[stackghost]

For control systems like avionics it either passes the suite of tests for certification, or it doesn't. Whether a human could write code that uses less memory is simply not important. In the event the autocode isn't performant enough to run on the box you just spec a faster chip or more memory.

[addaon]

I’m sorry, but I disagree. Building these real-time safety-critical systems is what I do for a living. Once the system is designed and hardware is selected, I agree that if the required tasks fit in the hardware, it’s good to go — there’s no bonus points for leaving memory empty. But the sizing of the system, and even the decomposition of the system to multiple ECUs and the level of integration, depends on how efficient the code is. And there are step functions here — even a decade ago it wasn’t possible to get safety processors with sufficient performance for eVTOL control loops (there’s no “just spec a faster chip”), so the system design needed to deal with lower-ASIL capable hardware and achieve reliability, at the cost of system complexity, at a higher level. Today doing that in a safety processors is possible for hand-written code, but still marginal for autogen code, meaning that if you want to allow for the bloat of code gen you’ll pay for it at the system level.

[stackghost]

>And there are step functions here — even a decade ago it wasn’t possible to get safety processors with sufficient performance for eVTOL control loops (there’s no “just spec a faster chip”)

The idea that processors from the last decade were slower than those available today isn't a novel or interesting revelation.

All that means is that 10 years ago you had to rely on humans to write the code that today can be done more safely with auto generation.

50+ years of off by ones and use after frees should have disabused us of the hubristic notion that humans can write safe code. We demonstrably can't.

In any other problem domain, if our bodies can't do something we use a tool. This is why we invented axes, screwdrivers, and forklifts.

But for some reason in software there are people who, despite all evidence to the contrary, cling to the absurd notion that people can write safe code.

[addaon]

> All that means is that 10 years ago you had to rely on humans to write the code that today can be done more safely with auto generation.

No. It means more than that. There's a cross-product here. On one axis, you have "resources needed", higher for code gen. On another axis, you have "available hardware safety features." If the higher resources needed for code gen pushes you to fewer hardware safety features available at that performance bucket, then you're stuck with a more complex safety concept, pushing the overall system complexity up. The choice isn't "code gen, with corresponding hopefully better tool safety, and more hardware cost" vs. "hand written code, with human-written bugs that need to be mitigated by test processes, and less hardware cost." It's "code gen, better tool safety, more system complexity, much much larger test matrix for fault injection" vs "human-written code, human-written bugs, but an overall much simpler system." And while it is possible to discuss systems that are so simple that safety processors can be used either way, or systems so complex that non-safety processors must be used either way... in my experience, there are real, interesting, and relevant systems over the past decade that are right on the edge.

It's also worth saying that for high-criticality avionics built to DAL B or DAL A via DO-178, the incidence of bugs found in the wild is very, very low. That's accomplished by spending outrageous time (money) on testing, but it's achievable -- defects in real-world avionics systems overwhelming are defects in the requirement specifications, not in the implementation, hand-written or not.

[stackghost]

HN is a very poor platform for good conversations so we'll have to agree to disagree, as I'm not willing to go further in this format

[menaerus]

Codegen from Matlab/Simulink/whatever is good for proof of concept design. It largely helps engineers who are not very good with coding to hypothesize about different algorithmic approaches. Engineers who actually implement that algorithm in a system that will be deployed are coming from a different group with different domain expertise.