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

there is no standard algorithm i know of, my sugestion would be:

• Create a variable to save the %
• Calculate the complexity of the task you wish to track(or an estimative of it)
• Put increments to the % from time to time as you would see fit given the complexity.

You probably seen programs where the load bar runs much faster in one point than in another. Well that's pretty much because this is how they do it. (though they probably just put increments at regular intervals in the main wrapper)

Answer 2

There is 2 ways of showing time

1. Time elapsed and Time Remaining overall: so elapsed will increase but remaining will be likely stable total time needed (if per second is stable)

2. Time elapsed and Time Left:
   so Time Left = Total Needed - Elapsed

My idea/formula is more likely like this:

Processed - updated from running thread from 0 to Total

I have timer with 1000ms interval that calculates processed per second:

processedPerSecond = Processed - lastTickProcessed;
lastTickProcessed = Processed;  //store state from past call

processedPerSecond and lastTickProcessed are global variables out of timer method

Now if we would like to get how many seconds is required to complete the processing (in ideal constant assumption) totalSecondsNeeded = TotalLines / PerSecond

but we want to show case 2. TimeLeft so TimeLeftSeconds = (TotalLines - Processed) / PerSecond

TimeSpan remaining = new TimeSpan(0, 0, (transactions.Count - Processed) / processedPerSecond);
labelTimeRemaining.Text = remaining.ToString(@"hh\:mm\:ss");

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Of course TimeLeftSeconds will "jump" if PerSecond jumps, so if past PerSecond was 10 then 30 then back to 10, the user will see it.

There is a way to calculate average, but this may not show real time left if process speeds up at the end

int perSecond = (int)Math.Ceiling((processed / (decimal)timeElapsed.TotalSeconds));  //average not in past second

So it may be the choice for a developer to "pick" a method that will be most accurate based on prediction of how "jumpy" the processing is

We could also calculate and save each PerSecond, then take last 10 second and made average, but in this case user will have to wait 10 seconds to see first calculation or we could show time left starting from first per second and then progressively average summing up to 10 last PerSecond

I hope my "jumpy" thoughts will help someone to build something satisfying

Answer 3

It depends greatly on what the "something" is. If you can assume that the amount of time to process each line is similar, you can do a simple calculation:

TimePerLine = Elapsed / LinesProcessed
TotalTime = TimePerLine * TotalLines
TimeRemaining = TotalTime - LinesRemaining * TimePerLine

Answer 4

Make sure to manage perceived performance.

Although all the progress bars took exactly the same amount of time in the test, two characteristics made users think the process was faster, even if it wasn't:

1. progress bars that moved smoothly towards completion
2. progress bars that sped up towards the end

Answer 5

Not to revive a dead question but I kept coming back to reference this page.
You could create an extension method on the Stopwatch class to get functionality that would get an estimated remaining time span.

static class StopWatchUtils
{
    /// <summary>
    /// Gets estimated time on compleation. 
    /// </summary>
    /// <param name="sw"></param>
    /// <param name="counter"></param>
    /// <param name="counterGoal"></param>
    /// <returns></returns>
    public static TimeSpan GetEta(this Stopwatch sw, int counter, int counterGoal)
    {
        /* this is based off of:
         * (TimeTaken / linesProcessed) * linesLeft=timeLeft
         * so we have
         * (10/100) * 200 = 20 Seconds now 10 seconds go past
         * (20/100) * 200 = 40 Seconds left now 10 more seconds and we process 100 more lines
         * (30/200) * 100 = 15 Seconds and now we all see why the copy file dialog jumps from 3 hours to 30 minutes :-)
         * 
         * pulled from http://stackoverflow.com/questions/473355/calculate-time-remaining/473369#473369
         */
        if (counter == 0) return TimeSpan.Zero;
        float elapsedMin = ((float)sw.ElapsedMilliseconds / 1000) / 60;
        float minLeft = (elapsedMin / counter) * (counterGoal - counter); //see comment a
        TimeSpan ret = TimeSpan.FromMinutes(minLeft);
        return ret;
    }
}

Example:

int y = 500;
Stopwatch sw = new Stopwatch();
sw.Start();
for(int x = 0 ; x < y ; x++ )
{
    //do something
    Console.WriteLine("{0} time remaining",sw.GetEta(x,y).ToString());
}

Hopefully it will be of some use to somebody.

EDIT: It should be noted this is most accurate when each loop takes the same amount of time.
Edit 2: Instead of subclassing I created an extension method.

Answer 6

Where time$("ms") represents the current time in milliseconds since 00:00:00.00, and lof represents the total lines to process, and x represents the current line:

if Ln>0 then
    Tn=Tn+time$("ms")-Ln   'grand total of all laps
    Rn=Tn*(lof-x)/x^2      'estimated time remaining in seconds
end if
Ln=time$("ms")             'start lap time (current time)