Rosetta 2 creator leaves Apple to work on Lean full-time

Lean is a currently-niche programming language / proof-assistant. A proof assistant is basically a tool to construct mathematical proofs, which verifies that the proofs are correct like how a compiler verifies types in your programs.

IIUC a regular programming language with a certain set of restrictions already duals as a proof-assistant as discovered by Curry & Howard. By restrictions, I mean something like how Rust forces you to follow certain rules compared to Java.

cwzwarich10• 2 years ago

This is me! Didn’t expect to see this on here, but I’m looking forward to working with everyone else at the Lean FRO and the wider Lean community to help make Lean even better.

My background is in mathematics and I’ve had an interest in interactive theorem provers since before I was ever a professional software engineer, so it’s a bit of a dream come true to be able to pursue this full-time.

brcmthrowaway2• 2 years ago

Surprised you didnt go into something AI adjacent

adamnemecek2• 2 years ago

Lean is AI adjacent.

fantod• 2 years ago

I don't know what his reasons are but it makes sense to me. Yes, there are incredible results coming out of the AI world but the methods aren't necessarily that interesting (i.e. intellectually stimulating) and it can be frustrating working in a field with this much noise.

oulipo• 2 years ago

This is *VERY* AI-adjacent... the next batch of AI algos will need to integrate reasoning through theorem provers to go next level

adamnemecek2• 2 years ago

What was the tipping point that made you want to work on Lean?

cwzwarich10• 2 years ago

I don't think there was a single tipping point, just a growing accumulation of factors:

- the release of Lean 4 slightly over a year ago, which impressed me both as a proof assistant and a programming language

- the rapid progress in formalization of mathematics from 2017 onward, almost all of which was happening in Lean

- the growing relevance of formal reasoning in the wake of improvements in AI

- seeing Lean's potential (a lot of which is not yet realized) for SW verification (especially of SW itself written in Lean)

- the establishment of the Lean FRO at the right time, intersecting all of the above

croemer7• 2 years ago

We're you really _the_ creator of Rosetta 2? How big was the team, what was your role in it?

Rosetta 2 is amazing, I'm genuinely surprised this is the work of just one person!

cwzwarich10• 2 years ago

I was the only person working on it for ~2 years, and I wrote the majority of the code in the first version that shipped. That said, I’m definitely glad that I eventually found someone else (and later a whole team) to work on it with me, and it wouldn’t have been as successful without that.

When people think of a binary translator, they usually just think of the ISA aspects, as opposed to the complicated interactions with the OS etc. that can consume just as much (or even more) engineering effort overall.

spockz2• 2 years ago

It is my experience that it is easier to create good quality things as an individual than as a team. Especially for the core of a product. Also look at Asahi.

However, to really finish/polish a product you need a larger group of people. To get the UI just right, to get the documentation right, to advocate the product, to support it.

It is easily possible to have 10 people working on the team and only having a single core person. Then find someone to act as product manager while as the core person you can focus on the core of the product while still setting the direction without having to chase all the other work.

It is possible, but not easy to set up in most organisations. You need a lot of individual credit/authority and/or the business case needs to be very evident.

steego• 2 years ago

This is exciting!

Given your experience with Rosetta 2 and your deep understanding of code translation and optimization, what specific areas in Lean’s code generation pipeline do you see as ‘low-hanging fruit’ for improvement?

Additionally, which unique features or capabilities of Lean do you find most promising or exciting to leverage in pushing the boundaries of efficient and high-quality code generation?

cookiengineer• 2 years ago

Do you have book recommendations in regards to disassembly, syscalls, x86/64 assembler etc?

What do I need to know to be able to build something as advanced as rosetta?

I am assuming that you reimplemented the syscalls for each host/guest system as a reliable abstraction layer to test against. But so many things are way beyond my level of understanding.

Did you build your own assembler debugger? What kind of tools did you use along the way? Were reversing tools useful at all (like ghidra, binaryninja etc)?

peterkelly• 2 years ago

"Virtual Machines: Versatile Platforms for Systems and Processes" by Jim Smith and Ravi Nair is a great book on the topic.

singularity2001• 2 years ago

sorry to hijack the discussion but do you see any chance of consolidating the theoretical framework of real numbers with practical calculations of floats? That is if I proof the correctness of some theorem for real numbers ideally I would just use that as the algorithm to compute things with floats.

also I was shocked to learn that the simple general comparison of (the equality of) two real numbers is not decidable, which is very logical if you think about it but an enormous hindrance for practical applications. Is there any work around for that?

zozbot2342• 2 years ago

You can use floats to accelerate interval arithmetic (which is "exact" in the sense of constructive real numbers) but that requires setting the correct rounding modes, and being aware of quirks in existing hardware floating point implementations, some of which may e.g. introduce non-exact outputs in several of the least significant digits, or even flush "small" (for unclear definitions of "small", not always restricted to FP-denormal numbers) results to zero.

Equality is not computable in the general case, but apartness can be stated exactly. For some practical cases, one may also be able to prove that two real numbers are indeed equal.

markus_zhang13• 2 years ago

Thank you! My work laptop is a M4 Macbook Pro so I really appreciate the beauty of Rosetta. Thank you for the effort!

I just checked your LinkedIn and realized you joined Apple since 2009 (with one year of detour to Mozilla). You also graduated from Waterloo as a Pure Math Graduate student (I absolutely love Waterloo, the best Math/CS school IMO in my country - at the age of 40+ I'd go without doubt if they accept me).

May I ask, what is the path that leads you to the Rosetta 2 project? I even checked your graduate paper: ( https://uwspace.uwaterloo.ca/items/4bc518ca-a846-43ce-92f0-8... ), but it doesn't look like it's related to compiler theory.

(I myself studied Mathematics back in the day, but I was not a good student and I studied Statistics, which I joked that was NOT part of Mathematics, so I didn't take any serious Algebra classes and understand nothing of your paper)

flkenosad• 2 years ago

Waterloo really is the best CS school in the world.

cwzwarich10• 2 years ago

May I ask, what is the path that leads you to the Rosetta 2 project?

The member of senior management who was best poised to suggest who should work on it already knew me and thought I would be the best choice. Getting opportunities in large companies is a combination of nurturing relationships and luck.

mattgreenrocks• 2 years ago

Rosetta 2 is easily one of the most technically impressive things I've seen in my life. I've done some fairly intense work applying binary translation (DynamoRIO) and Rosetta 2 still feels totally magical to me.

cwzwarich10• 2 years ago

Thanks. It means a lot coming from someone with experience in our niche field.

lenkite• 2 years ago

Can Lean can do what TLA+ does - model check thorny concurrency problems ?

yieldcrv• 2 years ago

Out of curiosity, if you’ve been at a FAANG since at least 2009, have you ever retired or taken a “sabbatical” for a year or two, since you would have made enough money to retire and live passively at amounts similar to annual compensation and taxed way better

Just curious how the decisions have formed, its totally fine if FAANG or specifically Apple was fulfilling for you, I also wonder if its financial fear to an irrational extent just because I see that on Blind a lot

cwzwarich10• 2 years ago

I did go to Mozilla Research to work on Servo/Rust for a bit in 2015, which didn’t turn out to be the best decision.

I always assumed that I would stick around at Apple until some singular event that would motivate me to quit, and that would be it. I have been so lucky at Apple to have been in the right place at the right time for several projects: relatively early iPhone team, original iPad team, involved in the GCC -> Clang transition, involved in the 64-bit ARM transition, involved in early Apple Watch development, first engineer working full-time on the Apple silicon transition for the Mac, etc. Obviously I was doing something right if I kept getting these chances, but if I went to another FAANG I wouldn’t have the same history, and I don’t think it would be the same experience.

My projected path to parting ways with Apple didn’t really take place, since I’m now working at a non-profit dedicated to developing an interactive theorem prover and left Apple without any animosity in either direction.

evaneykelen• 2 years ago

In a previous discussion the name of Gary Davidian is mentioned who also — initialy single-handed — did amazing work on architecture changes at Apple. There’s an interview with him in the Computer History Museum archive.

https://news.ycombinator.com/item?id=28914208

https://youtu.be/MVEKt_H3FsI?si=BbRRV51ql1V6DD4r

markus_zhang13• 2 years ago

From wiki it looks like David's emulator is perhaps uses interpreting as wiki says Eric's uses dynamical recompilation and Connectix' is even faster so maybe more optimization.

I tried to find the source code of any without any success.

lproven3• 2 years ago

All this stuff is or was proprietary, closed-source tech, and what's more, it was tech that gave certain companies strong competitive advantage at particular points in time -- so they had strong incentives to make sure it did not leak.

(I see posters in this thread who do not know what I thought were well-documented parts of the story, so I am trying to spell out the context here.)

Some large reputable companies have histories of stealing other's code, ideas, implementation methods, algorithms etc. and passing them off as their own. IBM, Microsoft, Sun, Apple, Google, Oracle, Digital Research, Lotus -- all were dominant players, all were so accused. Most either backed down, or re-wrote, or re-implemented to avoid being sued.

Microsoft more than almost anyone, and it only thrived because it was able to pay other companies off, or simply wait for them to go broke.

Sometimes, how code works can be deduced simply by studying what it does. I worked out how Rsync worked because someone asked me to explain what it did in detail.

Powerquest's PartitionMagic was amazing, black magic tech when it came out. I didn't review v1 because I did not believe what the packaging said; when I reviewed v2, a reader wrote in accusing my employers of doing an elaborate April Fool's joke and pointed out that my name is an anagram of APRIL VENOM.

(If I ever branch out into fiction, that's my pseudonym.)

Now, the revolutionary functionality of PartitionMagic is just an option in one screen of some installation programs. It's valueless now. Once people saw it working, they could work out how it was done, and then do it, and it ceased to have value.

Very fast emulation is not such a thing. Setting aside sheer Moore's Law/Dennard scaling brute horsepower, efficient emulation during the short window of processor architecture transitions is a massive commercial asset.

Apple has done it 3 times between 4 architectures.

68000 -> PowerPC PowerPC -> x86 x86-64 -> Arm64

Nobody else has ever done so many.

IBM bought Transitive for QuickTransit, but it's not clear how it used it. Its major architecture change was IBM i. Originally OS/400 on AS/400, a derivative of the System 36 minicomputer, it successfully moved this to POWER servers. However, there is a translation layer in the architecture, so it didn't need Transitive for that.

But IBM has bought many radical tech companies and not used the tech. E.g. Rembo, an amazing Linux-based boot-time network-boot fleet deployment tool it never really commercialised.

Microsoft bought Connectix for VirtualPC, kept the disk formats and management UI and threw away everything else, because Intel and AMD bundled the core virtualisation tech.

I know a little of the binary translation tech because the man who wrote it flew across the Altantic for me to interview him.

All thrown away, but today, it's valueless anyway.

At the time, though, very valuable.

ein0p• 2 years ago

Apple just seems to be bleeding talent left and right. I wonder what's going on over there to cause people to leave when the job market is as uncertain as it is right now.

raverbashing• 2 years ago

Citation needed?

I mean, there will always be long tenured people leaving, even without offers on the table

Some jobs get old eventually

blitzar• 2 years ago

The 20th million doesn't hit as hard as the 19th and when you make 2x your salary on the dividends on your stock you start to wonder why not just do something more interesting.

tchbnl• 2 years ago

Sometimes people just want to work on cool stuff and have the luxury of being able to do that. Rosetta 2 is shipped and done.

turnsout• 2 years ago

You could have posted this in 1985 and been right. Talented people have options.

danielktdoranie• 2 years ago

I am pretty sure “lean” is that codeine cough syrup rappers drink

dilsmatchanov• 2 years ago

https://youtu.be/4Or-5OLCNDA?si=mzd_o0573HPgCVrl&t=51

hinkley2• 2 years ago

The audio on this is about the worst I’ve ever heard on YouTube. I fast forwarded and at least he stops playing that loud music over his quiet voice, but damn.

He gets off topic a lot (bullies, amphetamine salts??) and spends the entire time talking to the commenters not the video recording.

Surely, there’s a better video out there than this.

revskill• 2 years ago

The linkedin back button is weird. Instead of coming back to hn after back button, it goes to its homepage.

Yujf• 2 years ago

Its not weird its just disgusting. The back button should go back

jviotti• 2 years ago

How is the Lean non-profit getting funded to be able to afford such great devs? How does that work in general?

Rosetta 2 creator leaves Apple to work on Lean full-time

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