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Comment by charles_irl | Hacker News Reader

Hey, one of the authors here!

Reductively, software engineering means taking an idea and mapping it into code. So one form of "reverse" engineering would be taking the code and extracting the ideas. That's what we did here.

Because the source is public, there's quite a lot to work with from the start -- the warp specializations are named and there are helpful comments in many places.

But for many components, we didn't have much. Maybe the clearest case of "reverse engineering" explained in the post is with the cubic approximation for the rational part of the exponentiation. That required staring at some inline assembly and doing math.

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I've never heard of this definition of reverse engineering -- when one has the unobfuscated actual source code I'd usually call it: reading the code, or something like summarization.

Not trying to be uncharitable, I found your article informative. Reverse engineering has historically been reserved for cases where there is an adversial aspect, as in binaries or server APIs. Anyhow, Cheers and thank you, sincerely.

That time when I reverse engineered JRR Tolkien‘s Lord of the rings from symbols engraved on dead trees. Took me three summers…

Having the source code and understanding how it works is two different things, especially when running on state of the art hardware. If I had just read the source I would not have gained as much knowledge as this article taught me. Where did this extra info come from? They read the source too, but then they did something more. I wouldn’t call it summarization either, as again any summary I wrote about the code would pale in comparison.

I think "explained" is a reasonable term for this. If I remember correctly there where books of the form "The Linux Source Code Explained".

Certainly I can't get on board with reverse engineered.

You've never had to reverse engineer the thinking and ideas that went behind code written by someone else/you a year ago?

No, because so far you "engineered" nothing. You just studied it, tried to understand it, and explain or teach it.

If you had reverse engineered it, you would have tried to "recreate something" that does not exist to do the same.

So, if you have a binary code, you recreate the source code that in theory could allow you to recreate the binary.

If you have the source code, I guess that would be when you are missing pieces of info that allows you to run this code like it is done by others...

You guys are being obtuse. Engineering is turning a spec into a more technical artifact, whether that's source code, machine code, physical hardware or something else. Reverse engineering is then reserving the process of engineering, recovering the semantic artifact from the engineering artifact. That the OP is using the term in the sense of recovering the semantic insights from the cuda kernels is a fine application of the concept.

Disagree that reverse engineering necessarily requires something to be recreated.

For example, simple hardware reversing can just be learning what, how and why something works, you don't need to "recreate" anything other than ideas.

That is the traditional explanation of why it is called reverse engineering. The term originated in hardware engineering. When it was originally applied to software, it was common to create requirements documents and design documents before coding, even if the actual process did not strictly follow the "waterfall" idea.

Thus it was natural to call the process of producing design documents from undocumented software "reverse engineering". These days coding without any formal design documents is so common that it seems the original meaning of reverse engineering has become obscured.

What time period and area did you come across this usage? As I ever saw it used, 'reverse engineering' generally referred to creating docs from executables or watching network protocols rather than from source.

Back in the 1990's. As an example, back then the Rational Rose design software had a feature to generate UML diagrams from existing source code, and it was called "reverse engineering".

https://en.wikipedia.org/wiki/IBM_Rational_Rose

it’s more properly just software archaeology; recovering design intent from artifacts https://en.m.wikipedia.org/wiki/Software_archaeology

I have to say this is kind of funny given that you also had this in the blog post:

> cudnn kernels are closed source, so Jensen only knows what’s going on in there.

It's the 'hacker' argument all over again.

I reverse engineered above comment by reading it and extracting the idea.

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