Jon Gjengset
@jonhoo.eu
Rust live-coder and OSS tinkerer who loves teaching. I try to maintain a high SNR. Wrote Rust for Rustaceans. At Helsing.ai. Formerly AWS. Co-founded ReadySet. @jonhoo elsewhere. he/him/they
Not *too* much actual ANTLR stuff in there unfortunately, but at least I got to shout out your work in a small way :D Issues now filed:
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
February 8, 2026 at 9:57 PM
Not *too* much actual ANTLR stuff in there unfortunately, but at least I got to shout out your work in a small way :D Issues now filed:
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
- github.com/antlr4rust/a...
They _are_ automated, so can't guarantee they're all useful, but from a glance and without knowing the internals of the ANTLR4 Rust code, they _seem_ legitimate.
February 8, 2026 at 9:24 PM
They _are_ automated, so can't guarantee they're all useful, but from a glance and without knowing the internals of the ANTLR4 Rust code, they _seem_ legitimate.
And third, I've had the LLM do some benchmarking of avdl, and it's come up with some hotspots in the ANTLR4 Rust code based on the resulting flamegraphs — would you be interested in its reports, or not so much?
February 8, 2026 at 9:24 PM
And third, I've had the LLM do some benchmarking of avdl, and it's come up with some hotspots in the ANTLR4 Rust code based on the resulting flamegraphs — would you be interested in its reports, or not so much?
@alex.wcgw.dev Hey Alex! First, thanks a lot for taking on ownership of ANTLR4 for Rust! Second, I see you made some improvements to the README over the past couple of days — was that because of my stream by any chance? 😅
February 8, 2026 at 9:24 PM
@alex.wcgw.dev Hey Alex! First, thanks a lot for taking on ownership of ANTLR4 for Rust! Second, I see you made some improvements to the README over the past couple of days — was that because of my stream by any chance? 😅
Recording of our "port avro-tools' Java-based idl-to-json tool to Rust using an LLM" adventure is now on YouTube! We got to an initial working implementation in ~4hrs (though still bugs to iron out in future iterations), which isn't too shabby! Code at github.com/jonhoo/avdl.
youtu.be/vmKvw73V394
youtu.be/vmKvw73V394
impl Rust: Avro IDL tool in Rust via ANTLR
YouTube video by Jon Gjengset
youtu.be
February 6, 2026 at 10:26 PM
Recording of our "port avro-tools' Java-based idl-to-json tool to Rust using an LLM" adventure is now on YouTube! We got to an initial working implementation in ~4hrs (though still bugs to iron out in future iterations), which isn't too shabby! Code at github.com/jonhoo/avdl.
youtu.be/vmKvw73V394
youtu.be/vmKvw73V394
As for the LLM bit — I think this is an ideal powercoding (LLM + code review) use-case since we a) have access to the existing Java code and b) there's an infinite supply of trusted tests (the same IDL passed to the Java tool should produce the same JSON). But let's see how it goes!
February 2, 2026 at 6:57 PM
As for the LLM bit — I think this is an ideal powercoding (LLM + code review) use-case since we a) have access to the existing Java code and b) there's an infinite supply of trusted tests (the same IDL passed to the Java tool should produce the same JSON). But let's see how it goes!
If you don't know Avro, it's Apache's equivalent to Google's Protocol Buffers. See avro.apache.org/docs/1.12.0/....
IDL Language
Introduction This document defines Avro IDL, a higher-level language for authoring Avro schemata. Before reading this document, you should have familiarity with the concepts of schemata and protocols,...
avro.apache.org
February 2, 2026 at 6:57 PM
If you don't know Avro, it's Apache's equivalent to Google's Protocol Buffers. See avro.apache.org/docs/1.12.0/....
Friday 9a UTC (everytimezone.com/s/5903cd46) sounds like a good time for a stream! This time, we'll try to port Avro's IDL-to-JSON tool from Java to Rust (with LLM help), leveraging the fact that their grammar is written using ANTLR to make our job easier. Come join me 🎉
youtube.com/live/NqV_KhD...
youtube.com/live/NqV_KhD...
impl Rust: Avro IDL tool in Rust via ANTLR
YouTube video by Jon Gjengset
youtube.com
February 2, 2026 at 6:57 PM
Friday 9a UTC (everytimezone.com/s/5903cd46) sounds like a good time for a stream! This time, we'll try to port Avro's IDL-to-JSON tool from Java to Rust (with LLM help), leveraging the fact that their grammar is written using ANTLR to make our job easier. Come join me 🎉
youtube.com/live/NqV_KhD...
youtube.com/live/NqV_KhD...
The recording of the new year's Q&A stream is now up, with all the questions annotated for easy skipping! youtu.be/S_zp82fYrGw
January 2026 Q&A
YouTube video by Jon Gjengset
youtu.be
January 2, 2026 at 8:44 AM
The recording of the new year's Q&A stream is now up, with all the questions annotated for easy skipping! youtu.be/S_zp82fYrGw
Quick reminder that this is coming up. Lots of good questions have come in, so please take some time to go in and vote for the ones you care the most about!
We're nearing the new year, so time for another Jan 1st Q&A! Ask questions at wewerewondering.com/event/01KDDA... — none too big or small. I'll get to as many as I can, and upload the recording after the fact. Stream starts 1/1/26 at 2:30p UTC @ youtube.com/live/g1ZgInF.... Hope to see you there ❤️
Q&A
Zero-setup, free tool for running live Q&A sessions, including question submission and voting.
wewerewondering.com
December 30, 2025 at 12:38 PM
Quick reminder that this is coming up. Lots of good questions have come in, so please take some time to go in and vote for the ones you care the most about!
In other timezones: everytimezone.com/s/9a5b6b03
Every Time Zone Converter
Easily find the exact time difference with the visual Time Zone Converter. Find meeting times for your contacts, locations and places around the world. Never warp your brain with time zone math again.
everytimezone.com
December 26, 2025 at 1:00 PM
In other timezones: everytimezone.com/s/9a5b6b03
We're nearing the new year, so time for another Jan 1st Q&A! Ask questions at wewerewondering.com/event/01KDDA... — none too big or small. I'll get to as many as I can, and upload the recording after the fact. Stream starts 1/1/26 at 2:30p UTC @ youtube.com/live/g1ZgInF.... Hope to see you there ❤️
Q&A
Zero-setup, free tool for running live Q&A sessions, including question submission and voting.
wewerewondering.com
December 26, 2025 at 12:58 PM
We're nearing the new year, so time for another Jan 1st Q&A! Ask questions at wewerewondering.com/event/01KDDA... — none too big or small. I'll get to as many as I can, and upload the recording after the fact. Stream starts 1/1/26 at 2:30p UTC @ youtube.com/live/g1ZgInF.... Hope to see you there ❤️
Okay, this is pretty cool.
December 8, 2025 at 11:08 AM
Okay, this is pretty cool.
Video of the One Billion Row Challenge stream is now up at youtu.be/tCY7p6dVAGE! We got down to 1.2s without any external dependencies, and it was a fun journey down lots of performance rabbit holes (only some of which panned out 😅). It is over 10h, but hopefully the chapters in the video help!
November 30, 2025 at 8:36 PM
Video of the One Billion Row Challenge stream is now up at youtu.be/tCY7p6dVAGE! We got down to 1.2s without any external dependencies, and it was a fun journey down lots of performance rabbit holes (only some of which panned out 😅). It is over 10h, but hopefully the chapters in the video help!
Oh, forgot the link to see the time in your timezone. YouTube should show it, but otherwise, you can use everytimezone.com/s/70bf2c9d 🕚 [4/3]
Every Time Zone Converter
Easily find the exact time difference with the visual Time Zone Converter. Find meeting times for your contacts, locations and places around the world. Never warp your brain with time zone math again.
everytimezone.com
November 24, 2025 at 9:16 PM
Oh, forgot the link to see the time in your timezone. YouTube should show it, but otherwise, you can use everytimezone.com/s/70bf2c9d 🕚 [4/3]
There are already several Rust implementations (github.com/gunnarmorlin...), this excellent write-up (curiouscoding.nl/posts/1brc/), and even an existing stream (www.youtube.com/watch?v=Q-0d...), but I'm hoping that walking through the process live will still be a good teaching exercise. [3/3]
One Billion Row Challenge
Table of Contents External links The problem Initial solution: 105s First flamegraph Bytes instead of strings: 72s Manual parsing: 61s Inline hash keys: 50s Faster hash function: 41s A new flame graph...
curiouscoding.nl
November 24, 2025 at 9:14 PM
There are already several Rust implementations (github.com/gunnarmorlin...), this excellent write-up (curiouscoding.nl/posts/1brc/), and even an existing stream (www.youtube.com/watch?v=Q-0d...), but I'm hoping that walking through the process live will still be a good teaching exercise. [3/3]
Come join me on Saturday at 11am UTC over on youtube.com/live/g2EKNXK..., and we'll see what we can squeeze out of it 🏎️ [2/3]
One Billion Row Challenge in Rust
YouTube video by Jon Gjengset
youtube.com
November 24, 2025 at 9:14 PM
Come join me on Saturday at 11am UTC over on youtube.com/live/g2EKNXK..., and we'll see what we can squeeze out of it 🏎️ [2/3]
I'm late to the party, but the One Billion Row Challenge (github.com/gunnarmorlin...) feels like an excellent way to dig into optimizing Rust code and learning somethings about assembly, SIMD, performance profiling, and just CPUs in general in the process, so let's take it on live! [1/3]
GitHub - gunnarmorling/1brc: 1️⃣🐝🏎️ The One Billion Row Challenge -- A fun exploration of how quickly 1B rows from a text file can be aggregated with Java
1️⃣🐝🏎️ The One Billion Row Challenge -- A fun exploration of how quickly 1B rows from a text file can be aggregated with Java - gunnarmorling/1brc
github.com
November 24, 2025 at 9:14 PM
I'm late to the party, but the One Billion Row Challenge (github.com/gunnarmorlin...) feels like an excellent way to dig into optimizing Rust code and learning somethings about assembly, SIMD, performance profiling, and just CPUs in general in the process, so let's take it on live! [1/3]
@adamconover.net is here though, and also worth checking out — not as focused on tech and policy, more on fact-finding journalism on everyday topics with a humouristic bent (e.g., "Adam ruins everything").
November 9, 2025 at 8:01 PM
@adamconover.net is here though, and also worth checking out — not as focused on tech and policy, more on fact-finding journalism on everyday topics with a humouristic bent (e.g., "Adam ruins everything").
I don't think Cory is on Bluesky, but his website is pluralistic.net. Highly recommend giving his writings a read (though be warned — he writes a *lot*).
Pluralistic: Daily links from Cory Doctorow – No trackers, no ads. Black type, white background. Privacy policy: we don't collect or retain any data at all ever period.
pluralistic.net
November 9, 2025 at 4:42 PM
I don't think Cory is on Bluesky, but his website is pluralistic.net. Highly recommend giving his writings a read (though be warned — he writes a *lot*).
I've been a fan of Cory Doctorow for ages, and this episode of Adam Conover's podcast is a great synthesis of his observations on the tech industry across the board, both what's broken and how we fix it. And a slew of other great insights. Highly recommended listen!
headgum.com/factually-wi...
headgum.com/factually-wi...
Factually! with Adam Conover - The Ensh*ttification of Everything with Cory Doctorow
The internet is getting shittier. Hell, the whole world is getting shittier. The thing is, it’s no accident—it’s by design. The tech giants who run the internet have figured out how to make bank off o...
headgum.com
November 9, 2025 at 4:40 PM
I've been a fan of Cory Doctorow for ages, and this episode of Adam Conover's podcast is a great synthesis of his observations on the tech industry across the board, both what's broken and how we fix it. And a slew of other great insights. Highly recommended listen!
headgum.com/factually-wi...
headgum.com/factually-wi...
On Sunday at 2pm UTC (everytimezone.com?t=68fd6480,348), Ben and I are doing another "What's New in Rust" marathon stream for Rustacean Station! I'm guessing ~5h for part 1 😅 It'll be over at youtube.com/live/6mwVWmK.... Come join us 📺🎉
What's New in Rust 1.81-1.?? Rustacean Station marathon
YouTube video by Jon Gjengset
youtube.com
October 20, 2025 at 7:56 PM
On Sunday at 2pm UTC (everytimezone.com?t=68fd6480,348), Ben and I are doing another "What's New in Rust" marathon stream for Rustacean Station! I'm guessing ~5h for part 1 😅 It'll be over at youtube.com/live/6mwVWmK.... Come join us 📺🎉
In August, I was interviewed by JetBrains about programming and Rust, ranging from the borrow checker, to agentic coding, to hiring. And it's now on YouTube! It's also general enough that it should be interesting even to those not already knee deep in Rust 😅
www.youtube.com/watch?v=nOSx...
www.youtube.com/watch?v=nOSx...
October 9, 2025 at 2:09 PM
In August, I was interviewed by JetBrains about programming and Rust, ranging from the borrow checker, to agentic coding, to hiring. And it's now on YouTube! It's also general enough that it should be interesting even to those not already knee deep in Rust 😅
www.youtube.com/watch?v=nOSx...
www.youtube.com/watch?v=nOSx...
About a month ago, I gave a talk at the Rust Amsterdam meetup about Sguaba (the type-safe spatial math Rust crate), and the recording of that is now online for anyone who wants their head to hurt with frames of reference and coordinate transforms 😅
youtu.be/kESBAiTYMoQ
youtu.be/kESBAiTYMoQ
Sguaba: Type-safe spatial math in Rust
YouTube video by Jon Gjengset
youtu.be
September 29, 2025 at 2:26 PM
About a month ago, I gave a talk at the Rust Amsterdam meetup about Sguaba (the type-safe spatial math Rust crate), and the recording of that is now online for anyone who wants their head to hurt with frames of reference and coordinate transforms 😅
youtu.be/kESBAiTYMoQ
youtu.be/kESBAiTYMoQ
For those who missed the stream, you can find my chat with Maya about Rust, concurrency, left-right, Noria, career development, AI, and a whole host of other random nerdy things on YouTube now!
www.youtube.com/live/kJnrbbt...
www.youtube.com/live/kJnrbbt...
two nerds one stream w/ @jonhoo! 💜 chatting about rust/concurrency/anything you ask about!
YouTube video by Maya
www.youtube.com
September 23, 2025 at 8:42 AM
For those who missed the stream, you can find my chat with Maya about Rust, concurrency, left-right, Noria, career development, AI, and a whole host of other random nerdy things on YouTube now!
www.youtube.com/live/kJnrbbt...
www.youtube.com/live/kJnrbbt...