How to accelerate the loop speed ?

[wshn13]

Hi ,all:
I am working on a small program .This program is to show info on a QTableWidget , it may have thousand rows , but the main time waste section is a loop , code like below :

int i=0;
  vector<Case>::iterator it = tmp.begin();
  for(;it!=tmp.end();it++, i++)
  {
       table->insertRow(i);
       table->setCellWidget( i, 0, new QCheckBox(QString("Y/N")));
       table->setItem(i, 1, new QTableWidgetItem(((*it).type)));
       table->setItem(i, 2, new QTableWidgetItem(QString((*it).name.c_str())));
       table->setItem(i, 3, new QTableWidgetItem(QString((*it).note.c_str())));
  }

int i=0;
  vector<Case>::iterator it = tmp.begin();
  for(;it!=tmp.end();it++, i++)
  {
       table->insertRow(i);
       table->setCellWidget( i, 0, new QCheckBox(QString("Y/N")));
       table->setItem(i, 1, new QTableWidgetItem(((*it).type)));
       table->setItem(i, 2, new QTableWidgetItem(QString((*it).name.c_str())));
       table->setItem(i, 3, new QTableWidgetItem(QString((*it).note.c_str())));
  }

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If I delete the line "table->setCellWidget( i, 0, new QCheckBox(QString("Y/N")));" ,the program will go much more faster ,so that line take the most of the loop run time .What should I do to make the program go faster ?

---

Added after 18 minutes:

I need some suggestions

[ChrisW67]

Don't. Thousands of widgets in a table will not be fast to use, even if you make them faster to create.

QTableWidgetItem supports a check box without the overhead of a widget. Try adapting this:

QTableWidget *table = new QTableWidget(1000, 4);
    for(int i = 0; i < 1000; ++i) 
    {
        QTableWidgetItem *item = new QTableWidgetItem("Y/N");
        item->setCheckState(Qt::Unchecked);
        table->setItem(i, 0, item);
        table->setItem(i, 1, new QTableWidgetItem("A"));
        table->setItem(i, 2, new QTableWidgetItem("B"));
        table->setItem(i, 3, new QTableWidgetItem("C"));
    }

QTableWidget *table = new QTableWidget(1000, 4);
    for(int i = 0; i < 1000; ++i) 
    {
        QTableWidgetItem *item = new QTableWidgetItem("Y/N");
        item->setCheckState(Qt::Unchecked);
        table->setItem(i, 0, item);
        table->setItem(i, 1, new QTableWidgetItem("A"));
        table->setItem(i, 2, new QTableWidgetItem("B"));
        table->setItem(i, 3, new QTableWidgetItem("C"));
    }

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[wshn13]

Don't. Thousands of widgets in a table will not be fast to use, even if you make them faster to create.

QTableWidgetItem supports a check box without the overhead of a widget. Try adapting this:

QTableWidget *table = new QTableWidget(1000, 4);
    for(int i = 0; i < 1000; ++i) 
    {
        QTableWidgetItem *item = new QTableWidgetItem("Y/N");
        item->setCheckState(Qt::Unchecked);
        table->setItem(i, 0, item);
        table->setItem(i, 1, new QTableWidgetItem("A"));
        table->setItem(i, 2, new QTableWidgetItem("B"));
        table->setItem(i, 3, new QTableWidgetItem("C"));
    }

QTableWidget *table = new QTableWidget(1000, 4);
    for(int i = 0; i < 1000; ++i) 
    {
        QTableWidgetItem *item = new QTableWidgetItem("Y/N");
        item->setCheckState(Qt::Unchecked);
        table->setItem(i, 0, item);
        table->setItem(i, 1, new QTableWidgetItem("A"));
        table->setItem(i, 2, new QTableWidgetItem("B"));
        table->setItem(i, 3, new QTableWidgetItem("C"));
    }

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I change code like your advice ,but it work the same . Will QTableView have influence ? Do you have any idea ,thanks!

[ChrisW67]

It takes literally 15 milliseconds to execute the loop and create the 4000 items in my example.
Post a complete example program that demonstrates the problem.

BTW: You can resize the table widget once to match the item count of the vector rather than increase it row at a time: QTableWidget::setRowCount().

[wshn13]

I redo it ,it works ! thanks!