Example for Parallel Programming in Qt

[mounipanditi]

Hi I am a beginner in Qt and while i was browsing about parallel programming in Qt to keep GUI responsive if a task more than normal time i.e 5sec i found this link

https://doc.qt.io/archives/qq/qq27-responsive-guis.html

I need a simple example to understand about Parallel Programming in Qt.
Please help me.

[mrjj]

Hi and welcome
Use the worker approach
https://john.nachtimwald.com/2015/05/02/effective-threading-using-qt/
https://mayaposch.wordpress.com/2011/11/01/how-to-really-truly-use-qthreads-the-full-explanation/

Minimal code. Something like.

class Task : public QObject
{
Q_OBJECT
public:
    Task(){};
    ~Task(){};
public slots:
    void doWork();
signals:
    void workFinished();
};

 QThread* thread = new QThread( );
  Task*    task   = new Task();
  task->moveToThread(thread);
  connect( thread, SIGNAL(started()), task, SLOT(doWork()) );
  connect( task, SIGNAL(workFinished()), thread, SLOT(quit()) );
  //automatically delete thread and task object when work is done:
  connect( thread, SIGNAL(finished()), task, SLOT(deleteLater()) );
  connect( thread, SIGNAL(finished()), thread, SLOT(deleteLater()) );
  thread->start();

void Task::doWork() {
  static int cc = 0;
  while(1) { // ugly
    qDebug() << "alive:" << cc++;
  }
}

Note there is also qtconcurrent
http://doc.qt.io/qt-5/qtconcurrent-runfunction-main-cpp.html

So it depends on what you need. :)

Notice that Qt does not come with beginner documentation on Threads
That you must already know some about.
http://doc.qt.io/qt-5/thread-basics.html

[mounipanditi]

@mrjj

Hi @mrjj thanks for sharing links, i will go through them and i will do my best to understand concepts.