I’ve said this previously but I don’t agree that software estimating is possible in theory. It’s a form of the halting problem. You can’t, even in theory, know how long something will take until you do it.

It’s certainly possible to estimate to a rough-order-of-magnitude but the problem is that the ROM quickly becomes a target, and then a commitment.

I have a couple of positions that I take.

First, the old adage still applies: “better, faster, cheaper - choose two”. If you set a deadline then you have to be willing to drop features or quality, because Brooks already demonstrated you can’t add resources after you start.

Second, if you do need to set a deadline then prioritise it, stick to it and celebrate it. Too many times deadlines are used as a whip, and my or my team have wiped themselves out to meet it, only to be told it wasn’t really needed. This is insanely demoralising and strongly affects productivity in the long term.

My personal (and unpopular) preference is to prioritise completion of stand-alone features rather than building to deadlines, which means you can release a product at almost any time with fewer, but better quality features. This approach has a demonstrable positive impact on the ROI but because it’s more complex and provides less short term certainty, it’s frowned upon.

I think in pure compsci theory you might be right, but in practice (industrial SW production), we usually limit ourselves to algorithmic solutions that do not involve halting problem, so estimation is possible. For example, an upper limit for a rewrite of a system is how long it took to create the original system (provided you understand the tradeoffs and issues of the original architecture).

I don’t understand. The halting problem says you can’t tell if an algorithm halts without running it - you can’t be sure any program will run to completion in a specific time. It applies to any non trivial program.

And it’s well established that a rewrite is dangerous. The second system effect suggests that rewrites will always take much longer.