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QFutureWatcher - timing issue

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  • Pl45m4P Pl45m4

    @AnneRanch said in QFutureWatcher - timing issue:

    I am already setting some defaults to real values

    What defaults? The connection, I've shown above and which is used in your example, sets up the QProgressDialog according to your QFutureWatchers "watched" work.

    progressRangeChanged(int,int) will set the range (0% - 100%) to (0, 10), where 10 = 100%. So each iteration (total of 10) equals 10%.
    Every time one iteration is done (one iteration = count from 0 to 1000*1000*40), progressValueChanged(int) is emitted and sets the corresponding percentage in your QProgressDialog.
    Then, in the end, waitForFinished() is called to "block" the main thread until all future work has been done (and to ensure that you have all results from all threads, when reaching this point in your code).

    Probably your QElapsedTimer causes the issue, because it traps your thread in your do - while loop.

    A Offline
    A Offline
    Anonymous_Banned275
    wrote on last edited by
    #5

    OK, I admit I have a basic misunderstanding of the "connections" between parts of the code.
    I need 10 second delay , I picked 10 iterations of 1 second time delay monitoring elapsed time instead of using magic numbers to eat CPU.
    ( if there is a better way to do that please make a suggestion how.)

    I have NOT changed any of the "connect" functions.

    The progress of the delay is displayed in modal

    QProgressDialog dialog ( "TEST window title ",
    " BUTTON text", 0, iterations ,0 ,0);

    run as

    dialog.exec();

    The dialog shows progress of 10 % and then jumps to 50% and closes.

    I monitor the entire time of the dialog.exec(); and it reads approximately 3 seconds.

    Apparently I need to figure out HOW to actually read the futurewatcher SINGAL to find out WHY the values are not as expected AND where are they coming form.

    I am not sure if I can read the values while running dialog.exec(); AKA how to access current values of interest.

    I

    1 Reply Last reply
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    • A Anonymous_Banned275

      @Pl45m4 said in QFutureWatcher - timing issue:

      @AnneRanch

      You are still referring to / using this example, right? (https://www.bogotobogo.com/Qt/Qt5_QtConcurrent_QFutureWatcher_QProgressDialog_map.php)

      How is your "work" task configured? How do you stop your task (when do you call waitForFinished?)

      If I set # of iterations to 200 - is see percentage 1,2,3, etc up to 100 BUT it never runs thru ALL 200 iterations.

      This looks like a wrong configuration

      If you are using the example code (at least parts of it), then this

      connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)), &dialog, SLOT(setRange(int,int)));
      connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));
      

      should take care of your process dialog and its correct setup (set a range matching your total work and a correct update interval).

      Found the problem, but not the solution, not yet.
      From get go I was not too happy with the tutorial which "comments " the C code in style:

      int a = 10 // set variable a to 10

      The problem is in constructing the QProgressDialog using default constrictor. I am already setting some defaults to real values , but it is not enough.
      I'll be replacing the tutorial default QProgressDialog with my own next.

      Pablo J. RoginaP Offline
      Pablo J. RoginaP Offline
      Pablo J. Rogina
      wrote on last edited by
      #6

      @AnneRanch said in QFutureWatcher - timing issue:

      default constrictor

      Are you coding in Python?

      PS: sorry but I couldn't resist...

      Upvote the answer(s) that helped you solve the issue
      Use "Topic Tools" button to mark your post as Solved
      Add screenshots via postimage.org
      Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

      A 1 Reply Last reply
      4
      • Pablo J. RoginaP Pablo J. Rogina

        @AnneRanch said in QFutureWatcher - timing issue:

        default constrictor

        Are you coding in Python?

        PS: sorry but I couldn't resist...

        A Offline
        A Offline
        Anonymous_Banned275
        wrote on last edited by
        #7

        @Pablo-J-Rogina said in QFutureWatcher - timing issue:

        @AnneRanch said in QFutureWatcher - timing issue:

        default constrictor

        Are you coding in Python?

        PS: sorry but I couldn't resist...

        I am about to start coding in machine language...
        This Qt stuff with its defaults / inheritance etc. is driving me nuts.

        'BTW the "constrictor" I used does not do simple window title as advertised.
        Wonder what other parameters passed to it do not work...

        1 Reply Last reply
        0
        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #8

          Hi,

          Please show the code you are currently using. That will help us better understand what happens to you.

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

          A 1 Reply Last reply
          0
          • SGaistS SGaist

            Hi,

            Please show the code you are currently using. That will help us better understand what happens to you.

            A Offline
            A Offline
            Anonymous_Banned275
            wrote on last edited by
            #9

            @SGaist said in QFutureWatcher - timing issue:

            Hi,

            Please show the code you are currently using. That will help us better understand what happens to you.

            Are you positive ?
            My code is currently more debug lines than code and from past experience I am reluctant to post it . I do not need my coding style criticized by Peanut gallery .

            In the mean time
            I think my issue is in interaction of QProgressDialog changing "the value" , and actually understanding` what is the value. I though it is the percentage of completion of the QProgressDialog "progress bar" related to # of iterations, but I may be wrong.

               QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)), &dialog, SLOT(setRange(int,int)));
                QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));
            
                // Start the computation.
                qDebug()<<" Start the computation - ";
                qDebug()<< "apply delay function "spin"  to each vector";
            
                futureWatcher.setFuture(QtConcurrent::map(vector, spin));
            
             //  futureWatcher.setFuture();
            
                // Display the dialog and start the event loop.
                qDebug()<<" RUN dialog.exec() Display the dialog and start the dialog event loop";
            
                //   dialog.setMaximum(50);
                // dialog.setRange(10, 50 );
            
                qDebug()<<" START dialog.exec() " ; // ? << dialog.setRange(10,30);
                // progress dialog event loop
                //dialog.setAutoClose(false); // test do not close disklog when finished
                // show % of completion in progress bar
                // timing loop runs thru # of iterations
                // show / run modal dialog
                // NOTE perror is phoney
            
                // test real duration of dialog here
                QElapsedTimer timer_wait;
                timer_wait.start();
            //     futureWatcher.progressValue()
                qDebug()<<"futureWatcher.progressValue() " << futureWatcher.progressValue();
            
            attempt to monitor the actual "value" 
            
                dialog.exec(); // run modal dialog 
            
                qDebug()<<"futureWatcher.progressValue() " << futureWatcher.progressValue();
            

            My attempt to monitor the actual "value" , at least at start and the end of the

            dialog.exec(); // run modal dialog

            Not sure why

            1. the end is set at "10" - should be 100 , but how - default again ?
            2. is it even possible to monitor modal dialog for changes?
              perhaps adding my own slots to connect to QProgressDialog ?
            1 Reply Last reply
            -1
            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #10

              @AnneRanch said in QFutureWatcher - timing issue:

              I do not need my coding style criticized by Peanut gallery .

              I'd avoid getting rude.

              @AnneRanch said in QFutureWatcher - timing issue:

              the end is set at "10" - should be 100 , but how - default again ?

              The dialog creation/initialisation is missing from your code snippet.

              @AnneRanch said in QFutureWatcher - timing issue:

              is it even possible to monitor modal dialog for changes?
              perhaps adding my own slots to connect to QProgressDialog ?

              What monitoring do you have in mind ?

              Interested in AI ? www.idiap.ch
              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

              A 1 Reply Last reply
              0
              • SGaistS SGaist

                @AnneRanch said in QFutureWatcher - timing issue:

                I do not need my coding style criticized by Peanut gallery .

                I'd avoid getting rude.

                @AnneRanch said in QFutureWatcher - timing issue:

                the end is set at "10" - should be 100 , but how - default again ?

                The dialog creation/initialisation is missing from your code snippet.

                @AnneRanch said in QFutureWatcher - timing issue:

                is it even possible to monitor modal dialog for changes?
                perhaps adding my own slots to connect to QProgressDialog ?

                What monitoring do you have in mind ?

                A Offline
                A Offline
                Anonymous_Banned275
                wrote on last edited by
                #11

                @SGaist said in QFutureWatcher - timing issue:

                @AnneRanch said in QFutureWatcher - timing issue:

                I do not need my coding style criticized by Peanut gallery .

                I'd avoid getting rude.

                @AnneRanch said in QFutureWatcher - timing issue:

                the end is set at "10" - should be 100 , but how - default again ?

                The dialog creation/initialisation is missing from your code snippet.

                @AnneRanch said in QFutureWatcher - timing issue:

                is it even possible to monitor modal dialog for changes?
                perhaps adding my own slots to connect to QProgressDialog ?

                What monitoring do you have in mind ?

                As fae as I can tell the QProgressDialog can only follow what QFutureWatcher SIGNALS value and range is being set.
                Since I opeted to use QProgressDialog dialog,exec() I really have no tracking means to see these.
                Of course I could replace the dialog,exec() with code from documents.

                OK, here is my current code - lock , stock and barrel...

                #include "configuredialog.h"
                #include "ui_configuredialog.h"
                #include "project_commonheader.h"
                
                
                ConfigureDialog::ConfigureDialog(QWidget *parent) :
                    QDialog(parent),
                    ui(new Ui::ConfigureDialog)
                {
                    ui->setupUi(this);
                }
                
                ConfigureDialog::~ConfigureDialog()
                {
                    delete ui;
                }
                
                // #of iteration ?? netartion is actaully
                // % step
                // when in 20 it takes steps in 20 %  of total
                // this emulates the time consuming function
                void spin(int& iteration)
                {
                #ifdef PROCESS
                #ifdef TRACE
                    // qDebug() << "QDEBUG TRACE ";
                    qDebug () << " delay spin pass #" << iteration ;
                    qDebug() << "QDEBUG TRACE TASK \n\t\t emulate the time consuming function \n";
                    //qDebug() << "QDEBUG TRACE TASK \n\t\t find nearby BT devices \n";
                #ifdef BYPASS
                    qDebug() << "file     " << __FILE__;
                    qDebug() << "function "<<__FUNCTION__;
                    qDebug() << "@line    " << __LINE__;
                    qDebug()<<"TEMPORARY EXIT ";
                    //exit(99);
                #endif
                #endif
                #endif
                    
                    int static access;
                    if(!access )
                    {
                #ifdef PROCESS
                        qDebug() << "RUN  START long process ....";
                #endif
                        access++;
                    }
                #ifdef PROCESS
                    qDebug() << "RUN  CONTINUE long process ....";
                    
                    // actuall steps MN
                    // adding elapsed timer
                    //    int  Time_Step  = ui->spinBoxIterations_2->text().toInt();
                #endif
                    
                    QElapsedTimer timer;
                    timer.start();
                    //slowOperation();  // we want to measure the time of this slowOperation()
                    // qDebug() << timer.elapsed();
                    //#ifdef BYPASS
                    do
                    {
                        //qDebug() << " do / while timer.elapsed()";
                        ;
                    }while(timer.elapsed() <= 1000); // MN  1 second Time_Step);
                    //#endif
                    
                #ifdef BYPASS
                    const int work = 10000 * 1000 * 33;      // increased by 1000
                    volatile int v = 0;
                    // the time emulator
                    for (int j = 0; j < work; ++j)
                        ++v;                                       // step delay loop MN
                #endif
                    qDebug() << "Estimated single iteration delay elapsed time " << timer.elapsed()<< " mS";
                    
                #ifdef PROCESS
                    qDebug() << "iteration" << iteration << "in thread" << QThread::currentThreadId();
                    //slowOperation();  // we want to measure the time of this slowOperation()
                    qDebug() << "Estimated single iteration delkay elapsed time " << timer.elapsed()<< " mS";
                #endif
                    
                    qDebug() << "iteration # " << iteration << "in thread" << QThread::currentThreadId();
                    
                    
                    
                    
                    
                }
                
                #ifdef BYPASS
                What defaults? The connection, I've shown above and which is used in your example,
                sets up the QProgressDialog according to your QFutureWatchers "watched" work.
                
                progressRangeChanged(int,int) will set the range (0% - 100%) to (0, 10), where 10 = 100%. So each iteration (total of 10) equals 10%.
                        Every time one iteration is done (one iteration = count from 0 to 1000*1000*40), progressValueChanged(int) is emitted and sets the corresponding percentage in your QProgressDialog.
                Then, in the end, waitForFinished() is called to "block" the main thread until all future work has been done (and to ensure that you have all results from all threads, when reaching this point in your code).
                
                Probably your QElapsedTimer causes the issue, because it traps your thread in your do - while loop.
                
                #endif
                // initialize time consuming task
                void ConfigureDialog::on_doTaskButton_clicked()
                {
                    
                    
                # ifdef TRACE
                    qDebug() << "QDEBUG TRACE START void TaskDialog::on_doTaskButton_clicked()";
                    qDebug() << "file     " << __FILE__;
                    qDebug() << "function "<<__FUNCTION__;
                    qDebug() << "@line    " << __LINE__;
                    //qDebug()<<"TEMPORARY EXIT ";
                    //   return;#ifdef BYPASS
                #endif
                    // start run overall timer
                    QElapsedTimer timer;
                    timer.start();
                    
                    // Prepare the vector.
                    // what does it really do ?
                    
                    int iterations = ui->spinBoxIterations->text().toInt();
                    // how may iotera5tions to display 100% competion ??
                    // temporary MN
                    iterations = 10;
                    
                    qDebug()  << " Setup # of iterations = toatal delay " << iterations  << " seconds";
                    
                #ifdef PROCESS
                    qDebug()<<" # of iterations ?? " << iterations ; // vector.append(i) LOOP ";
                    // return;
                    qDebug() << "Estimated elapsed time " << timer.elapsed()<< " mS";
                    // dynamic array # one for each iteration
                    // how often to update progress dialog
                #endif
                    qDebug()  << " Setup # of iterations as vector array ";
                    QVector<int> vector;
                    for (int i = 0; i < iterations; ++i)
                    {
                #ifdef PROCESS
                        //qDebug()<<" interations loop ?? index " << i;
                        qDebug()<<" vector.append(i) index " << i; // LOOP ";
                        // another delay "iterations
                        //qDebug()<<" another delay iterations (?) ";
                #endif
                        vector.append(i);
                    }
                    
                    
                #ifdef BYPASS
                    QLabel *label = new QLabel;
                    QScrollBar *scrollBar = new QScrollBar;
                    QObject::connect(scrollBar, SIGNAL(valueChanged(int)),
                                     label,  SLOT(setNum(int)));
                #endif
                    
                    
                    // return;
                    // Create a progress dialog. implements iteration
                    // shows progress ion %
                    // BUG doe not finish 100%
                    
                    qDebug()<<" Setup Create a QProgressDialog dialog - set paramaters ";
                    // this is a default QProgressDialog constructor
                    //QProgressDialog dialog;
                    //    	QProgressDialog(const QString & labelText,
                    //    const QString & cancelButtonText, int minimum, int maximum,
                    //            QWidget * parent = 0, Qt::WindowFlags f = 0)
                    QProgressDialog dialog ( "TEST window title   ",
                                             " BUTTON text", 0, iterations ,0 ,0);
                    //BUG  did not set to TEST window title  here
                    // dialog.setWindowModality(Qt::WindowModal);
                    
                    //     dialog.labelText(" what is label ?" ); no matching function ??
                    dialog.setWindowTitle("TEST window title  ");
                    
                    dialog.setFixedWidth(500);                    //W.setWindowTitle("TEST window title  ");
                    
                    // set defaulrs  of what ???
                    //    dialog.setMaximum(100);
                    //    dialog.setRange(10, 1000 );
                    
                    //    If set to 0, the dialog is always shown as soon as any progress is set.
                    //    The default is 4000 milliseconds.
                    //    int	minimumDuration() const
                    //    void	setMinimumDuration(int ms)
                    
                    dialog.setMinimumDuration(0);
                    
                    // single shot label only
                    //This is done querying the number of processor cores
                    dialog.setLabelText(QString("Progressing using %1 thread(s)...\nTODO Elapsed time %2  [mS] ")
                                        .arg(QThread::idealThreadCount()).arg(timer.elapsed()));
                    
                    // Create a QFutureWatcher and connect signals and slots.
                    qDebug()<<" Setup Create a QFutureWatcher";
                    QFutureWatcher<void> futureWatcher;
                    
                    qDebug()<<" setup futureWatcher and dialog connect SIGNAL  SLOT ";
                    // # of iterations ?? " << iterations ; // vector.append(i) LOOP ";
                    
                    qDebug()<<" setup future WatcherSIGNAL(finished()";
                    // Resets the progress dialog. The progress dialog becomes hidden if autoClose() is true.
                    //QObject::connect(&futureWatcher, SIGNAL(finished()), &dialog, SLOT(reset())); // reset to what ??
                    
                    
                    qDebug()<<" setup dialog, SIGNAL(canceled()";
                    //QObject::connect(&dialog, SIGNAL(canceled()), &futureWatcher, SLOT(cancel())); // TOK
                    
                    // how to emulate these ??
                    QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)), &dialog, SLOT(setRange(int,int)));
                    QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));
                    
                    // Start the computation.
                    qDebug()<<" Start the computation - ";
                    qDebug()<< "apply delay function spin to each vector";
                    
                    futureWatcher.setFuture(QtConcurrent::map(vector, spin));
                    
                    //  futureWatcher.setFuture();
                    
                    // Display the dialog and start the event loop.
                    qDebug()<<" RUN dialog.exec() Display the dialog and start the dialog event loop";
                    
                    //   dialog.setMaximum(50);
                    // dialog.setRange(10, 50 );
                    
                    qDebug()<<" START dialog.exec() " ; // ? << dialog.setRange(10,30);
                    // progress dialog event loop
                    //dialog.setAutoClose(false); // test do not close disklog when finished
                    // show % of completion in progress bar
                    // timing loop runs thru # of iterations
                    // show / run modal dialog
                    // NOTE perror is phoney
                    
                    // test real duration of dialog here
                    QElapsedTimer timer_wait;
                    timer_wait.start();
                    //     futureWatcher.progressValue()
                    qDebug()<<"futureWatcher.progressValue() " << futureWatcher.progressValue();
                    
                    dialog.exec(); // run modal dialog 
                    
                    qDebug()<<"futureWatcher.progressValue() " << futureWatcher.progressValue();
                    
                    
                    //qDebug()<<" START Display current range " ; // ? << dialog.setRange(10,30);
                #ifdef BYPASS
                    if( dialog.exec())
                        \
                    {
                        perror("Accepted = 1 - sucess ");
                    }
                    else
                    {
                        perror("??  Accepted  != 1  say what ?? ");
                    }
                    ; // timing loop runs thru # of iterations
                #endif
                    qDebug()<<" END dialog.exec() "<< timer_wait.elapsed()<< " mS";
                    //   qDebug() << "test real duration of dialog here " << timer_wait.elapsed()<< " mS";
                    
                    return;
                    
                    qDebug() << "Completed END FULL Estimated elapsed time " << timer.elapsed()<< " mS";
                    
                    // show last iteration result %
                    qDebug()<<"last iteration resul t %  "<< iterations;
                    qDebug()<<" END  Display current range ?? " ; // ? << dialog.setRange(10,30);
                    // qDebug()<<" futureWatcher.waitForFinished()";
                    // when setAUtoCLose is true   defualkt no need to wait for finshed ??
                    // test wait time if any
                    
                    // this makes no snese since connect(&futureWatcher, SIGNAL(finished())
                    // runs &dialog, SLOT(reset())
                    
                #ifdef PROCESS
                    QElapsedTimer timer_wait;
                    timer_wait.start();
                    futureWatcher.waitForFinished();
                    qDebug() << "test wait futureWatcher.waitForFinished()  time if any " << timer_wait.elapsed()<< " mS";
                    
                    // Query the future to check if was canceled.
                    qDebug() << "DONE   (was) Canceled?" << futureWatcher.future().isCanceled();
                #endif
                    
                # ifdef TRACE
                    qDebug() << "QDEBUG TRACE END void TaskDialog::on_doTaskButton_clicked()";
                    qDebug() << "file     " << __FILE__;
                    qDebug() << "function "<<__FUNCTION__;
                    qDebug() << "@line    " << __LINE__;
                    //qDebug()<<"TEMPORARY EXIT ";
                    //   return;#ifdef BYPASS
                #endif
                    
                }
                
                
                #ifdef BYPASS
                
                	QFutureWatcher
                #ifdef BYPASS
                
                \temoprary bypaSS POROIGNAL
                 
                 
                #include "taskdialog.h"
                #include "ui_taskdialog.h"
                #include <QtConcurrent>
                #include <QProgressDialog>
                #include <qtconcurrentmap.h>
                 
                 TaskDialog::TaskDialog(QWidget *parent) :
                     QDialog(parent),
                     ui(new Ui::TaskDialog)
                 {
                     ui->setupUi(this);
                 }
                 
                 TaskDialog::~TaskDialog()
                 {
                     delete ui;
                 }
                 
                 void spin(int& iteration)
                 {
                     const int work = 1000 * 1000 * 40;
                     volatile int v = 0;
                     for (int j = 0; j < work; ++j)
                         ++v;
                     
                     qDebug() << "iteration" << iteration << "in thread" << QThread::currentThreadId();
                 }
                 
                 void TaskDialog::on_doTaskButton_clicked()
                 {
                     
                # ifdef TRACE
                     qDebug() << "QDEBUG TRACE void TaskDialog::on_doTaskButton_clicked()";
                     qDebug() << "file     " << __FILE__;
                     qDebug() << "function "<<__FUNCTION__;
                     qDebug() << "@line    " << __LINE__;
                     qDebug()<<"TEMPORARY EXIT ";
                     return;#ifdef BYPASS
                        #endif
                             
                             
                             // Prepare the vector.
                             int iterations = ui->spinBoxIterations->text().toInt();
                     QVector<int> vector;
                     for (int i = 0; i < iterations; ++i)
                         vector.append(i);
                     
                     // Create a progress dialog.
                     // all defualts ?? no form ??
                     
                     QProgressDialog dialog;
                     
                     dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(QThread::idealThreadCount()));
                     
                     dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(QThread::idealThreadCount()));
                     
                     
                     
                     
                     
                     
                     // Create a QFutureWatcher and connect signals and slots.
                     QFutureWatcher<void> futureWatcher;
                     QObject::connect(&futureWatcher, SIGNAL(finished()), &dialog, SLOT(reset()));
                     QObject::connect(&dialog, SIGNAL(canceled()), &futureWatcher, SLOT(cancel()));
                     QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)), &dialog, SLOT(setRange(int,int)));
                     QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));
                     
                     // Start the computation.
                     // futureWatcher.setFuture(QtConcurrent::map(vector, spin));
                     futureWatcher.setFuture(QtConcurrent::map(vector, spin));
                     
                     // Display the dialog and start the event loop.
                     
                     // this may be wrong
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     dialog.exec();
                     
                     // this may be wrong
                     
                     
                     futureWatcher.waitForFinished();
                     
                     // Query the future to check if was canceled.
                     qDebug() << "Canceled?" << futureWatcher.future().isCanceled();
                 }
                #endif
                 
                 
                 
                #endif
                 
                 
                 
                #ifdef BYPASS
                 // Operation constructor
                 Operation::Operation(QObject *parent)
                     : QObject(parent), steps(0)
                 {
                     pd = new QProgressDialog("Operation in progress.", "Cancel", 0, 100);
                     connect(pd, SIGNAL(canceled()), this, SLOT(cancel()));
                     t = new QTimer(this);
                     connect(t, SIGNAL(timeout()), this, SLOT(perform()));
                     t->start(0);
                 }
                 
                 void Operation::perform()
                 {
                     pd->setValue(steps);
                     //... perform one percent of the operation
                     steps++;
                     if (steps > pd->maximum())
                         t->stop();
                 }
                 
                 void Operation::cancel()
                 {
                     t->stop();
                     //... cleanup
                 }
                 
                 
                #endif
                 
                 
                

                And here is my current output

                QDEBUG TRACE START void TaskDialog::on_doTaskButton_clicked()
                file      ../CAT_V1/configuredialog.cpp
                function  on_doTaskButton_clicked
                @line     111
                 Setup # of iterations = toatal delay  10  seconds
                 Setup # of iterations as vector array 
                 Setup Create a QProgressDialog dialog - set paramaters 
                 Setup Create a QFutureWatcher
                 setup futureWatcher and dialog connect SIGNAL  SLOT 
                 setup future WatcherSIGNAL(finished()
                 setup dialog, SIGNAL(canceled()
                 Start the computation - 
                apply delay function spin to each vector
                 RUN dialog.exec() Display the dialog and start the dialog event loop
                 START dialog.exec() 
                futureWatcher.progressValue()  0
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  0 in thread 0x7f6db5c91700
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  2 in thread 0x7f6d9e581700
                Estimated single iteration delay elapsed time  1004  mS
                iteration #  1 in thread 0x7f6d9d57f700
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  3 in thread 0x7f6d9dd80700
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  4 in thread 0x7f6db5c91700
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  6 in thread 0x7f6d9d57f700
                Estimated single iteration delay elapsed time  1004  mS
                iteration #  5 in thread 0x7f6d9e581700
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  7 in thread 0x7f6d9dd80700
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  8 in thread 0x7f6db5c91700
                Estimated single iteration delay elapsed time  1001  mS
                iteration #  9 in thread 0x7f6d9d57f700
                futureWatcher.progressValue()  10
                 END dialog.exec()  3034  mS
                

                Note the last line - it should be approximately 10 seconds.

                Pl45m4P 1 Reply Last reply
                0
                • A Anonymous_Banned275

                  @SGaist said in QFutureWatcher - timing issue:

                  @AnneRanch said in QFutureWatcher - timing issue:

                  I do not need my coding style criticized by Peanut gallery .

                  I'd avoid getting rude.

                  @AnneRanch said in QFutureWatcher - timing issue:

                  the end is set at "10" - should be 100 , but how - default again ?

                  The dialog creation/initialisation is missing from your code snippet.

                  @AnneRanch said in QFutureWatcher - timing issue:

                  is it even possible to monitor modal dialog for changes?
                  perhaps adding my own slots to connect to QProgressDialog ?

                  What monitoring do you have in mind ?

                  As fae as I can tell the QProgressDialog can only follow what QFutureWatcher SIGNALS value and range is being set.
                  Since I opeted to use QProgressDialog dialog,exec() I really have no tracking means to see these.
                  Of course I could replace the dialog,exec() with code from documents.

                  OK, here is my current code - lock , stock and barrel...

                  #include "configuredialog.h"
                  #include "ui_configuredialog.h"
                  #include "project_commonheader.h"
                  
                  
                  ConfigureDialog::ConfigureDialog(QWidget *parent) :
                      QDialog(parent),
                      ui(new Ui::ConfigureDialog)
                  {
                      ui->setupUi(this);
                  }
                  
                  ConfigureDialog::~ConfigureDialog()
                  {
                      delete ui;
                  }
                  
                  // #of iteration ?? netartion is actaully
                  // % step
                  // when in 20 it takes steps in 20 %  of total
                  // this emulates the time consuming function
                  void spin(int& iteration)
                  {
                  #ifdef PROCESS
                  #ifdef TRACE
                      // qDebug() << "QDEBUG TRACE ";
                      qDebug () << " delay spin pass #" << iteration ;
                      qDebug() << "QDEBUG TRACE TASK \n\t\t emulate the time consuming function \n";
                      //qDebug() << "QDEBUG TRACE TASK \n\t\t find nearby BT devices \n";
                  #ifdef BYPASS
                      qDebug() << "file     " << __FILE__;
                      qDebug() << "function "<<__FUNCTION__;
                      qDebug() << "@line    " << __LINE__;
                      qDebug()<<"TEMPORARY EXIT ";
                      //exit(99);
                  #endif
                  #endif
                  #endif
                      
                      int static access;
                      if(!access )
                      {
                  #ifdef PROCESS
                          qDebug() << "RUN  START long process ....";
                  #endif
                          access++;
                      }
                  #ifdef PROCESS
                      qDebug() << "RUN  CONTINUE long process ....";
                      
                      // actuall steps MN
                      // adding elapsed timer
                      //    int  Time_Step  = ui->spinBoxIterations_2->text().toInt();
                  #endif
                      
                      QElapsedTimer timer;
                      timer.start();
                      //slowOperation();  // we want to measure the time of this slowOperation()
                      // qDebug() << timer.elapsed();
                      //#ifdef BYPASS
                      do
                      {
                          //qDebug() << " do / while timer.elapsed()";
                          ;
                      }while(timer.elapsed() <= 1000); // MN  1 second Time_Step);
                      //#endif
                      
                  #ifdef BYPASS
                      const int work = 10000 * 1000 * 33;      // increased by 1000
                      volatile int v = 0;
                      // the time emulator
                      for (int j = 0; j < work; ++j)
                          ++v;                                       // step delay loop MN
                  #endif
                      qDebug() << "Estimated single iteration delay elapsed time " << timer.elapsed()<< " mS";
                      
                  #ifdef PROCESS
                      qDebug() << "iteration" << iteration << "in thread" << QThread::currentThreadId();
                      //slowOperation();  // we want to measure the time of this slowOperation()
                      qDebug() << "Estimated single iteration delkay elapsed time " << timer.elapsed()<< " mS";
                  #endif
                      
                      qDebug() << "iteration # " << iteration << "in thread" << QThread::currentThreadId();
                      
                      
                      
                      
                      
                  }
                  
                  #ifdef BYPASS
                  What defaults? The connection, I've shown above and which is used in your example,
                  sets up the QProgressDialog according to your QFutureWatchers "watched" work.
                  
                  progressRangeChanged(int,int) will set the range (0% - 100%) to (0, 10), where 10 = 100%. So each iteration (total of 10) equals 10%.
                          Every time one iteration is done (one iteration = count from 0 to 1000*1000*40), progressValueChanged(int) is emitted and sets the corresponding percentage in your QProgressDialog.
                  Then, in the end, waitForFinished() is called to "block" the main thread until all future work has been done (and to ensure that you have all results from all threads, when reaching this point in your code).
                  
                  Probably your QElapsedTimer causes the issue, because it traps your thread in your do - while loop.
                  
                  #endif
                  // initialize time consuming task
                  void ConfigureDialog::on_doTaskButton_clicked()
                  {
                      
                      
                  # ifdef TRACE
                      qDebug() << "QDEBUG TRACE START void TaskDialog::on_doTaskButton_clicked()";
                      qDebug() << "file     " << __FILE__;
                      qDebug() << "function "<<__FUNCTION__;
                      qDebug() << "@line    " << __LINE__;
                      //qDebug()<<"TEMPORARY EXIT ";
                      //   return;#ifdef BYPASS
                  #endif
                      // start run overall timer
                      QElapsedTimer timer;
                      timer.start();
                      
                      // Prepare the vector.
                      // what does it really do ?
                      
                      int iterations = ui->spinBoxIterations->text().toInt();
                      // how may iotera5tions to display 100% competion ??
                      // temporary MN
                      iterations = 10;
                      
                      qDebug()  << " Setup # of iterations = toatal delay " << iterations  << " seconds";
                      
                  #ifdef PROCESS
                      qDebug()<<" # of iterations ?? " << iterations ; // vector.append(i) LOOP ";
                      // return;
                      qDebug() << "Estimated elapsed time " << timer.elapsed()<< " mS";
                      // dynamic array # one for each iteration
                      // how often to update progress dialog
                  #endif
                      qDebug()  << " Setup # of iterations as vector array ";
                      QVector<int> vector;
                      for (int i = 0; i < iterations; ++i)
                      {
                  #ifdef PROCESS
                          //qDebug()<<" interations loop ?? index " << i;
                          qDebug()<<" vector.append(i) index " << i; // LOOP ";
                          // another delay "iterations
                          //qDebug()<<" another delay iterations (?) ";
                  #endif
                          vector.append(i);
                      }
                      
                      
                  #ifdef BYPASS
                      QLabel *label = new QLabel;
                      QScrollBar *scrollBar = new QScrollBar;
                      QObject::connect(scrollBar, SIGNAL(valueChanged(int)),
                                       label,  SLOT(setNum(int)));
                  #endif
                      
                      
                      // return;
                      // Create a progress dialog. implements iteration
                      // shows progress ion %
                      // BUG doe not finish 100%
                      
                      qDebug()<<" Setup Create a QProgressDialog dialog - set paramaters ";
                      // this is a default QProgressDialog constructor
                      //QProgressDialog dialog;
                      //    	QProgressDialog(const QString & labelText,
                      //    const QString & cancelButtonText, int minimum, int maximum,
                      //            QWidget * parent = 0, Qt::WindowFlags f = 0)
                      QProgressDialog dialog ( "TEST window title   ",
                                               " BUTTON text", 0, iterations ,0 ,0);
                      //BUG  did not set to TEST window title  here
                      // dialog.setWindowModality(Qt::WindowModal);
                      
                      //     dialog.labelText(" what is label ?" ); no matching function ??
                      dialog.setWindowTitle("TEST window title  ");
                      
                      dialog.setFixedWidth(500);                    //W.setWindowTitle("TEST window title  ");
                      
                      // set defaulrs  of what ???
                      //    dialog.setMaximum(100);
                      //    dialog.setRange(10, 1000 );
                      
                      //    If set to 0, the dialog is always shown as soon as any progress is set.
                      //    The default is 4000 milliseconds.
                      //    int	minimumDuration() const
                      //    void	setMinimumDuration(int ms)
                      
                      dialog.setMinimumDuration(0);
                      
                      // single shot label only
                      //This is done querying the number of processor cores
                      dialog.setLabelText(QString("Progressing using %1 thread(s)...\nTODO Elapsed time %2  [mS] ")
                                          .arg(QThread::idealThreadCount()).arg(timer.elapsed()));
                      
                      // Create a QFutureWatcher and connect signals and slots.
                      qDebug()<<" Setup Create a QFutureWatcher";
                      QFutureWatcher<void> futureWatcher;
                      
                      qDebug()<<" setup futureWatcher and dialog connect SIGNAL  SLOT ";
                      // # of iterations ?? " << iterations ; // vector.append(i) LOOP ";
                      
                      qDebug()<<" setup future WatcherSIGNAL(finished()";
                      // Resets the progress dialog. The progress dialog becomes hidden if autoClose() is true.
                      //QObject::connect(&futureWatcher, SIGNAL(finished()), &dialog, SLOT(reset())); // reset to what ??
                      
                      
                      qDebug()<<" setup dialog, SIGNAL(canceled()";
                      //QObject::connect(&dialog, SIGNAL(canceled()), &futureWatcher, SLOT(cancel())); // TOK
                      
                      // how to emulate these ??
                      QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)), &dialog, SLOT(setRange(int,int)));
                      QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));
                      
                      // Start the computation.
                      qDebug()<<" Start the computation - ";
                      qDebug()<< "apply delay function spin to each vector";
                      
                      futureWatcher.setFuture(QtConcurrent::map(vector, spin));
                      
                      //  futureWatcher.setFuture();
                      
                      // Display the dialog and start the event loop.
                      qDebug()<<" RUN dialog.exec() Display the dialog and start the dialog event loop";
                      
                      //   dialog.setMaximum(50);
                      // dialog.setRange(10, 50 );
                      
                      qDebug()<<" START dialog.exec() " ; // ? << dialog.setRange(10,30);
                      // progress dialog event loop
                      //dialog.setAutoClose(false); // test do not close disklog when finished
                      // show % of completion in progress bar
                      // timing loop runs thru # of iterations
                      // show / run modal dialog
                      // NOTE perror is phoney
                      
                      // test real duration of dialog here
                      QElapsedTimer timer_wait;
                      timer_wait.start();
                      //     futureWatcher.progressValue()
                      qDebug()<<"futureWatcher.progressValue() " << futureWatcher.progressValue();
                      
                      dialog.exec(); // run modal dialog 
                      
                      qDebug()<<"futureWatcher.progressValue() " << futureWatcher.progressValue();
                      
                      
                      //qDebug()<<" START Display current range " ; // ? << dialog.setRange(10,30);
                  #ifdef BYPASS
                      if( dialog.exec())
                          \
                      {
                          perror("Accepted = 1 - sucess ");
                      }
                      else
                      {
                          perror("??  Accepted  != 1  say what ?? ");
                      }
                      ; // timing loop runs thru # of iterations
                  #endif
                      qDebug()<<" END dialog.exec() "<< timer_wait.elapsed()<< " mS";
                      //   qDebug() << "test real duration of dialog here " << timer_wait.elapsed()<< " mS";
                      
                      return;
                      
                      qDebug() << "Completed END FULL Estimated elapsed time " << timer.elapsed()<< " mS";
                      
                      // show last iteration result %
                      qDebug()<<"last iteration resul t %  "<< iterations;
                      qDebug()<<" END  Display current range ?? " ; // ? << dialog.setRange(10,30);
                      // qDebug()<<" futureWatcher.waitForFinished()";
                      // when setAUtoCLose is true   defualkt no need to wait for finshed ??
                      // test wait time if any
                      
                      // this makes no snese since connect(&futureWatcher, SIGNAL(finished())
                      // runs &dialog, SLOT(reset())
                      
                  #ifdef PROCESS
                      QElapsedTimer timer_wait;
                      timer_wait.start();
                      futureWatcher.waitForFinished();
                      qDebug() << "test wait futureWatcher.waitForFinished()  time if any " << timer_wait.elapsed()<< " mS";
                      
                      // Query the future to check if was canceled.
                      qDebug() << "DONE   (was) Canceled?" << futureWatcher.future().isCanceled();
                  #endif
                      
                  # ifdef TRACE
                      qDebug() << "QDEBUG TRACE END void TaskDialog::on_doTaskButton_clicked()";
                      qDebug() << "file     " << __FILE__;
                      qDebug() << "function "<<__FUNCTION__;
                      qDebug() << "@line    " << __LINE__;
                      //qDebug()<<"TEMPORARY EXIT ";
                      //   return;#ifdef BYPASS
                  #endif
                      
                  }
                  
                  
                  #ifdef BYPASS
                  
                  	QFutureWatcher
                  #ifdef BYPASS
                  
                  \temoprary bypaSS POROIGNAL
                   
                   
                  #include "taskdialog.h"
                  #include "ui_taskdialog.h"
                  #include <QtConcurrent>
                  #include <QProgressDialog>
                  #include <qtconcurrentmap.h>
                   
                   TaskDialog::TaskDialog(QWidget *parent) :
                       QDialog(parent),
                       ui(new Ui::TaskDialog)
                   {
                       ui->setupUi(this);
                   }
                   
                   TaskDialog::~TaskDialog()
                   {
                       delete ui;
                   }
                   
                   void spin(int& iteration)
                   {
                       const int work = 1000 * 1000 * 40;
                       volatile int v = 0;
                       for (int j = 0; j < work; ++j)
                           ++v;
                       
                       qDebug() << "iteration" << iteration << "in thread" << QThread::currentThreadId();
                   }
                   
                   void TaskDialog::on_doTaskButton_clicked()
                   {
                       
                  # ifdef TRACE
                       qDebug() << "QDEBUG TRACE void TaskDialog::on_doTaskButton_clicked()";
                       qDebug() << "file     " << __FILE__;
                       qDebug() << "function "<<__FUNCTION__;
                       qDebug() << "@line    " << __LINE__;
                       qDebug()<<"TEMPORARY EXIT ";
                       return;#ifdef BYPASS
                          #endif
                               
                               
                               // Prepare the vector.
                               int iterations = ui->spinBoxIterations->text().toInt();
                       QVector<int> vector;
                       for (int i = 0; i < iterations; ++i)
                           vector.append(i);
                       
                       // Create a progress dialog.
                       // all defualts ?? no form ??
                       
                       QProgressDialog dialog;
                       
                       dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(QThread::idealThreadCount()));
                       
                       dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(QThread::idealThreadCount()));
                       
                       
                       
                       
                       
                       
                       // Create a QFutureWatcher and connect signals and slots.
                       QFutureWatcher<void> futureWatcher;
                       QObject::connect(&futureWatcher, SIGNAL(finished()), &dialog, SLOT(reset()));
                       QObject::connect(&dialog, SIGNAL(canceled()), &futureWatcher, SLOT(cancel()));
                       QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)), &dialog, SLOT(setRange(int,int)));
                       QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));
                       
                       // Start the computation.
                       // futureWatcher.setFuture(QtConcurrent::map(vector, spin));
                       futureWatcher.setFuture(QtConcurrent::map(vector, spin));
                       
                       // Display the dialog and start the event loop.
                       
                       // this may be wrong
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       dialog.exec();
                       
                       // this may be wrong
                       
                       
                       futureWatcher.waitForFinished();
                       
                       // Query the future to check if was canceled.
                       qDebug() << "Canceled?" << futureWatcher.future().isCanceled();
                   }
                  #endif
                   
                   
                   
                  #endif
                   
                   
                   
                  #ifdef BYPASS
                   // Operation constructor
                   Operation::Operation(QObject *parent)
                       : QObject(parent), steps(0)
                   {
                       pd = new QProgressDialog("Operation in progress.", "Cancel", 0, 100);
                       connect(pd, SIGNAL(canceled()), this, SLOT(cancel()));
                       t = new QTimer(this);
                       connect(t, SIGNAL(timeout()), this, SLOT(perform()));
                       t->start(0);
                   }
                   
                   void Operation::perform()
                   {
                       pd->setValue(steps);
                       //... perform one percent of the operation
                       steps++;
                       if (steps > pd->maximum())
                           t->stop();
                   }
                   
                   void Operation::cancel()
                   {
                       t->stop();
                       //... cleanup
                   }
                   
                   
                  #endif
                   
                   
                  

                  And here is my current output

                  QDEBUG TRACE START void TaskDialog::on_doTaskButton_clicked()
                  file      ../CAT_V1/configuredialog.cpp
                  function  on_doTaskButton_clicked
                  @line     111
                   Setup # of iterations = toatal delay  10  seconds
                   Setup # of iterations as vector array 
                   Setup Create a QProgressDialog dialog - set paramaters 
                   Setup Create a QFutureWatcher
                   setup futureWatcher and dialog connect SIGNAL  SLOT 
                   setup future WatcherSIGNAL(finished()
                   setup dialog, SIGNAL(canceled()
                   Start the computation - 
                  apply delay function spin to each vector
                   RUN dialog.exec() Display the dialog and start the dialog event loop
                   START dialog.exec() 
                  futureWatcher.progressValue()  0
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  0 in thread 0x7f6db5c91700
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  2 in thread 0x7f6d9e581700
                  Estimated single iteration delay elapsed time  1004  mS
                  iteration #  1 in thread 0x7f6d9d57f700
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  3 in thread 0x7f6d9dd80700
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  4 in thread 0x7f6db5c91700
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  6 in thread 0x7f6d9d57f700
                  Estimated single iteration delay elapsed time  1004  mS
                  iteration #  5 in thread 0x7f6d9e581700
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  7 in thread 0x7f6d9dd80700
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  8 in thread 0x7f6db5c91700
                  Estimated single iteration delay elapsed time  1001  mS
                  iteration #  9 in thread 0x7f6d9d57f700
                  futureWatcher.progressValue()  10
                   END dialog.exec()  3034  mS
                  

                  Note the last line - it should be approximately 10 seconds.

                  Pl45m4P Offline
                  Pl45m4P Offline
                  Pl45m4
                  wrote on last edited by
                  #12

                  @AnneRanch said in QFutureWatcher - timing issue:

                  Note the last line - it should be approximately 10 seconds.

                  Is this your only issue?! Are you aware that QElapsedTimer only counts the seconds from last (re-)start?!
                  So if you restart the same timer multiple times, it measures the time from last start to end only.

                  Can you confirm that every single task needs about one 1 second?! Or is this output wrong and it only takes 3 secs for all 10 tasks, which should take 10?


                  If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                  ~E. W. Dijkstra

                  A 1 Reply Last reply
                  1
                  • Pl45m4P Pl45m4

                    @AnneRanch said in QFutureWatcher - timing issue:

                    Note the last line - it should be approximately 10 seconds.

                    Is this your only issue?! Are you aware that QElapsedTimer only counts the seconds from last (re-)start?!
                    So if you restart the same timer multiple times, it measures the time from last start to end only.

                    Can you confirm that every single task needs about one 1 second?! Or is this output wrong and it only takes 3 secs for all 10 tasks, which should take 10?

                    A Offline
                    A Offline
                    Anonymous_Banned275
                    wrote on last edited by
                    #13

                    @Pl45m4 said in QFutureWatcher - timing issue:

                    @AnneRanch said in QFutureWatcher - timing issue:

                    Note the last line - it should be approximately 10 seconds.

                    Is this your only issue?! ''
                    YES

                    Are you aware that QElapsedTimer only counts the seconds from last (re-)start?!

                    YES

                    So if you restart the same timer multiple times, it measures the time from last start to end only.

                    Name specific time that is incorrectly restarted that way .

                    Can you confirm that every single task needs about one 1 second?!
                    YES
                    I am after 10 seconds delay, using 10 iterations that = approximately 10 * 1 seconds. The time precision is irrelevant.

                    Or is this output wrong and it only takes 3 secs for all 10 tasks, which should take 10?

                    YES

                    The desired execution of dialog.exec() is 10 seconds - the current execution takes approximately 3 seconds.

                    Here is a crazy idea
                    If I set the iteration to 50 - the total delay time is approximately 13
                    seconds.

                    If I set the iteration to 100 - the total delay time is approximately 25 seconds.

                    The "spin" delay runs in its own thread - which is not necessary since the delay is cumulative - no need for parallel processing.

                    BUT the dialog.exec() "uses" all four CPU cores ( as noted in the progress dialog text ) - hence four threads .
                    Thinking up-loud - since each iteration runs in four threads - is the delay really 1 second? Sounds really crazy...
                    Keeping in mind that I really do not have means monitoring the dialog.exec()
                    iterations.
                    Could that be the issue?

                    I should be able to track both SIGNALS - I 'll take a look how it can be done.

                    kshegunovK 1 Reply Last reply
                    0
                    • A Anonymous_Banned275

                      @Pl45m4 said in QFutureWatcher - timing issue:

                      @AnneRanch said in QFutureWatcher - timing issue:

                      Note the last line - it should be approximately 10 seconds.

                      Is this your only issue?! ''
                      YES

                      Are you aware that QElapsedTimer only counts the seconds from last (re-)start?!

                      YES

                      So if you restart the same timer multiple times, it measures the time from last start to end only.

                      Name specific time that is incorrectly restarted that way .

                      Can you confirm that every single task needs about one 1 second?!
                      YES
                      I am after 10 seconds delay, using 10 iterations that = approximately 10 * 1 seconds. The time precision is irrelevant.

                      Or is this output wrong and it only takes 3 secs for all 10 tasks, which should take 10?

                      YES

                      The desired execution of dialog.exec() is 10 seconds - the current execution takes approximately 3 seconds.

                      Here is a crazy idea
                      If I set the iteration to 50 - the total delay time is approximately 13
                      seconds.

                      If I set the iteration to 100 - the total delay time is approximately 25 seconds.

                      The "spin" delay runs in its own thread - which is not necessary since the delay is cumulative - no need for parallel processing.

                      BUT the dialog.exec() "uses" all four CPU cores ( as noted in the progress dialog text ) - hence four threads .
                      Thinking up-loud - since each iteration runs in four threads - is the delay really 1 second? Sounds really crazy...
                      Keeping in mind that I really do not have means monitoring the dialog.exec()
                      iterations.
                      Could that be the issue?

                      I should be able to track both SIGNALS - I 'll take a look how it can be done.

                      kshegunovK Offline
                      kshegunovK Offline
                      kshegunov
                      Moderators
                      wrote on last edited by
                      #14

                      @AnneRanch said in QFutureWatcher - timing issue:

                      The "spin" delay runs in its own thread - which is not necessary since the delay is cumulative

                      In its own threads.

                      - no need for parallel processing.

                      Then why do you explicitly use parallel processing? ... then wonder why the time is approximately scaled by the number of pooled threads ... this is all very confusing ...

                      BUT the dialog.exec() "uses" all four CPU cores ( as noted in the progress dialog text ) - hence four threads .

                      QDialog::exec doesn't use any cores at all. Your QtConcurrent::map does.

                      Keeping in mind that I really do not have means monitoring the dialog.exec()
                      iterations.

                      There are no iterations. QDialog::exec waits for an event to appear in the event queue, if there's none it just sleeps until one happens to appear (be it a GUI event or a signal/slot meta-call - a.k.a. queued connection call).

                      Read and abide by the Qt Code of Conduct

                      A 1 Reply Last reply
                      2
                      • kshegunovK kshegunov

                        @AnneRanch said in QFutureWatcher - timing issue:

                        The "spin" delay runs in its own thread - which is not necessary since the delay is cumulative

                        In its own threads.

                        - no need for parallel processing.

                        Then why do you explicitly use parallel processing? ... then wonder why the time is approximately scaled by the number of pooled threads ... this is all very confusing ...

                        BUT the dialog.exec() "uses" all four CPU cores ( as noted in the progress dialog text ) - hence four threads .

                        QDialog::exec doesn't use any cores at all. Your QtConcurrent::map does.

                        Keeping in mind that I really do not have means monitoring the dialog.exec()
                        iterations.

                        There are no iterations. QDialog::exec waits for an event to appear in the event queue, if there's none it just sleeps until one happens to appear (be it a GUI event or a signal/slot meta-call - a.k.a. queued connection call).

                        A Offline
                        A Offline
                        Anonymous_Banned275
                        wrote on last edited by Anonymous_Banned275
                        #15

                        @kshegunov said in QFutureWatcher - timing issue:

                        @AnneRanch said in QFutureWatcher - timing issue:

                        The "spin" delay runs in its own thread - which is not necessary since the delay is cumulative

                        In its own threads.

                        - no need for parallel processing.

                        Then why do you explicitly use parallel processing? ... then wonder why the time is approximately scaled by the number of pooled threads ... this is all very confusing ...

                        As pointed out many times - I am following a tutorial.
                        I have also said that most of the tutorial steps are not commented WHAT they do . Basically blindly following the tutorial - and the result is obvious.
                        Confusing to you , frustrating to me.

                        BUT the dialog.exec() "uses" all four CPU cores ( as noted in the progress dialog text ) - hence four threads .

                        Which does not make sense.

                        QDialog::exec doesn't use any cores at all. Your QtConcurrent::map does.

                        Keeping in mind that I really do not have means monitoring the dialog.exec()
                        iterations.

                        I do not like to get sidteracked by niticking on sentic.
                        The QProgresDialog ( n tutorial ) outputs

                        dialog.setLabelText(QString("Progressing using %1 thread(s)...\nTODO Elapsed time %2  [mS] ")
                                            .arg(QThread::idealThreadCount()).arg(timer.elapsed()));
                        

                        So why should I question WHO is using the threads - dialog or QtConcurrent?

                        How does that leads to solution ?
                        I am not complaining about your comment, just trying to maintain some priorities in logic to find the problem.

                        > There are no iterations. QDialog::exec waits for an event to appear in the event queue, if there's none it just sleeps until one happens to appear (be it a GUI event or a signal/slot meta-call - a.k.a. queued connection call).

                        **OK THIS IS VERY GOOD POINT and IMPORTANT,

                        My test delay process is initialized by standard button push...
                        "" can somebody describe WHAT EVENT actually starts QProgressDialog::exec ?**

                        I am under the impression that QProgressDialog constructor does that.
                        Am I wrong ?

                        And HOW does the delay process continue from starting point ?

                        Secondly
                        so what are "iterations" for ?
                        They are passed to QProgressDialog constructor...

                        Challenge to group
                        Would somebody some up with old fashioned flow chart to put the process
                        from "button pushed" to "delay completed " ?
                        My verbal output track sort of does it , but obviously needs better explanations what each step does.

                        New crazy thought - the original tutorial code worked (!) but it used default
                        constructor - without any parameters passed to the class and without setting any parameters in code - just used all unpublished defaults.
                        With one of the defaults , forgot which one, the actual progress bar supposedly should show up AFTER 4 second delay .

                        In current failure mode the progress bar shows 10% (immediately) then shows 50% ( after about 3 seconds) - the percentage is exactly "4 seconds " between the updates when iteration is set to 10 !

                        kshegunovK 1 Reply Last reply
                        0
                        • A Anonymous_Banned275

                          @kshegunov said in QFutureWatcher - timing issue:

                          @AnneRanch said in QFutureWatcher - timing issue:

                          The "spin" delay runs in its own thread - which is not necessary since the delay is cumulative

                          In its own threads.

                          - no need for parallel processing.

                          Then why do you explicitly use parallel processing? ... then wonder why the time is approximately scaled by the number of pooled threads ... this is all very confusing ...

                          As pointed out many times - I am following a tutorial.
                          I have also said that most of the tutorial steps are not commented WHAT they do . Basically blindly following the tutorial - and the result is obvious.
                          Confusing to you , frustrating to me.

                          BUT the dialog.exec() "uses" all four CPU cores ( as noted in the progress dialog text ) - hence four threads .

                          Which does not make sense.

                          QDialog::exec doesn't use any cores at all. Your QtConcurrent::map does.

                          Keeping in mind that I really do not have means monitoring the dialog.exec()
                          iterations.

                          I do not like to get sidteracked by niticking on sentic.
                          The QProgresDialog ( n tutorial ) outputs

                          dialog.setLabelText(QString("Progressing using %1 thread(s)...\nTODO Elapsed time %2  [mS] ")
                                              .arg(QThread::idealThreadCount()).arg(timer.elapsed()));
                          

                          So why should I question WHO is using the threads - dialog or QtConcurrent?

                          How does that leads to solution ?
                          I am not complaining about your comment, just trying to maintain some priorities in logic to find the problem.

                          > There are no iterations. QDialog::exec waits for an event to appear in the event queue, if there's none it just sleeps until one happens to appear (be it a GUI event or a signal/slot meta-call - a.k.a. queued connection call).

                          **OK THIS IS VERY GOOD POINT and IMPORTANT,

                          My test delay process is initialized by standard button push...
                          "" can somebody describe WHAT EVENT actually starts QProgressDialog::exec ?**

                          I am under the impression that QProgressDialog constructor does that.
                          Am I wrong ?

                          And HOW does the delay process continue from starting point ?

                          Secondly
                          so what are "iterations" for ?
                          They are passed to QProgressDialog constructor...

                          Challenge to group
                          Would somebody some up with old fashioned flow chart to put the process
                          from "button pushed" to "delay completed " ?
                          My verbal output track sort of does it , but obviously needs better explanations what each step does.

                          New crazy thought - the original tutorial code worked (!) but it used default
                          constructor - without any parameters passed to the class and without setting any parameters in code - just used all unpublished defaults.
                          With one of the defaults , forgot which one, the actual progress bar supposedly should show up AFTER 4 second delay .

                          In current failure mode the progress bar shows 10% (immediately) then shows 50% ( after about 3 seconds) - the percentage is exactly "4 seconds " between the updates when iteration is set to 10 !

                          kshegunovK Offline
                          kshegunovK Offline
                          kshegunov
                          Moderators
                          wrote on last edited by kshegunov
                          #16

                          @AnneRanch said in QFutureWatcher - timing issue:

                          As pointed out many times - I am following a tutorial.
                          I have also said that most of the tutorial steps are not commented WHAT they do . Basically blindly following the tutorial - and the result is obvious.

                          Then read in docs what they do so you understand it, at least that's my advice. QtConcurrent::map isn't an alien we need a team of scientists to talk to, right? Just look it up, that's what I do when I follow tutorials.

                          Confusing to you , frustrating to me.

                          Yes, yes, frustration leads to anger, anger leads to the dark side and all that. Less emotion, more practicality helps, I've found out.

                          I do not like to get sidteracked by niticking on sentic.

                          Actually you do, you just don't realize it. You have an unknown machine you're trying to figure out, but you claim you're not interested in how the cogs it's made of fit together. Should I mention such an approach is utterly futile?

                          The QProgresDialog ( n tutorial ) outputs

                          dialog.setLabelText(QString("Progressing using %1 thread(s)...\nTODO Elapsed time %2  [mS] ")
                                              .arg(QThread::idealThreadCount()).arg(timer.elapsed()));
                          

                          So? This is evaluated before the dialog is even shown to the screen and has nothing to do with the dialog itself.

                          So why shoudI question WHO is using the threads - dialog or QtConcurren ?

                          It should, so you know where the problem lies. If you don't understand where the error is, then you're not going to be able to fix it, ever.

                          How does that leads to solution?

                          I don't know exactly what kind of solution you expect as I can't seem to fathom the problem. You split and process some vector in several threads, I get that. But I don't get what times and delays and elapsed timers have to do with it ...

                          For reference, what's the output of the following snippet:

                          QObject::connect(&futureWatcher, &decltype(futureWatcher)::progressRangeChanged, [] (int from, int to) -> void  {
                              qDebug() << "Map from " << from << " to " << to;
                          });
                          QObject::connect(&futureWatcher, &decltype(futureWatcher)::progressValueChanged, [] (int value) -> void  {
                              qDebug() << "Map progress: " << value;
                          });

                          Read and abide by the Qt Code of Conduct

                          1 Reply Last reply
                          2
                          • A Offline
                            A Offline
                            Anonymous_Banned275
                            wrote on last edited by
                            #17

                            Assuming the QprogressDialog is advanced / controlled by QFutureWacher SIGNALs of :"value" and "range"

                            I have added means of monitoring these signals

                             // create test SLOT to monitor progressValueChanged(int)
                            

                            qDebug() << "create test SLOT to monitor progressValueChanged(int)";
                            QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), this, SLOT(on_doTaskButton_2_clicked));
                            QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)),this, SLOT(on_doTaskButton_3_clicked)));

                            The result output is here

                             Start the computation - 
                            apply delay function spin to each vector
                             RUN dialog.exec() Display the dialog and start the dialog event loop
                             START dialog.exec() 
                            futureWatcher.progressValue()  0
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  0
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  1
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  0 in thread 0x7f380b7fe700
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  1 in thread 0x7f37fbfff700
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  2
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  3
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  2 in thread 0x7f3808eea700
                            Estimated single iteration delay elapsed time  1008  mS
                            iteration #  3 in thread 0x7f37fb7fe700
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  4
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  5
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  5 in thread 0x7f37fbfff700
                            Estimated single iteration delay elapsed time  1008  mS
                            iteration #  4 in thread 0x7f380b7fe700
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  6
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  6 in thread 0x7f3808eea700
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  7
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  7 in thread 0x7f37fb7fe700
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  8 in thread 0x7f37fbfff700
                            Estimated single iteration delay elapsed time  1001  mS
                            iteration #  9 in thread 0x7f380b7fe700
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  8
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  9
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  10
                            QDEBUG TRACE track  SIGNAL SLOT
                            file      ../CAT_V1/configuredialog.cpp
                            function  on_doTaskButton_2_clicked
                            @line     512
                             SLOT value access  11
                            futureWatcher.progressValue()  10
                             END dialog.exec()  3030  mS
                            

                            Conclusion
                            the SIGNAL monitoring the value is changed 11 times - pretty much what is expected. I'll add showing the actual "value" at each time int changes - just to further verify it - it should be 10, 20, 30 etc.

                            The range does not change and it should not - should remain 0 thru 100.

                            kshegunovK 1 Reply Last reply
                            0
                            • A Anonymous_Banned275

                              Assuming the QprogressDialog is advanced / controlled by QFutureWacher SIGNALs of :"value" and "range"

                              I have added means of monitoring these signals

                               // create test SLOT to monitor progressValueChanged(int)
                              

                              qDebug() << "create test SLOT to monitor progressValueChanged(int)";
                              QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), this, SLOT(on_doTaskButton_2_clicked));
                              QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)),this, SLOT(on_doTaskButton_3_clicked)));

                              The result output is here

                               Start the computation - 
                              apply delay function spin to each vector
                               RUN dialog.exec() Display the dialog and start the dialog event loop
                               START dialog.exec() 
                              futureWatcher.progressValue()  0
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  0
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  1
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  0 in thread 0x7f380b7fe700
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  1 in thread 0x7f37fbfff700
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  2
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  3
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  2 in thread 0x7f3808eea700
                              Estimated single iteration delay elapsed time  1008  mS
                              iteration #  3 in thread 0x7f37fb7fe700
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  4
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  5
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  5 in thread 0x7f37fbfff700
                              Estimated single iteration delay elapsed time  1008  mS
                              iteration #  4 in thread 0x7f380b7fe700
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  6
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  6 in thread 0x7f3808eea700
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  7
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  7 in thread 0x7f37fb7fe700
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  8 in thread 0x7f37fbfff700
                              Estimated single iteration delay elapsed time  1001  mS
                              iteration #  9 in thread 0x7f380b7fe700
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  8
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  9
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  10
                              QDEBUG TRACE track  SIGNAL SLOT
                              file      ../CAT_V1/configuredialog.cpp
                              function  on_doTaskButton_2_clicked
                              @line     512
                               SLOT value access  11
                              futureWatcher.progressValue()  10
                               END dialog.exec()  3030  mS
                              

                              Conclusion
                              the SIGNAL monitoring the value is changed 11 times - pretty much what is expected. I'll add showing the actual "value" at each time int changes - just to further verify it - it should be 10, 20, 30 etc.

                              The range does not change and it should not - should remain 0 thru 100.

                              kshegunovK Offline
                              kshegunovK Offline
                              kshegunov
                              Moderators
                              wrote on last edited by
                              #18

                              @AnneRanch said in QFutureWatcher - timing issue:

                              The range does not change and it should not - should remain 0 thru 100.

                              I somehow doubt that assertion, more specifically the numbers you cite, and the conclusions you draw from it. This is why I requested the output from the snippet in my previous post.

                              Read and abide by the Qt Code of Conduct

                              1 Reply Last reply
                              1
                              • A Offline
                                A Offline
                                Anonymous_Banned275
                                wrote on last edited by
                                #19

                                "Programs written with QtConcurrent automatically adjust the number of threads used according to the number of processor cores available. "

                                Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.
                                Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.
                                Thus the total desired time delay is incorrect.

                                Pl45m4P 1 Reply Last reply
                                0
                                • A Anonymous_Banned275

                                  "Programs written with QtConcurrent automatically adjust the number of threads used according to the number of processor cores available. "

                                  Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.
                                  Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.
                                  Thus the total desired time delay is incorrect.

                                  Pl45m4P Offline
                                  Pl45m4P Offline
                                  Pl45m4
                                  wrote on last edited by Pl45m4
                                  #20

                                  @AnneRanch said in QFutureWatcher - timing issue:

                                  FOUR times faster.

                                  Four threads won't increase the processing time of your whole task by a factor of four (if they share the same data)

                                  Might be interesting:
                                  (esp. the Concurrent part)

                                  • https://www.logicbig.com/quick-info/programming/multi-threading.html

                                  If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                                  ~E. W. Dijkstra

                                  A 1 Reply Last reply
                                  1
                                  • Pl45m4P Pl45m4

                                    @AnneRanch said in QFutureWatcher - timing issue:

                                    FOUR times faster.

                                    Four threads won't increase the processing time of your whole task by a factor of four (if they share the same data)

                                    Might be interesting:
                                    (esp. the Concurrent part)

                                    • https://www.logicbig.com/quick-info/programming/multi-threading.html
                                    A Offline
                                    A Offline
                                    Anonymous_Banned275
                                    wrote on last edited by
                                    #21

                                    @Pl45m4 said in QFutureWatcher - timing issue:

                                    @AnneRanch said in QFutureWatcher - timing issue:

                                    FOUR times faster.

                                    Four threads won't increase the processing time of your whole task by a factor of four (if they share the same data)

                                    Might be interesting:
                                    (esp. the Concurrent part)

                                    • https://www.logicbig.com/quick-info/programming/multi-threading.html

                                    Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.
                                    Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.
                                    Thus the total desired time delay is incorrect.

                                    SGaistS kshegunovK 2 Replies Last reply
                                    0
                                    • A Anonymous_Banned275

                                      @Pl45m4 said in QFutureWatcher - timing issue:

                                      @AnneRanch said in QFutureWatcher - timing issue:

                                      FOUR times faster.

                                      Four threads won't increase the processing time of your whole task by a factor of four (if they share the same data)

                                      Might be interesting:
                                      (esp. the Concurrent part)

                                      • https://www.logicbig.com/quick-info/programming/multi-threading.html

                                      Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.
                                      Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.
                                      Thus the total desired time delay is incorrect.

                                      SGaistS Offline
                                      SGaistS Offline
                                      SGaist
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #22

                                      @AnneRanch said in QFutureWatcher - timing issue:

                                      Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.
                                      Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.
                                      Thus the total desired time delay is incorrect.

                                      You are using the wrong assumption that the four cores of your machine are each running exclusively one of these tasks.

                                      They are not. Your processor cores are shared and runs variety of tasks from which your application and its threads.

                                      Just take a look at your platform system analyser. You'll see that there's a lot happening under the hood.

                                      Interested in AI ? www.idiap.ch
                                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                      A 1 Reply Last reply
                                      2
                                      • A Anonymous_Banned275

                                        @Pl45m4 said in QFutureWatcher - timing issue:

                                        @AnneRanch said in QFutureWatcher - timing issue:

                                        FOUR times faster.

                                        Four threads won't increase the processing time of your whole task by a factor of four (if they share the same data)

                                        Might be interesting:
                                        (esp. the Concurrent part)

                                        • https://www.logicbig.com/quick-info/programming/multi-threading.html

                                        Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.
                                        Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.
                                        Thus the total desired time delay is incorrect.

                                        kshegunovK Offline
                                        kshegunovK Offline
                                        kshegunov
                                        Moderators
                                        wrote on last edited by
                                        #23

                                        @AnneRanch said in QFutureWatcher - timing issue:

                                        Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.

                                        Hm, very weird, if only someone had mentioned this before ...!

                                        Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.

                                        Approximately. Which is the whole point of running anything in parallel.

                                        Thus the total desired time delay is incorrect.

                                        There's no such thing, I believe I already said that on more than one occasion. GUI programming is event driven, there's no specific time for waiting, or specific order in which things happen; you get events, you respond to events, this is all. If it takes 3 seconds or 5, or 10 seconds or an hour is beside the point. When the event/signal is sent/emitted, then you process it and this is all ...

                                        @SGaist said in QFutureWatcher - timing issue:

                                        You are using the wrong assumption that the four cores of your machine are each running exclusively one of these tasks.

                                        It's possible, albeit rather rare.

                                        @Pl45m4 said in QFutureWatcher - timing issue:

                                        Four threads won't increase the processing time of your whole task by a factor of four (if they share the same data)

                                        Actually, they should. They usually don't as per Amdahl's law. I've a piece I'd written for work that scales almost perfectly with the number of cores, however the task I'd implemented is such that it is extremely parallelizable.

                                        Read and abide by the Qt Code of Conduct

                                        Pl45m4P 1 Reply Last reply
                                        2
                                        • kshegunovK kshegunov

                                          @AnneRanch said in QFutureWatcher - timing issue:

                                          Hence there is no single usage of QFuture vectors - but FOUR of them are used running in four CPU cores at once.

                                          Hm, very weird, if only someone had mentioned this before ...!

                                          Hence QProgressDialog "runs out" the correctly timed iterations FOUR times faster.

                                          Approximately. Which is the whole point of running anything in parallel.

                                          Thus the total desired time delay is incorrect.

                                          There's no such thing, I believe I already said that on more than one occasion. GUI programming is event driven, there's no specific time for waiting, or specific order in which things happen; you get events, you respond to events, this is all. If it takes 3 seconds or 5, or 10 seconds or an hour is beside the point. When the event/signal is sent/emitted, then you process it and this is all ...

                                          @SGaist said in QFutureWatcher - timing issue:

                                          You are using the wrong assumption that the four cores of your machine are each running exclusively one of these tasks.

                                          It's possible, albeit rather rare.

                                          @Pl45m4 said in QFutureWatcher - timing issue:

                                          Four threads won't increase the processing time of your whole task by a factor of four (if they share the same data)

                                          Actually, they should. They usually don't as per Amdahl's law. I've a piece I'd written for work that scales almost perfectly with the number of cores, however the task I'd implemented is such that it is extremely parallelizable.

                                          Pl45m4P Offline
                                          Pl45m4P Offline
                                          Pl45m4
                                          wrote on last edited by
                                          #24

                                          @kshegunov said in QFutureWatcher - timing issue:

                                          Actually, they should. They usually don't as per Amdahl's law. I've a piece I'd written for work that scales almost perfectly with the number of cores, however the task I'd implemented is such that it is extremely parallelizable.

                                          If you use threads on all your processor cores, at least some of them have other tasks to do (OS background services etc.), so you will always lose some msec to a few secs or am I wrong?


                                          If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                                          ~E. W. Dijkstra

                                          kshegunovK 1 Reply Last reply
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