Problem with QtConcurrent::run

[januszmk]

Hello.
I want to have variable number of threads in my application depends of settings.
I am using QtConcurrent::run because then I can run any function of any class.
I did something like this:

QVector<QFuture<void> > asda;
for(i=0; i<n; i++)
{
    asda[i] = QtConcurrent::run(this, &MainWindow::thr1);
}
for(i=0; i<n; i++)
{
    asda[i].waitForFinished();
}

QVector<QFuture<void> > asda;
for(i=0; i<n; i++)
{
    asda[i] = QtConcurrent::run(this, &MainWindow::thr1);
}
for(i=0; i<n; i++)
{
    asda[i].waitForFinished();
}

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but when it is runing MainWindow::thr1 for the second time, then I get aplication error and:

app.exe exited with code -1073741819

app.exe exited with code -1073741819

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my header file:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <mailbox.h>
#include <QStandardItem>
#include <QStandardItemModel>
#include <QtCore>
#include <QFileDialog>
 
 
namespace Ui {
    class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
private slots:
    void on_pushButton_clicked();
    void upd(int numer, int percent, int speed);
 
    void on_pushButton_3_clicked();
 
    void on_pushButton_2_clicked();
 
private:
    QStandardItem *item;
    QStandardItemModel *model;
    Ui::MainWindow *ui;
    std::string generate();
    mailbox *mailb[8];
    void thr1();
    QString dir;
    void download();
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <mailbox.h>
#include <QStandardItem>
#include <QStandardItemModel>
#include <QtCore>
#include <QFileDialog>


namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();
    void upd(int numer, int percent, int speed);

    void on_pushButton_3_clicked();

    void on_pushButton_2_clicked();

private:
    QStandardItem *item;
    QStandardItemModel *model;
    Ui::MainWindow *ui;
    std::string generate();
    mailbox *mailb[8];
    void thr1();
    QString dir;
    void download();
};

#endif // MAINWINDOW_H

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and MainWindow::thr1 function is just for testing:

void MainWindow::thr1()
{
qDebug() << "test";
}

void MainWindow::thr1()
{
qDebug() << "test";
}

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What am I doing wrong?
I would be grateful, if someone could help.
Janusz

[nosleduc]

The asda vector is not correctly initialized, you have to set the size before using the operator[]

[januszmk]

thanks, I replace = with pushback and it is working now. But I have one more question, how can I close the threads when my application is closing, if i don't wait for finished? Because when I am closing application, just window is closing.

[nosleduc]

One possible solution is to add a flag in your class to see if the user wants to quit the application and deals with it directly in your function thr1 to abort the computation.

[januszmk]

thanks for help

[januszmk]

I get one more problem with QtConcurrent::run, When I run this function:

void MainWindow::download()
{
    QItemSelection selection( ui->tableView->selectionModel()->selection() );
    foreach( const QModelIndex & index, selection.indexes() )
    {
       rows.append( index.row() );
    }
    down1 = rows.count();
    if(ui->lineEdit_3->text().isEmpty())
    {
        on_pushButton_3_clicked();
    }
    watek.clear();
    for(down=0; down<8; down++)
    {
        connect(mailb[down], SIGNAL(progress(int,int,int)), this, SLOT(upd(int,int,int)));
        connect(mailb[down], SIGNAL(done(int)), this, SLOT(asda(int)));
        QString temp1 = ui->tableView->model()->data(ui->tableView->model()->index(rows[down],0)).toString();
        QString temp2 = ui->tableView->model()->data(ui->tableView->model()->index(rows[down],1)).toString();
        mailb[down]->number = rows[down];
        mailb[down]->number1 = down;
        QString type = mailb[down]->type.c_str();
        temp1 = ui->lineEdit_3->text() + "/" + temp1;
        qDebug() << temp1 << temp2;
        watek.push_back(QtConcurrent::run(mailb[down], &mailbox::downloadFile, temp2, temp1));
        //mailb[0]->downloadFile(temp2, temp1);
    }
}

void MainWindow::download()
{
    QItemSelection selection( ui->tableView->selectionModel()->selection() );
    foreach( const QModelIndex & index, selection.indexes() )
    {
       rows.append( index.row() );
    }
    down1 = rows.count();
    if(ui->lineEdit_3->text().isEmpty())
    {
        on_pushButton_3_clicked();
    }
    watek.clear();
    for(down=0; down<8; down++)
    {
        connect(mailb[down], SIGNAL(progress(int,int,int)), this, SLOT(upd(int,int,int)));
        connect(mailb[down], SIGNAL(done(int)), this, SLOT(asda(int)));
        QString temp1 = ui->tableView->model()->data(ui->tableView->model()->index(rows[down],0)).toString();
        QString temp2 = ui->tableView->model()->data(ui->tableView->model()->index(rows[down],1)).toString();
        mailb[down]->number = rows[down];
        mailb[down]->number1 = down;
        QString type = mailb[down]->type.c_str();
        temp1 = ui->lineEdit_3->text() + "/" + temp1;
        qDebug() << temp1 << temp2;
        watek.push_back(QtConcurrent::run(mailb[down], &mailbox::downloadFile, temp2, temp1));
        //mailb[0]->downloadFile(temp2, temp1);
    }
}

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function downloadFile is run just twice, not 8 times. Is there maybe some limits for number of threads? If there are, then how can I bypass that limits?

Edit:
I found then QtConcurrent is using QThreadPool and I add "QThreadPool::globalInstance()->setMaxThreadCount(10);" and now it's working