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Ask HN: How would you implement an (accurate) progress bar?
2 points by amelius 67 days ago | hide | past | web | favorite | 4 comments
Progress bars in existing software are often "broken". That is, by observing a progress bar, the user often cannot predict how long an operation will still take. Sometimes, the bar runs to 100% in a matter of seconds, after which processing continues for minutes or hours. In other cases, they hang at a low percentage, and then they suddenly skip to 100%. Similarly, "ETA" indicators are often broken too.

So, how would you implement a progress bar that Just Works (TM)?

Or is the problem so difficult to solve correctly, that it would require a Ph.D. project? In that case, the question is: why has nobody done theoretical work on the subject?

Somewhat related "Using Zeno's Paradox For Progress Bars" [the article is dead, but this is the archived version] https://web.archive.org/web/20140224013525/http://www.atalas...

More in: http://cerealnumber.livejournal.com/27537.html#/27537.html

My favorite progress bar implementation is in Hadoop because Hadoop breaks problems into small chunks that are (almost always) predictable so it can give a good ETA even at a few percent level.

Something I've thought about (but not done) is making something that records the log entries that a build process emits as it runs and then compares the progress of the current run to the historical database.

A progress bar for what? Some things are trivial (copying a local file with a known size), some are impossible (streaming a file of an unknown size). It's not the problem is a progress bar, it's a problem of:

- How reliably can you provide the current stage mapped to the linear progress (do you know what step you're on? Do you know how many store exist / are enabled / are applicable?)

- How reliably can you map each stage to the time required? Does it depend on the environment / hardware / selected configuration?

For many cases the second one is basically unknown. You can still do a combination of lists and progress bars per step, or something similar to make it easier.

Valid questions!

Of course, we should assume that the information which the progress bar needs is "knowable".

And perhaps the question needs better phrasing, because there will be a trade-off between the resources used for computing the progress and it's accuracy.

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