I used Varnish 3 as the frontend to Apache2 on a Debian Lenny server as the traffic was a bit high. There are several static file downloads of around 10-20 MB in size in the website. The website looked fine in the last few days after I setup. I was checking from a 5mbps + broadband connection and the file downloads were also completed in seconds and working fine. But today I realized that on a slow internet connection the file downloads were breaking off. When I tried to download the files from the website using a browser then it broke off after a minute or so. It kept on happening again and again and so it had nothing to do with the internet connection. The internet connection was around 512 kbps and so it was not dial up level speed too but decent speed where files should easily download though not that fast. Then I thought of trying out with the apache backend port and used the port number to check out if the problem occurs. But then on adding the apache port in the static file download url, the files got downloaded easily and did not break even once. I tried it several times to make sure that it was not a coincidence but every time I was using the apache port in the file download url then it was downloading fine while it was breaking each time with the normal link which was routed through Varnish I suppose. So, it seems Varnish has somehow resulted in the broken file downloads. Could anyone give any idea as to why it is happening and how to fix the problem. For more clarification, take this example: Apache backend set on port 8008, Varnish frontend set on port 80 Now when I download say http://mywebsite.com/directory/filename.extension Then the download breaks off after a minute or so. I cannot be sure it is due to the time or size though and I am just assuming. May be some other reason too. But when I download using: http://mywebsite.com:8008/directory/filename.extension Then the file download does not break at all and it gets download fine. So, it seems that varnish is somehow creating the file download breaking and not apache. Does anybody have any idea as to why it is happening and how can it be fixed. Any help would be highly appreciated. And my varnish default.vcl is backend apache { set backend.host = "127.0.0.1"; set backend.port = "8008"; } sub vcl_deliver { remove resp.http.X-Varnish; remove resp.http.Via; remove resp.http.Age; remove resp.http.Server; remove resp.http.X-Powered-By; }

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  • How does GCC compile applications that reference a static library

    - by technobrat
    I've read that the gcc compiler can perform certain optimization when compiling an application that references a static library, for instance - it will "pull" in only that code from the static library that the application depends upon. This helps keep the size of the application's executable to a minimum if portions of the static library are not being used by the app. 1) Is this true? 2) How does GCC know what code from the static library the application is actually using? Does it only look t the header files that are included (directly and indirectly) in the application and then pull code accordingly? Or does it actually look at what methods from the static library are being called?

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  • Using Static methods or none static methods in Dao Class ?

    - by dankyy1
    Hi I generate Dao classes for some DB operations in this manner making methods of Dao class as static or none static is better? Using sample dao class below ,If more than one client got to use the AddSampleItem method in same time?how this may result? public class SampleDao { static DataAcessor dataAcessor public static void AddSampleItem(object[] params) { dataAcessor =new DataAcessor(); //generate query here string query="..." dataAcessor.ExecuteQery(query); dataAcessor.Close(); } public static void UpdateSampleItem(object[] params) { dataAcessor =new DataAcessor(); //generate query here string query="..." dataAcessor.ExecuteQery(query); dataAcessor.Close(); } }

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  • Java Stop Server Thread

    - by ikurtz
    the following code is server code in my app: private int serverPort; private Thread serverThread = null; public void networkListen(int port){ serverPort = port; if (serverThread == null){ Runnable serverRunnable = new ServerRunnable(); serverThread = new Thread(serverRunnable); serverThread.start(); } else { } } public class ServerRunnable implements Runnable { public void run(){ try { //networkConnected = false; //netMessage = "Listening for Connection"; //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); ServerSocket serverSocket = new ServerSocket(serverPort, backlog); commSocket = serverSocket.accept(); serverSocket.close(); serverSocket = null; //networkConnected = true; //netMessage = "Connected: " + commSocket.getInetAddress().getHostAddress() + ":" + //commSocket.getPort(); //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); } catch (IOException e){ //networkConnected = false; //netMessage = "ServerRunnable Network Unavailable"; //System.out.println(e.getMessage()); //networkMessage = new NetworkMessage(networkConnected, netMessage); //setChanged(); //notifyObservers(networkMessage); } } } The code sort of works i.e. if im attempting a straight connection both ends communicate and update. The issue is while im listening for a connection if i want to quit listening then the server thread continues running and causes problems. i know i should not use .stop() on a thread so i was wondering what the solution would look like with this in mind? EDIT: commented out unneeded code.

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  • Static Class Variables in Dynamic Library and Main Program

    - by Paul
    I am working on a project that has a class 'A' that contains a static stl container class. This class is included in both my main program and a .so file. The class uses the default(implicit, not declared) constructor/destructor. The main program loads the .so file using dlopen() and in its destructor, calls dlclose(). The program crashes after main exits when glibc calls the destructor for the static class member variable. The problem appears to be that when dlclose() is called, the destructor for the static variable is called, then when main exits() glibc also calls the destructor, resulting in a double free. I have 2 questions, namely: 1) In this particular case, why are there not two copies of the static variable(yes i know that sounds somewhat ridiculous, but since both the main program and .so file have a separately compiled 'A', shouldn't they each have one?) 2) Is there any way to resolve this issue without re-writing class 'A' to not contain static member variables?

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  • Thread-local storage segfaults on NetBSD only?

    - by bortzmeyer
    Trying to run a C++ program, I get segmentation faults which appear to be specific to NetBSD. Bert Hubert wrote the simple test program (at the end of this message) and, indeed, it crashes only on NetBSD. % uname -a NetBSD golgoth 5.0.1 NetBSD 5.0.1 (GENERIC) #0: Thu Oct 1 15:46:16 CEST 2009 +stephane@golgoth:/usr/obj/sys/arch/i386/compile/GENERIC i386 % g++ --version g++ (GCC) 4.1.3 20080704 prerelease (NetBSD nb2 20081120) Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. % gdb thread-local-storage-powerdns GNU gdb 6.5 Copyright (C) 2006 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386--netbsdelf"... (gdb) run Starting program: /home/stephane/Programmation/C++/essais/thread-local-storage-powerdns Program received signal SIGSEGV, Segmentation fault. 0x0804881b in main () at thread-local-storage-powerdns.cc:20 20 t_a = new Bogo('a'); (gdb) On other Unix, it works fine. Is there a known issue in NetBSD with C++ thread-local storage? #include <stdio.h> class Bogo { public: explicit Bogo(char a) { d_a = a; } char d_a; }; __thread Bogo* t_a; int main() { t_a = new Bogo('a'); Bogo* b = t_a; printf("%c\n", b->d_a); }

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  • C++/CLI: Compiling static library with /CLR support

    - by user289770
    We have old (working) code that consists of a static library compiled with /CLR, and a C++/CLI DLL that links to the static lib. We are about to add new features to this static lib. Now, I've have heard from numerous sources that CLR static libraries are not supported by Microsoft, and therefore I'm pushing to clean this up and switch to DLL before we start adding new features to this project. However, I haven't been able to find any official information from Microsoft regarding this (say, from MSDN - other than their forums). I will appreciate any resources about this whole "static lib with CLR" issue.

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  • Static and overriding in Java

    - by Abhishek Jain
    public class B { static int i =1; public static int multiply(int a,int b) { return i; } public int multiply1(int a,int b) { return i; } public static void main(String args[]) { B b = new A(); System.out.println(b.multiply(5,2)); System.out.println(b.multiply1(5,2)); } } class A extends B { static int i =8; public static int multiply(int a,int b) { return 5*i; } public int multiply1(int a,int b) { return 5*i; } } Output: 1 40 Why is it so? Please explain.

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  • Return Double from Boost thread

    - by Benedikt Wutzi
    Hi I have an Boost thread which should return a double. The function looks like this: void analyser::findup(const double startwl, const double max, double &myret){ this->data.begin(); for(int i = (int)data.size() ; i >= 0;i--){ if(this->data[i].lambda > startwl){ if(this->data[i].db >= (max-30)) { myret = this->data[i+1].lambda; std::cout <<"in thread " << myret << std::endl; return; } } } } this function is called by another function: void analyser::start_find_up(const double startwl, const double max){ double tmp = -42.0; boost::thread up(&analyser::findup,*this, startwl,max,tmp); std::cout << "before join " << tmp << std::endl; up.join(); std::cout << "after join " << tmp << std::endl; } Anyway I've tried and googled almost anything but i can't get it to return a value. The output looks like this right now. before join -42 in thread 843.487 after join -42 Thanks for any help.

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  • Alternative to c++ static virtual methods

    - by Jaime Pardos
    In C++ is not possible to declare a static virtual function, neither cast a non-static function to a C style function pointer. Now, I have a plain ol' C SDK that uses function pointers heavily. I have to fill a structure with several function pointers. I was planning to use an abstract class with a bunch of static pure virtual methods, and redefine them in derived classes and fill the structure with them. It wasn't until then that I realized that static virtual are not allowed in C++. Is there any good alternative? The best I can think of is defining some pure virtual methods GetFuncA(), GetFuncB(),... and some static members FuncA()/FuncB() in each derived class, which would be returned by the GetFuncX(). Then a function in the abstract class would call those functions to get the pointers and fill the structure.

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  • How to solve JavaScript origin problem with an application and static file server

    - by recipriversexclusion
    In a system that I'm building I want to serve Static files (static HTML pages and a lot of images), and Dynamic XML generated by my servlet. The dynamic XML is generated from my database (through Hibernate) and I use Restlets to serve it in response to API calls. I want to create a static file server (e.g. Apache) so that this does not interfere with the dynamic server traffic. Currently both servers need to run on the same machine. I've never done something like this before and this is where I'm stuck: The static HTML pages contain JavaScript that makes API calls to the dynamic server. However, since the two servers operate on different ports, I get stuck with the same origin problem. How can this be solved? As a bonus, if you can point me to any resources that explain how to create such a static/dynamic content serving system, I'll be happy. Thanks!

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  • Thread-safety of read-only memory access

    - by Edmund
    I've implemented the Barnes-Hut gravity algorithm in C as follows: Build a tree of clustered stars. For each star, traverse the tree and apply the gravitational forces from each applicable node. Update the star velocities and positions. Stage 2 is the most expensive stage, and so is implemented in parallel by dividing the set of stars. E.g. with 1000 stars and 2 threads, I have one thread processing the first 500 stars and the second thread processing the second 500. In practice this works: it speeds the computation by about 30% with two threads on a two-core machine, compared to the non-threaded version. Additionally, it yields the same numerical results as the original non-threaded version. My concern is that the two threads are accessing the same resource (namely, the tree) simultaneously. I have not added any synchronisation to the thread workers, so it's likely they will attempt to read from the same location at some point. Although access to the tree is strictly read-only I am not 100% sure it's safe. It has worked when I've tested it but I know this is no guarantee of correctness! Questions Do I need to make a private copy of the tree for each thread? Even if it is safe, are there performance problems of accessing the same memory from multiple threads?

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  • Create Generic Class Instance from Static Method in a Derived Class

    - by user343547
    I have a class in C# with a template and static method similar to class BClass<T> { public static BClass<T> Create() { return new BClass<T>(); } } From this I derive a class and specify a template parameter to the base class class DClass : BClass<int> { } A problem occurs when I try to use the static method to create an instance of D class Program { static void Main(string[] args) { DClass d = DClass.Create(); } } Gives a compiler error "Cannot implicitly convert type 'Test.BClass<int ' to 'Test.DClass'." Adding the below cast leads to a runtime casting exception. DClass d = (DClass)DClass.Create(); Is there any succint way to allow the static method to create instances of the derived class? Ideally I would like the equivalent of a c++ typedef and I don't want the below syntax (which does work). BClass<int> d = DClass.Create();

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  • Passing variables from a thread to another form using C#

    - by kirstom14
    Hi, I am trying to pass 2 variables from a thread, in the MainForm, to another form, but when doing so an error occurs. private void TrackingThread( ) { float targetX = 0; float targetY = 0; while ( true ) { camera1Acquired.WaitOne( ); camera2Acquired.WaitOne( ); lock ( this ) { // stop the thread if it was signaled if ( ( x1 == -1 ) && ( y1 == -1 ) && ( x2 == -1 ) && ( y2 == -1 ) ) { break; } // get middle point targetX = ( x1 + x2 ) / 2; targetY = ( y1 + y2 ) / 2; } if (directionForm != null) { directionForm.RunMotors(targetX, targetY); } } } In the form, directionForm, I am simply displaying the variables targetX and targetY. The code for the directionForm.RunMotors() is the following: public void RunMotors(float x, float y) { label1.Text = "X-ordinate " + x.ToString(); label2.Text = "Y-ordinate " + y.ToString(); } The error happen when I am trying to display the two variables: "InvalidOperationException was unhandled Cross-threading operation not valid: Control label1 accessed from a thread other than . the thread it was created on" What shall I do??? Thanks in advance

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  • C static variables and intialization

    - by yCalleecharan
    Hi, If I have a global static variable x like in this code #include <stdio.h> #include <stdio.h> static int x; int main(void) { DO SOMETHING WITH x HERE x++; } What will be difference if I opted to initialize x to a value first say as in static int x = 0; before entering "main"? In my first case where I didn't assign a value to x, does the compiler implicitly know that x is to be set to zero as it's a static variable? I heard that we can do this with static variables. Thanks a lot...

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  • C++ design with static methods

    - by user231536
    I would like to define as class X with a static method: class X { static string get_type () {return "X";} //other virtual methods } I would like to force classes which inherit from X to redefine the get_type() method and return strings different from "X" (I am happy if they just redefine get_type for now). How do I do this? I know that I cannot have virtual static methods. Edit: The question is not about the type_id, but in general about a static method that should be overriden. For example class X { static int getid() {return 1;} }

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  • Need a Java based interruptible timer thread

    - by LambeauLeap
    I have a Main Program which is running a script on the target device(smart phone) and in a while loop waiting for stdout messages. However in this particular case, some of the heartbeat messages on the stdout could be spaced almost 45secs to a 1minute apart. something like: stream = device.runProgram(RESTORE_LOGS, new String[] {}); stream.flush(); String line = stream.readLine(); while (line.compareTo("") != 0) { reporter.commentOnJob(jobId, line); line = stream.readLine(); } So, I want to be a able to start a new interruptible thread after reading line from stdout with a required a sleep window. Upon being able to read a new line, I want to be able to interrupt/stop(having trouble killing the process), handle the newline of stdout text and restart a process. And it the event I am not able to read a line within the timer window(say 45secs) I want to a way to get out of my while loop either. I already tried the thread.run, thread.interrupt approach. But having trouble killing and starting a new thread. Is this the best way out or am I missing something obvious?

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