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

app.exe exited with code -1073741819
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

and MainWindow::thr1 function is just for testing:

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