5 ms·

Many repeat the point of “$165k is cheaper than team of multiple engineers working on the rewrite for a year”, which I think is flawed — the team of engineers w

Many repeat the point of “$165k is cheaper than team of multiple engineers working on the rewrite for a year”, which I think is flawed — the team of engineers would have produced idiomatic rust, and it would take probably 100k+ of tokens more to make the bun in rust idiomatic rust.

Tinkeringz 2mo ago
I feel your estimate of tokens is a few orders of magnitude off, it’s on the low side. I use more (albeit cached) when centering a div.
- Hasnep 2mo ago
  I think they missed a $ sign, i.e. they meant $100k of tokens
- reactordev 2mo ago
  100k tokens is your pre-prompt and your CLAUDE.md as well as a few files from your root.
- rezonant 2mo ago
  This is where we've come to where people proudly proclaim using an AI to do what is a single line of CSS.
  - d0mine 2mo ago
    "centering div" is a classic problem (/trauma/meme) that sounds trivial but had no universal solution (until 2017?).
    - rezonant 2mo ago
      And has a dead simple one today. Also worth noting simple horizontal centering of divs was never a problem, margin: auto was defined in CSS Level 1 in 1996 [1]. It was vertical centering that took a very long time to crack, which really became trivial with Flexbox which was first drafted in 2009[2] but became available unprefixed in browsers between 2012 and 2014 [3] about 13 years ago. [1] https://www.w3.org/TR/REC-CSS1-961217 https://www.w3.org/TR/REC-CSS1-961217 [2] https://www.w3.org/TR/2009/WD-css3-flexbox-20090723/ https://www.w3.org/TR/2009/WD-css3-flexbox-20090723/ [3] https://caniuse.com/flexbox https://caniuse.com/flexbox Subnote: I'm not counting the display: table hacks.
- moralestapia 2mo ago
  What a great joke. I will have to steal it for an upcoming AI tools meeting I have at work. Also, pretty clever as centering a div w/ CSS has been notoriously difficult to achieve.
irishcoffee 2mo ago
> produced idiomatic rust I keep seeing this. What is "un-idiomatic" rust?
- vessenes 2mo ago
  Presumably lots of stuff wrapped in 'unsafe'. I'm not a rust guy or a rust fan, and the last time I wrote something with Rust was like 7 years ago, but to my memory, because of how Rust manages mutability there are many access patterns that are Rust-specific; idiomatic Rust is going to use this patterns but they would be unlikely to show up in a language with a different type system / borrow checker / etc. etc.
  - irishcoffee 2mo ago
    So "unidiomatic" rust means, 'don't use these parts of the language even though they're first-class citizens?' How odd. Lot of mental gymnastics going on there.
    - tribaal 2mo ago
      It's mostly the same in any general purpose programming language though, parts of the language features are meant (or became seens as) tools to be used in very narrow cases, which people less familiar with the language tend to "overuse". Eg. goto/jump, bare "except" statements in python, etc... In Rust, unsafe has its uses and is a first class language feature, but it certainly isn't idiomatic to use it to mimic access patterns from other languages (unless absolutely necessary).
    - flohofwoe 2mo ago
      The Bun author himself writes that the port is not idiomatic Rust: Do the rewrite that looks like we transpiled our Zig code to Rust. We can gradually refactor it to reduce unsafe usage and look more like idiomatic Rust after Bun v1.4 ships. (from: https://bun.com/blog/bun-in-rust https://bun.com/blog/bun-in-rust) The original version of Bun was already a line-by-line (manual) port of esbuild from Go to Zig (also mentioned in this post), so the Zig code already wasn't "Zig-idiomatic" and apparently riddled with problems. That doesn't inspire much confidence in the LLM-translated Rust version tbh.
furyofantares 2mo ago
They also would have produced a team of engineers that knows the Rust codebase.
- busterarm 2mo ago
  This is assuming your engineers don't leave for higher-paying roles elsewhere. The market might be cold generally but for engineers working at these frontier AI companies it's red-hot. And most executives are figuring this into their calculus right now because they were burned badly during COVID. Meta, Google, etc were loose with hiring and engineers flocked from their lower-paying companies in droves. The brain drain was real. One public company I was at lost nearly 2/3rds of their engineers and mostly to Meta (granted, they had other problems but it was mostly about money -- the offers were excessive). Then market conditions forced them to freeze hiring and they've had a slow exodus of senior talent since as the firefighting has become constant. AI adoption has only accelerated problems for them. We've taken this "only two years and then leave" philosophy to an extreme and now companies are totally justified in not investing in their engineers anymore.
  - ambicapter 2mo ago
    The job-hopping followed from companies not investing in their engineers, not the other way around. It was billed as the only way to get a promotion (which usually would come every 1-2 years).
    - busterarm 2mo ago
      I've been in this industry for a few decades at this point and I was around when this meme was started. It was purely about maxing your compensation because changing jobs nets you more than promotions & raises. I've never met an engineer in my life who truly earned a promotion every year and very few every two. Very few companies have org charts that even support that or have that many levels. This logic/advice only really applies at a few companies and people have adopted it no matter where they work. There's not enough growth/hiring at 95% of companies to even come close. The Peter Principle is also a real thing. Everyone's competence has a ceiling. There's even an implicit understanding of this that people at smaller companies have inflated titles and you typically rank them down 1-2 levels when hiring/acquiring at larger companies. Now I do agree that companies haven't been investing in their engineers, but that doesn't also mean this isn't a vicious cycle. Employers and employees are in a mexican standoff and things are only going to get worse until one side comes to its senses. Employers have all the leverage for it to not be them. For the vast majority of companies the average tenure of an engineer sits between 18 and 30 months. They're also mostly hiring young engineers in their 20s. As an employer what is your upside to making such investments before they're at least mid-career? A lot of people seem to want the world and offer nothing in return for it.
tcfhgj 2mo ago
I doubt file by file rewriting takes as much work as rewriting and refactoring the code - especially at this scale.
rcxdude 2mo ago
Would they have, in a year? The general plan of attack would likely still be the same: rewrite it in rust while keeping the structure as similar as possible, no matter how unidiomatic, then adjusting the design to make it more idiomatic to rust. Doing both at once is much harder.
- reliabilityguy 2mo ago
  > Doing both at once is much harder. I think with sequential approach (translate -> make idiomatic) it is easier. However, I am not sure that monetary difference is going to be as stark as $165k vs 3 engineers/year. Especially, if you consider that no one knows that is what in the code at the end. Sure, you can argue that now it doesn’t matter — agents and all that, but I am not so sure.
witx 2mo ago
Yes this is a typical case of showing results fast. I wonder what the cost for the remaining 10℅ of debugging and fixing all the bloat will be. Not so cheap I am guessing
nozzlegear 2mo ago
IMO a team of engineers (presuming this is pre-AI) would have improved the existing Zig codebase, rather than spent time and money on a Rust port in the first place. In fact, I still think most teams of engineers would choose to improve what they have even now, circa AI.
tomjakubowski 2mo ago
Yes, and curiously many of the tellings of this story don't account for the costs of the human software engineers (Jarred and the other bun team members) who guided all of this work.
asp_hornet 2mo ago
> the team of engineers would have produced idiomatic rust Not necessarily. Didn’t Microsoft port the TS compiler to Go and they did it by translating the TS? It wasn’t idiomatic Go.

Tinkeringz 2mo ago

I feel your estimate of tokens is a few orders of magnitude off, it’s on the low side. I use more (albeit cached) when centering a div.

Hasnep 2mo ago
I think they missed a $ sign, i.e. they meant $100k of tokens
reactordev 2mo ago
100k tokens is your pre-prompt and your CLAUDE.md as well as a few files from your root.
rezonant 2mo ago
This is where we've come to where people proudly proclaim using an AI to do what is a single line of CSS.
- d0mine 2mo ago
  "centering div" is a classic problem (/trauma/meme) that sounds trivial but had no universal solution (until 2017?).
  - rezonant 2mo ago
    And has a dead simple one today. Also worth noting simple horizontal centering of divs was never a problem, margin: auto was defined in CSS Level 1 in 1996 [1]. It was vertical centering that took a very long time to crack, which really became trivial with Flexbox which was first drafted in 2009[2] but became available unprefixed in browsers between 2012 and 2014 [3] about 13 years ago. [1] https://www.w3.org/TR/REC-CSS1-961217 https://www.w3.org/TR/REC-CSS1-961217 [2] https://www.w3.org/TR/2009/WD-css3-flexbox-20090723/ https://www.w3.org/TR/2009/WD-css3-flexbox-20090723/ [3] https://caniuse.com/flexbox https://caniuse.com/flexbox Subnote: I'm not counting the display: table hacks.
moralestapia 2mo ago
What a great joke. I will have to steal it for an upcoming AI tools meeting I have at work. Also, pretty clever as centering a div w/ CSS has been notoriously difficult to achieve.

irishcoffee 2mo ago

> produced idiomatic rust I keep seeing this. What is "un-idiomatic" rust?

vessenes 2mo ago
Presumably lots of stuff wrapped in 'unsafe'. I'm not a rust guy or a rust fan, and the last time I wrote something with Rust was like 7 years ago, but to my memory, because of how Rust manages mutability there are many access patterns that are Rust-specific; idiomatic Rust is going to use this patterns but they would be unlikely to show up in a language with a different type system / borrow checker / etc. etc.
- irishcoffee 2mo ago
  So "unidiomatic" rust means, 'don't use these parts of the language even though they're first-class citizens?' How odd. Lot of mental gymnastics going on there.
  - tribaal 2mo ago
    It's mostly the same in any general purpose programming language though, parts of the language features are meant (or became seens as) tools to be used in very narrow cases, which people less familiar with the language tend to "overuse". Eg. goto/jump, bare "except" statements in python, etc... In Rust, unsafe has its uses and is a first class language feature, but it certainly isn't idiomatic to use it to mimic access patterns from other languages (unless absolutely necessary).
  - flohofwoe 2mo ago
    The Bun author himself writes that the port is not idiomatic Rust: Do the rewrite that looks like we transpiled our Zig code to Rust. We can gradually refactor it to reduce unsafe usage and look more like idiomatic Rust after Bun v1.4 ships. (from: https://bun.com/blog/bun-in-rust https://bun.com/blog/bun-in-rust) The original version of Bun was already a line-by-line (manual) port of esbuild from Go to Zig (also mentioned in this post), so the Zig code already wasn't "Zig-idiomatic" and apparently riddled with problems. That doesn't inspire much confidence in the LLM-translated Rust version tbh.

furyofantares 2mo ago

They also would have produced a team of engineers that knows the Rust codebase.

busterarm 2mo ago
This is assuming your engineers don't leave for higher-paying roles elsewhere. The market might be cold generally but for engineers working at these frontier AI companies it's red-hot. And most executives are figuring this into their calculus right now because they were burned badly during COVID. Meta, Google, etc were loose with hiring and engineers flocked from their lower-paying companies in droves. The brain drain was real. One public company I was at lost nearly 2/3rds of their engineers and mostly to Meta (granted, they had other problems but it was mostly about money -- the offers were excessive). Then market conditions forced them to freeze hiring and they've had a slow exodus of senior talent since as the firefighting has become constant. AI adoption has only accelerated problems for them. We've taken this "only two years and then leave" philosophy to an extreme and now companies are totally justified in not investing in their engineers anymore.
- ambicapter 2mo ago
  The job-hopping followed from companies not investing in their engineers, not the other way around. It was billed as the only way to get a promotion (which usually would come every 1-2 years).
  - busterarm 2mo ago
    I've been in this industry for a few decades at this point and I was around when this meme was started. It was purely about maxing your compensation because changing jobs nets you more than promotions & raises. I've never met an engineer in my life who truly earned a promotion every year and very few every two. Very few companies have org charts that even support that or have that many levels. This logic/advice only really applies at a few companies and people have adopted it no matter where they work. There's not enough growth/hiring at 95% of companies to even come close. The Peter Principle is also a real thing. Everyone's competence has a ceiling. There's even an implicit understanding of this that people at smaller companies have inflated titles and you typically rank them down 1-2 levels when hiring/acquiring at larger companies. Now I do agree that companies haven't been investing in their engineers, but that doesn't also mean this isn't a vicious cycle. Employers and employees are in a mexican standoff and things are only going to get worse until one side comes to its senses. Employers have all the leverage for it to not be them. For the vast majority of companies the average tenure of an engineer sits between 18 and 30 months. They're also mostly hiring young engineers in their 20s. As an employer what is your upside to making such investments before they're at least mid-career? A lot of people seem to want the world and offer nothing in return for it.

tcfhgj 2mo ago

I doubt file by file rewriting takes as much work as rewriting and refactoring the code - especially at this scale.

rcxdude 2mo ago

Would they have, in a year? The general plan of attack would likely still be the same: rewrite it in rust while keeping the structure as similar as possible, no matter how unidiomatic, then adjusting the design to make it more idiomatic to rust. Doing both at once is much harder.

reliabilityguy 2mo ago
> Doing both at once is much harder. I think with sequential approach (translate -> make idiomatic) it is easier. However, I am not sure that monetary difference is going to be as stark as $165k vs 3 engineers/year. Especially, if you consider that no one knows that is what in the code at the end. Sure, you can argue that now it doesn’t matter — agents and all that, but I am not so sure.

witx 2mo ago

Yes this is a typical case of showing results fast. I wonder what the cost for the remaining 10℅ of debugging and fixing all the bloat will be. Not so cheap I am guessing

nozzlegear 2mo ago

IMO a team of engineers (presuming this is pre-AI) would have improved the existing Zig codebase, rather than spent time and money on a Rust port in the first place. In fact, I still think most teams of engineers would choose to improve what they have even now, circa AI.

tomjakubowski 2mo ago

Yes, and curiously many of the tellings of this story don't account for the costs of the human software engineers (Jarred and the other bun team members) who guided all of this work.

asp_hornet 2mo ago

> the team of engineers would have produced idiomatic rust Not necessarily. Didn’t Microsoft port the TS compiler to Go and they did it by translating the TS? It wasn’t idiomatic Go.