Smart progress bar ETA computation

Question

In many applications, we have some progress bar for a file download, for a compression task, for a search, etc. We all often use progress bars to let users know something is

Answer 1

I have tried and simplified your "easy"/"wrong"/"OK" formula and it works best for me:

t / p - t

In Python:

>>> done=0.3; duration=10; "time left: %i" % (duration / done - duration)
'time left: 23'

That saves one op compared to (dur*(1-done)/done). And, in the edge case you describe, possibly ignoring the dialog for 30 minutes extra hardly matters after waiting all night.

Comparing this simple method to the one used by Transmission, I found it to be up to 72% more accurate.