Calculate Time Remaining

Question

What\'s a good algorithm for determining the remaining time for something to complete? I know how many total lines there are, and how many have completed already, how shoul

Answer 1

I prefer System.Threading.Timer rather than System.Diagnostics.Stopwatch.

System.Threading.Timer, which executes a single callback method on a thread pool thread

The following code is an example of a calculating elapsed time with Threading.Timer.

public class ElapsedTimeCalculator : IDisposable
{
    private const int ValueToInstantFire = 0;

    private readonly Timer timer;
    private readonly DateTime initialTime;

    public ElapsedTimeCalculator(Action action)
    {
        timer = new Timer(new TimerCallback(_ => action(ElapsedTime)));
        initialTime = DateTime.UtcNow;
    }

    // Use Timeout.Infinite if you don't want to set period time.
    public void Fire() => timer.Change(ValueToInstantFire, Timeout.Infinite);

    public void Dispose() => timer?.Dispose();

    private TimeSpan ElapsedTime => DateTime.UtcNow - initialTime;
}

BTW You can use System.Reactive.Concurrency.IScheduler (scheduler.Now.UtcDateTime) instead of using DateTime directly, if you would like to mock and virtualize the datetime for unit tests.

public class PercentageViewModel : IDisposable
{
    private readonly ElapsedTimeCalculator elapsedTimeCalculator;

    public PercentageViewModel()
    {
       elapsedTimeCalculator = new ElapsedTimeCalculator(CalculateTimeRemaining))
    }

    // Use it where You would like to estimate time remaining.
    public void UpdatePercentage(double percent)
    {
        Percent = percent;
        elapsedTimeCalculator.Fire();
    }

    private void CalculateTimeRemaining(TimeSpan timeElapsed)
    {
        var timeRemainingInSecond = GetTimePerPercentage(timeElapsed.TotalSeconds) * GetRemainingPercentage;

        //Work with calculated time...  
    }

    public double Percent { get; set; }

    public void Dispose() => elapsedTimeCalculator.Dispose();

    private double GetTimePerPercentage(double elapsedTime) => elapsedTime / Percent;

    private double GetRemainingPercentage => 100 - Percent; 
}