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Comment by hparadiz | Hacker News Reader

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Sorry, I'm too busy trying to check an algorithm to convert floating-point numbers to strings for correctness to deal with people playing the "I'm a rocket scientist, therefore everything is easy to me" card. And yet somehow Elon isn't that (see his most recent SpaceX, where he quite literally uses that to justify his competence to build orbital data centers).

I implemented float-to-string for my compiler's printf back sometime before 1985. It's a medium difficult problem.

Once you understand engineering, transferring that skill to another engineering discipline is not that hard.

For example, the equations for Newtonian mechanics, electronics, beam design, rotating inertia, etc., are interchangeable.

> his competence to build orbital data centers

Since nobody has yet built an orbital data center, nobody is competent at it yet.

> I implemented float-to-string for my compiler's printf back sometime before 1985. It's a medium difficult problem.

It might have been medium difficult back in 1985, but the state of the art has progressed in the intervening 40 years. The constraint of correctness makes things trickier because it further imposes three requirements: completeness, uniqueness, and determinism.

Unless the implementer has the skill to prove these properties about the algorithm they've implemented, such an implementation is likely not to achieve those requirements.

There was no test suite for it available that I could use for correctness checks, so I did what I could.

I also implemented IEEE 754 floating point in asm. For that I did have an exhaustive test suite, and passed it 100%.

We didn't have this definition of correctness until 1990 (due to Steele and White), and it wasn't until the past decade or so that we got a published algorithm (most recently, I think, Dragonbox, due to Jeon when he was still working on his PhD at UCSD), with mathematical proof[0], that satisfied all of the requirements of being complete, being unique, and being deterministic.

(Though, Steele-White expresses these slightly differently, as preserving information, having the shortest possible output, and rounding correctly. Completeness, uniqueness, and determinism seem to be equivalent and are easier to prove.)

0: Available at <https://fmt.dev/papers/Dragonbox.pdf>. It's pretty easy to understand either with a numerical analysis background or after having worked through volume 2 of Knuth's TAoCP.

I didn't know that! Thanks for the link to the paper. I've saved it for later reading!

What an odd comment. You think because he is the CEO of a rocket company that naturally he is beyond making stuff up and talking BS? Have you ever watched an interview of his?

And why are CEOs as smart as engineers now.

This isn't Twitter. You don't have to suck up to him. He won't ever see this.

You are the odd comment. It's been like this my entire life. I was like 20 when Elon was near bankruptcy when Tesla was basically nothing. Then I watched him found SpaceX and again almost run out of money. I then watched him make electric cars a reality from nothing. I then watched him turn the space industry completely upside down. You think elons a bad guy? Whatever. You lost your moral high ground as soon as you started lying. I've watched him give hundreds of interviews with off the cuff engineering specifics. I don't care if he sees this or not. Tired of humoring morons. This isn't reddit. You don't have to suck up to the commies.

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