[milancurcic]

Fortran predictably overflows the result, in contrast to fptoui which gives a poison value. I agree that even a predictable overflow can bite you on the behind. But it's better than undefined behavior. I'm not a fan of saturated cast, but having a defined behavior is for sure a great improvement.

[nitrogen]

When working with audio as an example, saturation is much less obnoxious than wraparound. You can potentially destroy speakers and your hearing that way.

[pjmlp]

Wraparound is also the bug that turns Ghandi into a huge dictator in Civilization, and killed a couple of people in cancer treatment devices.

[nindalf]

For those not in the know, computer controlled Civs would be assigned behaviour attributes based on historical personality. Each attribute would be 1-10, stored in an 8 bit integer.

These attributes change in response to events in the game. When a civilization would reach the modern era, it's aggression attribute would be reduced by 2. Gandhi's aggression was reduced from 1 to 255 (underflow). He would rain down nukes on everything in sight, somewhat uncharacteristic of him.

Fans liked this so much that Firaxis maintained the same behaviour in later games.

[paavohtl]

It's a cool story, but I don't think there is evidence that it actually happened (in Civ 1, certainly in later games as a homage to this potentially urban legend). The YouTube channel People Make Games did an investigation[1] about this a year ago, including interviews with the original developers.

[1] https://www.youtube.com/watch?v=Ur3SdgkW8W4

[nindalf]

TIL that I am fake news.

[tialaramex]

Saturated addition is indeed the correct way to add two PCM streams together.

Especially back in the 1980s and 1990s you'd get awful code that did things like averaging the two streams because wrapping sounds awful and the authors were ignorant of the theory and/or unaware that saturated addition is a thing.

You can tell when somebody did this because it means playing silence makes everything else quieter, or worse there's an arbitrary limit on how many streams are played and playing any one thing is very quiet because it's attenuated so as to never wrap.

Haiku the 1990s-style operating system did this for years, as did various Amiga music software.

[diffuse_l]

At least on x86, saturated adds didn't become a thing until MMX was released. Doing saturated adds was simply too expensive on older machines, and usually required a branch.

[sjwright]

Why would you want math errors to be less obnoxious?

[frabert]

They're not math errors, it's the most sensible thing to do: when you overload a speaker, you get clipping, not some weird thing where the cone snaps to the opposite side of the range.

[sjwright]

I’m talking about the basis of the analogy, not the analogy. If you’re processing audio signals, saturation (i.e. clipping) is of course preferable to the alternative.

[baseballdork]

I think they just prefer them to be less destructive.

[sjwright]

“Destructive”, regardless how minor, should be intentional or at the very least conscious. This is one of the various reasons why serious audio processing is done as 32 bit float: no (practical) risk of unexpected overflows.

[jabl]

> Fortran predictably overflows the result

Not sure what you mean here, and I don't have the standard at hand ATM, but I'm quite sure this is undefined behaviour in Fortran.

But yes, I agree defined behaviour is good. Undefined behaviour is occasionally good for optimization, at the cost of gray hairs for users.

[milancurcic]

Standard? True, undefined. Compilers, however, happily overflow unless you tell them to catch it at run time. So, my original statement is at least half false. :)