How to stop QFuture thread

Ketan__Patel__0011

Hello experts

i was create a small threading application , in this application one function is run parallelly

i am using QFuture and QConcurrent

my problem in when i try to stop qfuture that time it can't be stop

my code is :

                    void Mainwindow::Function_1()                        
                    {                        
                        for(int i=1 ; i <= 10 ;i++)                        
                        {                                        
                            QThread::sleep(1);                        
                            ui->label->setText(QString::number(i));                        
                        }                       
                    }

                   ////////////// Start ////////////
                   void Mainwindow::on_start_Button_clicked()                       
                   {                                 
                       future_1 = QtConcurrent::run(this,&Mainwindow::Function_1);                       
                   }
                  ////////////// Stop////////////
                  void Mainwindow::on_stop_Button_clicked()                      
                  {                                       
                      if(this->future_1.isRunning())                      
                      {                      
                          this->future_1.cancel();                      
                          this->future_1.setPaused(true);                                   
                      }                      
                  }

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

i read some documentation online but i can't get solution

i am not able to stop qfuture thread between the running process
please Help me to solve this problem

Thanks in advance

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Bonnie

QFurture cannot stop untill the fuction is completely executed...

Be aware that not all running asynchronous computations can be canceled. For example, the future returned by QtConcurrent::run() cannot be canceled;

QFuture::cancel() does not stop the thread immediately, it just cancels all the unstarted jobs.

Ketan__Patel__0011

@Bonnie
thanks for the replay

but any how i want to stop it

is it have any other way to stop any process when it is running ?

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
please help me to solve the problem
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Bonnie

@Ketan__Patel__0011

You can considering doing the normal way to stop a loop in another thread: adding a member variable to control the loop.

bool b_exitloop = false;

for(int i=1 ; i <= 10 && !b_exitloop;i++)                        
{
    QThread::sleep(1);
    ui->label->setText(QString::number(i));
}

if(this->future_1.isRunning())
{
  this->b_exitloop  = true;
  this->future_1.waitForFinished();
  this->b_exitloop = false;
}

But this cannot stop the sleep.
Also be careful about synchronizing threads if you need to.

Ketan__Patel__0011

@Bonnie

Thanks for reply

i also try this way and i get good result

but this is not a proper and good way for any large application and sensitive application

i need a proper way to solve this problem

i am also doing research for this

Bonnie

@Ketan__Patel__0011 Well, another way is to not using loop in you function and not using run. Try using those map functions in QtConcurrent.
Then you can cancel it.

Ketan__Patel__0011

@Bonnie
thanks for reply

without looping statements is not reliable to manage lot's of process
sorry but i can't remove looping statements

Bonnie

Then I think QtConcurrent is not the right solution for you when you need to exit a loop.
The only way to exit a loop is still controlling by a variable.

Ketan__Patel__0011

@Bonnie

Let's suppose if i use variable for controlling then when i false the any variable or boolean flag that time
is memory still consuming or not ?

Bonnie

What memory do you mean?

Ketan__Patel__0011

@Bonnie

if i stop the any function process using any boolean flag

that time is memory(RAM) are still consuming or not ?

and CPU are still used ?

Bonnie

If you exit the loop, the code in the loop will stop being executed.
I don't understand what memeory / CPU are you talking about.