Question

In short, I’m utilizing C# to scientific computation and I’ve written a method that has a while loop that may run to a user-specified quantity of steps… Actually, this method may take too long to execute (like more than 5 hours). When it takes this long, I may want to stop the method pressing Esc key, for example.

As I read something about breaking while, it is as simple as a Boolean flag or something like this. So I thought in something like this:

public Double? Run(int n)
{
    int i = 0;
    while ((i < n) && (/* inputkey != ConsoleKey.Escape */))
    {
        // here goes the heavy computation thing
        // and I need to read some "inputkey" as well to break this loop
        i++;
    }
    // I'm not worried about the return statement, as it is easy to do...
    // returns null if the user skipped the method by pressing Escape
    // returns null if the method didn't converged
    // returns the double value that the method calculated otherwise
}

Well, this is what I wondered until now… So please, could you give useful ideas to this extent? How can I wait for a user input (I thought about Events, but I’m not sure how to implement it here and I think that it will make the code even slower, if I have to listen to a key at every while step the code goes into…

Well, any ideas or comments?

---

Update: I think I should have had described better the problem. All the solutions you gave me may solve this problem I proposed, but I think I was not completely reliable to my real problem. I don’t know if I should ask another question or keep with this one…

Answer 1

You could run this method from a separate thread and set a stop variable when a key is pressed:

object myLock = new object();
bool stopProcessing = false;

public Double? Run(int n)
{
    int i = 0;
    while (i < n)
    {
        lock(myLock)
        {
            if(stopProcessing)
                break;
        }
        // here goes the heavy computation thing
        // and I need to read some "inputkey" as well to break this loop
        i++;
    }
}

and when a key is pressed, update stopProcessing accordingly:

Console.ReadKey();
lock(myLock)
{
    stopProcessing = true;
}