[theodorethomas]

The only reason you would want bit-reproducibility is because you haven't done the numerical analysis and have no clue how many digits of your "answer" to trust.

As far as I know, two sectors claim they need it: finance and climate.

"Do you want a better answer?"

"No, I want the same wrong answer that I got last Tuesday."

Science/Mathematics can't fix this.

[MauranKilom]

> The only reason you would want bit-reproducibility is because you haven't done the numerical analysis and have no clue how many digits of your "answer" to trust.

I can confidently say that this is not the only good reason. Other reasons include:

- You want to compare different runs by hashing outputs (e.g. to find the first computation step where they diverged). Very useful for debugging, and also useful to determine whether you accurately reproduced a result (e.g. a customer problem).

- If your program has a single floating point comparison, there is no such thing as "enough significant digits" - with reasonable assumptions about the distribution of "unreproducability", your logic is now divergent (and your output will jump between different values) with a certain probability. At that point we're no longer talking numerical analysis, it's straight up "divergent results".

[owlbite]

There's also "cover your ass". At least I've heard tales of major aerospace companies keeping warehouses of old sun hardware in case they need to demonstrate the simulations they ran back in the 90s were not fabricated...

[thebooktocome]

I’ve yet to meet a customer that cares enough to pay for the necessary numerical analysis.