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  • Boost Thread Synchronization

    - by Dave18
    I don't see synchronized output when i comment the the line wait(1) in thread(). can I make them run at the same time (one after another) without having to use 'wait(1)'? #include <boost/thread.hpp> #include <iostream> void wait(int seconds) { boost::this_thread::sleep(boost::posix_time::seconds(seconds)); } boost::mutex mutex; void thread() { for (int i = 0; i < 100; ++i) { wait(1); mutex.lock(); std::cout << "Thread " << boost::this_thread::get_id() << ": " << i << std::endl; mutex.unlock(); } } int main() { boost::thread t1(thread); boost::thread t2(thread); t1.join(); t2.join(); }

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  • Synchronization of Nested Data Structures between Threads in Java

    - by Dominik
    I have a cache implementation like this: class X { private final Map<String, ConcurrentMap<String, String>> structure = new HashMap...(); public String getValue(String context, String id) { // just assume for this example that there will be always an innner map final ConcurrentMap<String, String> innerStructure = structure.get(context); String value = innerStructure.get(id); if(value == null) { synchronized(structure) { // can I be sure, that this inner map will represent the last updated // state from any thread? value = innerStructure.get(id); if(value == null) { value = getValueFromSomeSlowSource(id); innerStructure.put(id, value); } } } return value; } } Is this implementation thread-safe? Can I be sure to get the last updated state from any thread inside the synchronized block? Would this behaviour change if I use a java.util.concurrent.ReentrantLock instead of a synchronized block, like this: ... if(lock.tryLock(3, SECONDS)) { try { value = innerStructure.get(id); if(value == null) { value = getValueFromSomeSlowSource(id); innerStructure.put(id, value); } } finally { lock.unlock(); } } ... I know that final instance members are synchronized between threads, but is this also true for the objects held by these members? Maybe this is a dumb question, but I don't know how to test it to be sure, that it works on every OS and every architecture.

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  • Selenium IDE and Drupal

    Can I use Selenium IDE on a Drupal system? I found http://drupal.org/project/selenium but that involves downloading Core and not using my current machine. Does anybody know of a way to use the IDE with Drupal, or if not what do you suggest I do?

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  • "this" pointer changes in GDB backtrace

    - by Hans
    I am examining a core dump, and noticed that in one frame the 'this' pointer is different than in the next frame (in the same thread). Not just a little different, it went from 0x8167428 to 0x200. I am not that well-versed in using GDB, but this does not seem right to me. Is this problematic, and if so, what could be the cause?

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  • Using Apple autorelease pools without Objective-C

    - by PierreBdR
    I am developing an application that needs to work on Linux, Windows and Mac OS X. To that purpose, I am using C++ with Qt. For many reasons, on Mac OS X, I need to use CoreFoundation functions (such as CFBundleCopyBundleURL) that creates core objects that need to be released with CFRelease. But doing so generate a lots of these warnings: *** __NSAutoreleaseNoPool(): Object 0x224f7e0 of class NSURL autoreleased with no pool in place - just leaking All the code I've seen concerning these autorelease pools are written in Objective-C. Does anybody know how to create/use autorelease pools in C or C++?

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  • Thread implemented as a Singleton

    - by rocknroll
    Hi all, I have a commercial application made with C,C++/Qt on Linux platform. The app collects data from different sensors and displays them on GUI. Each of the protocol for interfacing with sensors is implemented using singleton pattern and threads from Qt QThreads class. All the protocols except one work fine. Each protocol's run function for thread has following structure: void <ProtocolClassName>::run() { while(!mStop) //check whether screen is closed or not { mutex.lock() while(!waitcondition.wait(&mutex,5)) { if(mStop) return; } //Code for receiving and processing incoming data mutex.unlock(); } //end while } Hierarchy of GUI. 1.Login screen. 2. Screen of action. When a user logs in from login screen, we enter the action screen where all data is displayed and all the thread's for different sensors start. They wait on mStop variable in idle time and when data arrives they jump to receiving and processing data. Incoming data for the problem protocol is 117 bytes. In the main GUI threads there are timers which when timeout, grab the running instance of protocol using <ProtocolName>::instance() function Check the update variable of singleton class if its true and display the data. When the data display is done they reset the update variable in singleton class to false. The problematic protocol has the update time of 1 sec, which is also the frame rate of protocol. When I comment out the display function it runs fine. But when display is activated the application hangs consistently after 6-7 hours. I have asked this question on many forums but haven't received any worthwhile suggestions. I Hope that here I will get some help. Also, I have read a lot of literature on Singleton, multithreading, and found that people always discourage the use of singletons especially in C++. But in my application I can think of no other design for implementation. Thanks in advance A Hapless programmer

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  • Lightweight spinlocks built from GCC atomic operations?

    - by Thomas
    I'd like to minimize synchronization and write lock-free code when possible in a project of mine. When absolutely necessary I'd love to substitute light-weight spinlocks built from atomic operations for pthread and win32 mutex locks. My understanding is that these are system calls underneath and could cause a context switch (which may be unnecessary for very quick critical sections where simply spinning a few times would be preferable). The atomic operations I'm referring to are well documented here: http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Atomic-Builtins.html Here is an example to illustrate what I'm talking about. Imagine a RB-tree with multiple readers and writers possible. RBTree::exists() is read-only and thread safe, RBTree::insert() would require exclusive access by a single writer (and no readers) to be safe. Some code: class IntSetTest { private: unsigned short lock; RBTree<int>* myset; public: // ... void add_number(int n) { // Aquire once locked==false (atomic) while (__sync_bool_compare_and_swap(&lock, 0, 0xffff) == false); // Perform a thread-unsafe operation on the set myset->insert(n); // Unlock (atomic) __sync_bool_compare_and_swap(&lock, 0xffff, 0); } bool check_number(int n) { // Increment once the lock is below 0xffff u16 savedlock = lock; while (savedlock == 0xffff || __sync_bool_compare_and_swap(&lock, savedlock, savedlock+1) == false) savedlock = lock; // Perform read-only operation bool exists = tree->exists(n); // Decrement savedlock = lock; while (__sync_bool_compare_and_swap(&lock, savedlock, savedlock-1) == false) savedlock = lock; return exists; } }; (lets assume it need not be exception-safe) Is this code indeed thread-safe? Are there any pros/cons to this idea? Any advice? Is the use of spinlocks like this a bad idea if the threads are not truly concurrent? Thanks in advance. ;)

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  • Avahi DNS Stack for iPhone?

    - by sneha
    Hello, I would like to know if we have an avahi api for iphone side? Alternatively, can we implement avahi protocol in iphone? The avahi API provides: avahi-core: an API for embedding a complete mDNS/DNS-SD stack into your software. This is intended for developers of embedded appliances only. We dissuade from using this API in normal desktop applications since it is not a good idea to run multiple mDNS stacks simultaneously on the same host.

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  • Any porting avaiable of backtrace for uclibc?

    - by user303967
    We are running the uclibc linux on ARM 9. The problem is uclibc doesn't support backtrace. When core-dump happen, cannot grap the call stack. Anyone has good solution on that? For example, an existing porting of backtrace for uclibc? or any good method to grap call stack when call dump happen(uclibc+ARM+Linux)? thanks

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  • Running virtual machines: Linux vs Windows 7

    - by vikp
    Hi, I have tried running windows xp development virtual machine under windows 7 and the performance was dreadful. I'm considering installing Linux and running the virtual machine from the Linux, but I'm not sure whether I can expect any performance gains? It's a 2.4ghz core 2 duo machine with 4gb ram and 5400 rpm hdd. Can somebody please recommend very cut down version of linux that can run VMWare player and isn't resource hungry? Thank you

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  • run jsf application with myeclipse and jboss server

    - by chetan
    I develop simple jsf login application,that use icefaces component but, when I tries to run it in jboss server I got following error. Can't find TLD for location [http://java.sun.com/jsf/core]. JAR containing the TLD may not be in the classpath Can't find TLD for location [http://java.sun.com/jsf/html]. JAR containing the TLD may not be in the classpath

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  • Are Drupal theme settings cached?

    - by barraponto
    i want to change theme_username, a core theme function that outputs that dreadful "not verified" string on users who are not logged in (when they comment, for example). i want a checkbox in admin/build/themes/settings/MYTHEME to change that. but since that theme function gets called a lot, will it hurt the performance of any site using my theme or are theme settings cached?

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  • How to create JPA EntityMananger in Spring Context?

    - by HDave
    I have a JPA/Spring application that uses Hibernate as the JPA provider. In one portion of the code, I have to manually create a DAO in my application with the new operator rather than use Spring DI. When I do this, the @PersistenceContext annotation is not processed by Spring. In my code where I create the DAO I have an EntityManagerFactory which I used to set the entityManager as follows: @PersistenceUnit private EntityManagerFactory entityManagerFactory; MyDAO dao = new MyDAOImpl(); dao.setEntityManager(entityManagerFactory.createEntityManager()); The problem is that when I do this, I get a Hibernate error: Could not find UserTransaction in JNDI [java:comp/UserTransaction] It's as if the HibernateEntityManager never received all the settings I've configured in Spring: <bean id="myAppTestLocalEmf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="persistenceUnitName" value="myapp-core" /> <property name="persistenceUnitPostProcessors"> <bean class="com.myapp.core.persist.util.JtaPersistenceUnitPostProcessor"> <property name="jtaDataSource" ref="myappPersistTestJdbcDataSource" /> </bean> </property> <property name="jpaProperties"> <props> <prop key="hibernate.transaction.factory_class">org.hibernate.transaction.JTATransactionFactory</prop> <prop key="hibernate.transaction.manager_lookup_class">com.atomikos.icatch.jta.hibernate3.TransactionManagerLookup</prop> </props> </property> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <property name="showSql" value="true" /> <!-- The following use the PropertyPlaceholderConfigurer but it doesn't work in Eclipse --> <property name="database" value="$DS{hibernate.database}" /> <property name="databasePlatform" value="$DS{hibernate.dialect}" /> I am not sure, but I think the issue might be that I am not creating the entity manager correctly with the plain vanilla createEntityManager() call rather than passing in a map of properties. I say this because when Spring's LocalContainerEntityManagerFactoryBean proxy's the call to Hibernate's createEntityManager() all of the Spring configured options are missing. That is, there is no Map argument to the createEntityManager() call. Perhaps it is another problem entirely however....not sure!

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  • Error after installing Django (supposed PATH or PYTHONPATH "error")

    - by illuminated
    Hi all, I guess this is a PATH/PYTHONPATH error, but my attempts failed so far to make django working. System is Ubuntu 10.04, 64bit: mx:~/webapps$ cat /etc/lsb-release DISTRIB_ID=Ubuntu DISTRIB_RELEASE=10.04 DISTRIB_CODENAME=lucid DISTRIB_DESCRIPTION="Ubuntu 10.04 LTS" Python version: 2.6.5: @mx:~/webapps$ python -V Python 2.6.5 When I run django-admin.py, the following happens: mx:~/webapps$ django-admin.py Traceback (most recent call last): File "/usr/local/bin/django-admin.py", line 2, in <module> from django.core import management ImportError: No module named django.core Similar when I import django in python shell: mx:~/webapps$ python Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import django Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: No module named django >>> quit() More details: mx:~/webapps$ python -c "from distutils.sysconfig import get_python_lib; print get_python_lib()" /usr/lib/python2.6/dist-packages Within python shell: Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import sys >>> print sys.path ['', '/usr/lib/python2.6/dist-packages/django', '/usr/local/lib/python2.6/dist-packages/django/bin', '/usr/local/lib/python2.6/dist-packages/django', '/home/petra/webapps', '/usr/lib/python2.6', '/usr/lib/python2.6/plat-linux2', '/usr/lib/python2.6/lib-tk', '/usr/lib/python2.6/lib-old', '/usr/lib/python2.6/lib-dynload', '/usr/lib/python2.6/dist-packages', '/usr/lib/python2.6/dist-packages/PIL', '/usr/lib/pymodules/python2.6'] django-admin.py can be found here: mx:~/webapps$ locate django-admin.py ~/install/sources/Django-1.2.1/build/lib.linux-i686-2.6/django/bin/django-admin.py ~/install/sources/Django-1.2.1/build/scripts-2.6/django-admin.py ~/install/sources/Django-1.2.1/django/bin/django-admin.py /usr/local/bin/django-admin.py /usr/local/lib/python2.6/dist-packages/django/bin/django-admin.py /usr/local/lib/python2.6/dist-packages/django/bin/django-admin.pyc and in the end this doesn't help: export PYTHONPATH="/usr/lib/python2.6/dist-packages/django:$PYTHONPATH" nor this: export PYTHONPATH="/usr/local/lib/python2.6/dist-packages/django:$PYTHONPATH" How to solve this !? Thanks all in advance! :)

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  • Touch event in CPLayerHostingView?

    - by senthilmuthu
    Hi, i am using Core-plot . but when i declare the normal UIView as CPLayerHostingView,how can i handle drawRect of that view , i cant give another custom UIview name and write code in drawRect of that view?please any help to handle drawRect of CPLayerHostingView?

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  • How to properly implement cheat codes?

    - by Axarydax
    Hi, what would be the best way to implement kind of cheat codes in general? I have WinForms application in mind, where a cheat code would unlock an easter egg, but the implementation details are not relevant. The best approach that comes to my mind is to keep index for each code - let's consider famous DOOM codes - IDDQD and IDKFA, in a fictional C# app. string[] CheatCodes = { "IDDQD", "IDKFA"}; int[] CheatIndexes = { 0, 0 }; const int CHEAT_COUNT = 2; void KeyPress(char c) { for (int i = 0; i < CHEAT_COUNT; i++) //for each cheat code { if (CheatCodes[i][CheatIndexes[i]] == c) { //we have hit the next key in sequence if (++CheatIndexes[i] == CheatCodes[i].Length) //are we in the end? { //Do cheat work MessageBox.Show(CheatCodes[i]); //reset cheat index so we can enter it next time CheatIndexes[i] = 0; } } else //mistyped, reset cheat index CheatIndexes[i] = 0; } } Is this the right way to do it?

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  • Netbeans CVS - existing repo - existing working copy

    - by ExTexan
    I'm using Netbeans to develop with Drupal. I'm trying to let Netbeans get drupal core and modules from the repository on drupal.org to my local working copy. Problem is: I already have a working copy that is not versioned yet. When I try to checkout a copy from drupal.org, Netbeans asks if I want to create a new project - I don't. How can I turn my local copy into a "checked out" working copy?

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  • How can I build multiple processes with TBB?

    - by Jackie
    Now I plan to parallelize my sequential solver. I hope I could run several copies of my solver(maybe with different parameters) in parallel simultaneously on a multi-core computer. can I do this with TBB? The reason I ask this question is that the book says: do not introduce anything in your code that will not allow single-thread execution. Any experts can explain this issue? Thanks.

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  • What is common architecture of notification system on the web-forum, PMB and etc.?

    - by glaz666
    What I need is - list of new stuff from last visit - when user has already checked out some new entity since his last visit (ex. post on forum), mark this entity as read in the list - count different types of entities - private messages, posts, comments and etc. There are lot of websites using this technique for private messaging, listing new stuff and etc (ex. phpBB, this one and etc). Are there any common pattern, description of the system core which will events, making lists?

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