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  • Ref to map vs. map to refs vs. multiple refs

    - by mikera
    I'm working on a GUI application in Swing+Clojure that requires various mutable pieces of data (e.g. scroll position, user data, filename, selected tool options etc.). I can see at least three different ways of handling this set of data: Create a ref to a map of all the data: (def data (ref { :filename "filename.xml" :scroll [0 0] })) Create a map of refs to the individual data elements: (def datamap { :filename (ref "filename.xml") :scroll (ref [0 0]) })) Create a separate ref for each in the namespace: (def scroll (ref [0 0])) (def filename (ref "filename.xml")) Note: This data will be accessed concurrently, e.g. by background processing threads or the Swing event handling thread. However there probably isn't a need for consistent transactional updates of multiple elements. What would be your recommended approach and why?

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  • My C# program running as Windows Service is blocking Windows XP from hibernation

    - by sherpa
    I have Windows Service written in C#. It starts two threads, one is pooling a Web Service, second is waiting on a Monitor object for a new job to arrive. Besides that, the main thread acts as a WCF service host using NetNamedPipeBinding. It lets the client application to register a callback and then sends notifications back. The problem I have is that when this Windows Service is running, I cannot hibernate or Standby my computer which is running on Windows XP, SP3. When I set Windows to hibernate or standby, nothing happens. Then, at the moment when I go to Service Manager and stop the service, the system hibernation starts immediately. The service class extending the ServiceBase has properties like CanHandlePowerEvent, CanPauseAndContinue, etc. set to true... That didn't make any difference. The question is: what can be blocking the Hibernation/Standby from proceeding? What should I take care about to avoid it?

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  • Implicit Memory Barriers

    - by foo
    let's say i have variables A, B and C that two threads (T1, T2) share. i have the following code: //T1 //~~ A = 1; B = 1; C = 1; InterlockedExchange(ref Foo, 1); //T2 (executes AFTER T1 calls InterlockedExchange) //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ InterlockedExchange(ref Bar, 1); WriteLine(A); WriteLine(B); WriteLine(C); Question: does calling InterlockedExchange (implicit full fence) on T1 and T2, gurentess that T2 will "See" the write done by T1 before the fence? (A, B and C variables), even though those variables are not plance on the same cache-line as Foo and Bar?

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  • Does my Dictionary must use locking mechanism?

    - by theateist
    Many threads have access to summary. Each thread will have an unique key for accessing the dictionary; Dictionary<string, List<Result>> summary; Do I need locking for following operations? summary[key] = new List<Result>() summary[key].Add(new Result()); It seems that I don't need locking because each thread will access dictionary with different key, but won't the (1) be problematic because of adding concurrently new record to dictionary with other treads?

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  • Android Multithreading, creating new thread not executing rest of OnCreate

    - by Aidan
    Hi Guys, Basically I'm trying to run 2 threads within the same class at the same time. The code runs but only executes whats in run() and doesnt finish the onCreate method... anyone know why? public Camera1(){ t = new Thread(this, "My Thread"); t.start(); } public void run(){ bearing(); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); new Camera1(); makeview(); tracking(); } Thanks!

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  • While using ConcurrentQueue, trying to dequeue while looping through in parallel

    - by James Black
    I am using the parallel data structures in my .NET 4 application and I have a ConcurrentQueue that gets added to while I am processing through it. I want to do something like: personqueue.AsParallel().WithDegreeOfParallelism(20).ForAll(i => ... ); as I make database calls to save the data, so I am limiting the number of concurrent threads. But, I expect that the ForAll isn't going to dequeue, and I am concerned about just doing ForAll(i => { personqueue.personqueue.TryDequeue(...); ... }); as there is no guarantee that I am popping off the correct one. So, how can I iterate through the collection and dequeue, in a parallel fashion. Or, would it be better to use PLINQ to do this processing, in parallel?

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  • zeromq installtion on mac os snow leopard

    - by Ashish
    I have installed zeromq 2.1.11 on mac os x using the steps given on http://www.zeromq.org/area:download Then i installed pyzmq (python bindings ) But i get the following error : import zmq Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> import zmq File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/zmq/__init__.py", line 35, in <module> from zmq.utils import initthreads # initialize threads ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/zmq/utils/initthreads.so, 2): no suitable image found. Did find: /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/zmq/utils/initthreads.so: no matching architecture in universal wrapper

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  • Performance characteristics of pthreads vs ucontext

    - by Robert Mason
    I'm trying to port a library that uses ucontext over to a platform which supports pthreads but not ucontext. The code is pretty well written so it should be relatively easy to replace all the calls to the ucontext API with a call to pthread routines. However, does this introduce a significant amount of additional overhead? Or is this a satisfactory replacement. I'm not sure how ucontext maps to operating system threads, and the purpose of this facility is to make coroutine spawning fairly cheap and easy. So, question is: Does replacing ucontext calls with pthread calls significantly change the performance characteristics of a library?

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  • Optimizing BeautifulSoup (Python) code

    - by user283405
    I have code that uses the BeautifulSoup library for parsing, but it is very slow. The code is written in such a way that threads cannot be used. Can anyone help me with this? I am using BeautifulSoup for parsing and than save into a DB. If I comment out the save statement, it still takes a long time, so there is no problem with the database. def parse(self,text): soup = BeautifulSoup(text) arr = soup.findAll('tbody') for i in range(0,len(arr)-1): data=Data() soup2 = BeautifulSoup(str(arr[i])) arr2 = soup2.findAll('td') c=0 for j in arr2: if str(j).find("<a href=") > 0: data.sourceURL = self.getAttributeValue(str(j),'<a href="') else: if c == 2: data.Hits=j.renderContents() #and few others... c = c+1 data.save() Any suggestions? Note: I already ask this question here but that was closed due to incomplete information.

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  • custom progress bar in net compact framework

    - by amolitrivedi
    Hi all, I want to have my own progress bar in .net compact framework, instead of default wait cursor. I have tried with a form, having only a progress bar, and showing and hiding the form when I want to show some background activity running, but that does not update the progress bar. I have found out that it needs to be on different thread. I am quite weak at threads, I cant get it working. Please help me out. Thanks in advance.

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

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

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  • Downloading HTTP URLs asynchronously in C++

    - by Joey Adams
    What's a good way to download HTTP URLs (e.g. such as http://0.0.0.0/foo.htm ) in C++ on Linux ? I strongly prefer something asynchronous. My program will have an event loop that repeatedly initiates multiple (very small) downloads and acts on them when they finish (either by polling or being notified somehow). I would rather not have to spawn multiple threads/processes to accomplish this. That shouldn't be necessary. Should I look into libraries like libcurl? I suppose I could implement it manually with non-blocking TCP sockets and select() calls, but that would likely be less convenient.

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  • Are memory barriers necessary for atomic reference counting shared immutable data?

    - by Dietrich Epp
    I have some immutable data structures that I would like to manage using reference counts, sharing them across threads on an SMP system. Here's what the release code looks like: void avocado_release(struct avocado *p) { if (atomic_dec(p->refcount) == 0) { free(p->pit); free(p->juicy_innards); free(p); } } Does atomic_dec need a memory barrier in it? If so, what kind of memory barrier? Additional notes: The application must run on PowerPC and x86, so any processor-specific information is welcomed. I already know about the GCC atomic builtins. As for immutability, the refcount is the only field that changes over the duration of the object.

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  • Regular expression help parsing SQLIO output

    - by jaspernygaard
    Hi I've been working on a regular expression to parse the output of a series of SQLIO runs. I've gotten pretty far, but not quite there yet. I'm seeking a 100% regex solution and no pre-manipulation of the input. Could anyone assist with a little guidance with the following regular expression: .*v(?<SQLIOVersion>\d\.\d).*\n.*\n(?<threads>\d*)\s.*for\s(?<Seconds>\d+).*\n.*using\s(?<clustersize>[0-9]*)KB.*\n.*\n.*size:\s(?<currentfilesize>\d+).*\n.*\n.*\n.*\n.*\s(?<IOs>\d*\.\d*).*\n.*\s(?<MBs>\d*\.\d*).*\n.*\n.*\s(?<MinLatency_ms>\d+).*\n.*\s(?<AvgLatency_ms>\d+).*\n.*\s(?<MaxLatency_ms>\d+).*\n.*\n.*\n\%\:..(?<ms>\d*\s+)* Here's a snippet of the output - note the headers, which change during the SQLIO batch run: File

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  • Qt C++ signals and slots did not fire

    - by Xegara
    I have programmed Qt a couple of times already and I really like the signals and slots feature. But now, I guess I'm having a problem when a signal is emitted from one thread, the corresponding slot from another thread is not fired. The connection was made in the main program. This is also my first time to use Qt for ROS which uses CMake. The signal fired by the QThread triggered their corresponding slots but the emitted signal of my class UserInput did not trigger the slot in tflistener where it supposed to. I have tried everything I can. Any help? The code is provided below. Main.cpp #include <QCoreApplication> #include <QThread> #include "userinput.h" #include "tfcompleter.h" int main(int argc, char** argv) { QCoreApplication app(argc, argv); QThread *thread1 = new QThread(); QThread *thread2 = new QThread(); UserInput *input1 = new UserInput(); TfCompleter *completer = new TfCompleter(); QObject::connect(input1, SIGNAL(togglePause2()), completer, SLOT(toggle())); QObject::connect(thread1, SIGNAL(started()), completer, SLOT(startCounting())); QObject::connect(thread2, SIGNAL(started()), input1, SLOT(start())); completer->moveToThread(thread1); input1->moveToThread(thread2); thread1->start(); thread2->start(); app.exec(); return 0; } What I want to do is.. There are two seperate threads. One thread is for the user input. When the user enters [space], the thread emits a signal to toggle the boolean member field of the other thread. The other thread 's task is to just continue its process if the user wants it to run, otherwise, the user does not want it to run. I wanted to grant the user to toggle the processing anytime that he wants, that's why I decided to bring them into seperate threads. The following codes are the tflistener and userinput. tfcompleter.h #ifndef TFCOMPLETER_H #define TFCOMPLETER_H #include <QObject> #include <QtCore> class TfCompleter : public QObject { Q_OBJECT private: bool isCount; public Q_SLOTS: void toggle(); void startCounting(); }; #endif tflistener.cpp #include "tfcompleter.h" #include <iostream> void TfCompleter::startCounting() { static uint i = 0; while(true) { if(isCount) std::cout << i++ << std::endl; } } void TfCompleter::toggle() { // isCount = ~isCount; std::cout << "isCount " << std::endl; } UserInput.h #ifndef USERINPUT_H #define USERINPUT_H #include <QObject> #include <QtCore> class UserInput : public QObject { Q_OBJECT public Q_SLOTS: void start(); // Waits for the keypress from the user and emits the corresponding signal. public: Q_SIGNALS: void togglePause2(); }; #endif UserInput.cpp #include "userinput.h" #include <iostream> #include <cstdio> // Implementation of getch #include <termios.h> #include <unistd.h> /* reads from keypress, doesn't echo */ int getch(void) { struct termios oldattr, newattr; int ch; tcgetattr( STDIN_FILENO, &oldattr ); newattr = oldattr; newattr.c_lflag &= ~( ICANON | ECHO ); tcsetattr( STDIN_FILENO, TCSANOW, &newattr ); ch = getchar(); tcsetattr( STDIN_FILENO, TCSANOW, &oldattr ); return ch; } void UserInput::start() { char c = 0; while (true) { c = getch(); if (c == ' ') { Q_EMIT togglePause2(); std::cout << "SPACE" << std::endl; } c = 0; } } Here is the CMakeLists.txt. I just placed it here also since I don't know maybe the CMake has also a factor here. CMakeLists.txt ############################################################################## # CMake ############################################################################## cmake_minimum_required(VERSION 2.4.6) ############################################################################## # Ros Initialisation ############################################################################## include($ENV{ROS_ROOT}/core/rosbuild/rosbuild.cmake) rosbuild_init() set(CMAKE_AUTOMOC ON) #set the default path for built executables to the "bin" directory set(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/bin) #set the default path for built libraries to the "lib" directory set(LIBRARY_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/lib) # Set the build type. Options are: # Coverage : w/ debug symbols, w/o optimization, w/ code-coverage # Debug : w/ debug symbols, w/o optimization # Release : w/o debug symbols, w/ optimization # RelWithDebInfo : w/ debug symbols, w/ optimization # MinSizeRel : w/o debug symbols, w/ optimization, stripped binaries #set(ROS_BUILD_TYPE Debug) ############################################################################## # Qt Environment ############################################################################## # Could use this, but qt-ros would need an updated deb, instead we'll move to catkin # rosbuild_include(qt_build qt-ros) rosbuild_find_ros_package(qt_build) include(${qt_build_PACKAGE_PATH}/qt-ros.cmake) rosbuild_prepare_qt4(QtCore) # Add the appropriate components to the component list here ADD_DEFINITIONS(-DQT_NO_KEYWORDS) ############################################################################## # Sections ############################################################################## #file(GLOB QT_FORMS RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} ui/*.ui) #file(GLOB QT_RESOURCES RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} resources/*.qrc) file(GLOB_RECURSE QT_MOC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} FOLLOW_SYMLINKS include/rgbdslam_client/*.hpp) #QT4_ADD_RESOURCES(QT_RESOURCES_CPP ${QT_RESOURCES}) #QT4_WRAP_UI(QT_FORMS_HPP ${QT_FORMS}) QT4_WRAP_CPP(QT_MOC_HPP ${QT_MOC}) ############################################################################## # Sources ############################################################################## file(GLOB_RECURSE QT_SOURCES RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} FOLLOW_SYMLINKS src/*.cpp) ############################################################################## # Binaries ############################################################################## rosbuild_add_executable(rgbdslam_client ${QT_SOURCES} ${QT_MOC_HPP}) #rosbuild_add_executable(rgbdslam_client ${QT_SOURCES} ${QT_RESOURCES_CPP} ${QT_FORMS_HPP} ${QT_MOC_HPP}) target_link_libraries(rgbdslam_client ${QT_LIBRARIES})

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  • Encoding with url and api

    - by user2950824
    So I have this web app set up and running and it works fine for any username that you request, but when i try http://mrcastelo.pythonanywhere.com/lol/euw/Nazaré, it simply doesnt work - the error that I get on the server is the following: iddata= getJSON(urllolbase+region+urlid+username) #SummonerID UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 5: ordinal not in range(128) It is annoying me greatly, I've tried some other threads but none of them came to a fix. The api that I am using (www.legendaryapi.com) does accept this because this works. Any idea on how to fix this?

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  • which layout engine for finding coordinates of html elements on the web page?

    - by Mexx
    I am doing some web data classification task and was thinking if I could get the co-ordinates of html elements as they would appear on a web-browser without taking into consideration any css or javascript being referred in the web page. My language of programming is c++ and the need results for a couple million of pages, so it has to be fast. I know there is a Microsoft COM component which renders the page in a web browser control and then can be queried for position of different html tags. But this is not suitable in my case as it first renders the whole page which takes up a lot of time. So as I found out, there are open-source layout engines WebKit, Gecko that can probably be used for this. But that's a huge piece of code and I need someone to direct me to the right classes or right modules to look into or any previous/similar work someone has done previously. Also, please let me know what you guys think is a good choice if I want to customize the existing code for use with multiple threads to make it faster. Thanks

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  • How to handle all unhandled exceptions when using Task Parallel Library?

    - by Buu Nguyen
    I'm using the TPL (Task Parallel Library) in .NET 4.0. I want to be able to centralize the handling logic of all unhandled exceptions by using the Thread.GetDomain().UnhandledException event. However, in my application, the event is never fired for threads started with TPL code, e.g. Task.Factory.StartNew(...). The event is indeed fired if I use something like new Thread(threadStart).Start(). This MSDN article suggests to use Task#Wait() to catch the AggregateException when working with TPL, but that is not I want because it is not "centralized" enough a mechanism. Does anyone experience same problem at all or is it just me? Do you have any solution for this?

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  • problem with HttpWebRequest.GetResponse perfomance in multithread applcation

    - by Nikita
    I have very bad perfomance of HttpWebRequest.GetResponse method when it is called from different thread for different URLs. For example if we have one thread and execute url1 it requires 3sec. If we ececute url1 and url2 in parallet it requires 10sec, first request ended after 8sec and second after 10sec. If we exutet 10 URLs url1, url2, ... url0 it requires 1min 4 sec!!! first request ended after 50 secs! I use GetResponse method. I tried te set DefaultConnectionLimit but it doesn't help. If use BeginGetRequest/EndGetResponse methods it works very fast but only if this methods called from one thread. If from different it is also very slowly. I need to execute Http requests from many threads at one time. ?an anyone ever encountered such a problem? Thank you for any suggestions.

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  • Why doesn't Perl threading work when I call readdir beforehand?

    - by Kevin
    Whenever I call readdir before I create a thread, I get an error that looks like this: perl(2820,0x7fff70c33ca0) malloc: * error for object 0x10082e600: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug Abort trap What's strange is that it happens when I call readdir before I create a thread (i.e. readdir is not called in any concurrent code). I don't even use the results from readdir, just making the call to it seems to screw things up. When I get rid of it, things seem to work fine. Some example code is below: opendir(DIR, $someDir); my @allFiles = readdir(DIR); close(DIR); my $thread = threads-create(\&sub1); $thread-join(); sub sub1 { print "in thread\n" }

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  • Cilk or Cilk++ or OpenMP

    - by Aman Deep Gautam
    I'm creating a multi-threaded application in Linux. here is the scenario: Suppose I am having x instance of a class BloomFilter and I have some y GB of data(greater than memory available). I need to test membership for this y GB of data in each of the bloom filter instance. It is pretty much clear that parallel programming will help to speed up the task moreover since I am only reading the data so it can be shared across all processes or threads. Now I am confused about which one to use Cilk, Cilk++ or OpenMP(which one is better). Also I am confused about which one to go for Multithreading or Multiprocessing

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  • Handling Incoming Data from Multiple Sockets in Python

    - by user859434
    Background: I have a current implementation that receives data from about 120 different socket connections in python. In my current implementation, I handle each of these separate socket connections with a dedicated thread for each. Each of these threads parse the data and eventually store it within a shared locked dictionary. These sockets DO NOT have uniform data rates, some sockets get more data than others. Question: Is this the best way to handle incoming data in python, or does python have a better way on handling multiple sockets per thread?

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  • Can in-memory SQLite databases be used concurrently?

    - by Kent Boogaart
    In order to prevent a SQLite in-memory database from being cleaned up, one must use the same connection to access the database. However, using the same connection causes SQLite to synchronize access to the database. Thus, if I have many threads performing reads against an in-memory database, it is slower on a multi-core machine than the exact same code running against a file-backed database. Is there any way to get the best of both worlds? That is, an in-memory database that permits multiple, concurrent calls to the database?

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  • how to selfhost wcf without iis

    - by dotnetcoder
    Reading up on WCF we have self hosting option available , one limitation here is we have to manage the host process lifecycle ourselves. What I am exploring here is to run the service without IIS and do a self hosting. Few things come to mind - How will request management work here. In case of IIS it manages the request and give control to dotnet on a particular thread. In absence of IIS do we need to write code ourselves to manage incoming requests ( say on a tcp port ) or WCF provides some classes to manage request and spawn threads to process each thread. I am aware that in case of self hosting this needs to be a windows service. In case of self hosting how can me tap on the number of simultaneous requests on the sever , it can be managed by limiting the thread pool ? or we can configure this via wcf ? Thanks dc

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  • Play bitmap animation list in reverse order?

    - by Ixx
    I have a bitmap animation defined in XML, to open a door. I also need to animate closing the door, which contains the same frames but in reverse order. I don't want to create a second XML for this. The only reverse parameter I found in the documentation is related with repeating, and this doesn't apply, since I want the opening animation to finish when the door is closed and not continue to closing animation. I also found some threads about using a custom interpolator, but can I use / makes sense with a bitmap animation? How can I play the XML animation in reverse order?

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