Question

What is the most efficient way to create a “cancel” event in a C# program that is crunching a large set of data in a loop on a separate thread?

For now, I am simply using a cancel event that is triggered from my UI thread, which subsequently calls an “onCancel” function on the number crunching thread. That cancel function sets a variable to “true”, which the crunch loop checks periodically, e.g.

Class Cruncher {  
    private bool cancel = false;

    public cruncher()
    {
        crunch();
    }

    private void crunch()  
    {   
        while(conditions AND !cancel) { crunch; }

        dispose_resources;
    }

    private void onCancel() 
    { 
        cancel = true;
    }
}

While I am not checking the cancel variable as often as my example above (and not actually performing a NOT cancel), I would still like to optimize this crunch method as much as possible. Any examples where this is done more efficiently would be very nice to see.

Answer 1

The cancel event/flag should be a volatile… I asked a very similar question to yours: Is it safe to use a boolean flag to stop a thread from running in C#

I would also recommend that when you cancel your threads you wait for all of them to cancel by using something similar to the C# version of CountDownLatch. It’s useful when you want to guarantee that the thread is canceled.