iiinova — where your digital self keeps evolving

Jon Gjengset @jonhoo.eu · 29/08/2026

I got a 2-meow server rack. Highly recommend.

Two cats exploring the inside of a 12U server rack.

Jon Gjengset @jonhoo.eu · 19/07/2026

Recording of yesterday's open source maintenance stream is now up! We got through left-right (a concurrency primitive), HdrHistogram (a fun data structure), rust-imap (you guessed it), and inferno (the Rust port of flamegraph) in about 5 hours — OSS is no joke 😅 youtu.be/bAINppA0BSU

youtu.be

Open Source Maintenance, 2026-07-18

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 14/07/2026

Haven't done an open source maintenance stream in a while, and by now I have a few open open-source issues and pull requests I'm behind on, so let's rectify that! Stream will be this Saturday at 1pm UTC on youtube.com/live/7h7ciBk... — see you there!

youtube.com

Open source maintenance

YouTube video by Jon Gjengset

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Reposted by Jon Gjengset

Armin Ronacher @mitsuhiko.at · 11/04/2026

After the AI Engineer conference, which was full of useful criticism, I remembered that the most confident takes on AI often came from the least exposure. Rejection is easy, trial and error is expensive. I wrote about it. lucumr.pocoo.org/2026/4/11/th...

lucumr.pocoo.org

The Center Has a Bias

Why a measured position on AI tends to lean towards actually trying it.

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Jon Gjengset @jonhoo.eu · 04/04/2026

Recording of yesterday's stream implementing a WAV noise file generator in #rust is now up on YouTube! We managed to get white, pink, brownian, blue, violet, and grey (psychoacoustic!) noise all implemented, so I'll count that as a success 🔊 youtu.be/zOTE4BN59u4

youtu.be

impl Rust: WAV noise generator

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 01/04/2026

A few weeks ago I was interviewed by Daniel from Rock the JVM, a channel (unsurprisingly) for folks in the JVM ecosystem. It was fun to chat about Rust with someone "from the outside", and if you want to hear it, it's now up on his YouTube channel! youtu.be/Cg8gASzqqOs?...

youtu.be

Jon Gjengset on Rust Internals, Vibe Coding, and Teaching by Streaming

YouTube video by Rock the JVM

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Jon Gjengset @jonhoo.eu · 31/03/2026

The past few streams have been pretty high level, but not this time! Friday at 4p UTC (everytimezone.com?t=69cf0300,3c0), we're going back down to "what bits go where". We'll try to write an audio generator that produces WAV files with white/pink/brown noise by hand 🔊 youtube.com/live/BKHE7st...

youtube.com

impl Rust: WAV noise generator

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 26/03/2026

Back in January I gave a talk at Jane Street titled "Are Mutexes Slow?" (I gave a lightning version of it at @rustikon.dev last week!). And it's now up on YouTube if you're interested in wonky details about CPU cache coherence and the cost of coordination! www.youtube.com/watch?v=tND-...

youtube.com

The Cost of Concurrency Coordination with Jon Gjengset

YouTube video by Jane Street

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Jon Gjengset @jonhoo.eu · 05/03/2026

Sadly I can't make it to the inaugural TokioConf (Portland, Apr 20-22), but I do have a 15% off code I've been told to hand out to people excited to go! So, if you've been on the fence, ping me and I'll see what I can do! More on the conf & who it's for (most people!) here: tokio.rs/blog/2026-03...

tokio.rs

TokioConf Update: What to Expect | Tokio - An asynchronous Rust runtime

Tokio is a runtime for writing reliable asynchronous applications with Rust. It provides async I/O, networking, scheduling, timers, and more.

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Jon Gjengset @jonhoo.eu · 19/02/2026

In January, @anishathalye.bsky.social, @josejg.bsky.social, and I returned to @csail.mit.edu to teach Missing Semester, a class on topics we miss from most CS programs—tools and techniques that everyone should know, like Bash, Git, CI, and AI tools. Today, we’re releasing the course for free online!

The Missing Semester of your CS education [MIT IAP 2026] - https://missing.csail.mit.edu

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Jon Gjengset @jonhoo.eu · 08/02/2026

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...

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Jon Gjengset @jonhoo.eu · 08/02/2026

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.

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Jon Gjengset @jonhoo.eu · 08/02/2026

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?

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Jon Gjengset @jonhoo.eu · 08/02/2026

@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? 😅

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Jon Gjengset @jonhoo.eu · 06/02/2026

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

impl Rust: Avro IDL tool in Rust via ANTLR

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 02/02/2026

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!

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Jon Gjengset @jonhoo.eu · 02/02/2026

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

impl Rust: Avro IDL tool in Rust via ANTLR

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 02/01/2026

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

youtu.be

January 2026 Q&A

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 30/12/2025

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!

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Jon Gjengset @jonhoo.eu · 26/12/2025

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 ❤️

wewerewondering.com

Q&A

Zero-setup, free tool for running live Q&A sessions, including question submission and voting.

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Jon Gjengset @jonhoo.eu · 08/12/2025

Okay, this is pretty cool.

YouTube silver creator award presented to Jon Gjengset for passing 100,000 subscribers. J and Ferris plushies in the background.

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Jon Gjengset @jonhoo.eu · 30/11/2025

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!

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Jon Gjengset @jonhoo.eu · 24/11/2025

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]

curiouscoding.nl

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...

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Jon Gjengset @jonhoo.eu · 24/11/2025

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]

youtube.com

One Billion Row Challenge in Rust

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 24/11/2025

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.com

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

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Jon Gjengset @jonhoo.eu · 09/11/2025

@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").

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Jon Gjengset @jonhoo.eu · 09/11/2025

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.net

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.

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Jon Gjengset @jonhoo.eu · 09/11/2025

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! 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...

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Jon Gjengset @jonhoo.eu · 20/10/2025

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 📺🎉

youtube.com

What's New in Rust 1.81-1.?? Rustacean Station marathon

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 09/10/2025

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...

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Jon Gjengset @jonhoo.eu · 29/09/2025

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

Sguaba: Type-safe spatial math in Rust

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 23/09/2025

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...

youtube.com

two nerds one stream w/ @jonhoo! 💜 chatting about rust/concurrency/anything you ask about!

YouTube video by Maya

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Jon Gjengset @jonhoo.eu · 17/09/2025

Sunday at 6pm UTC (everytimezone.com/s/4a616697), I'll be on Maya Rainer's stream to talk about concurrency and the left-right crate. We'll take a bunch of questions from chat, so bring your burning `Send + Sync` questions :D Stream will be over at www.twitch.tv/mayarainer/s... — see you there!

twitch.tv

mayarainer Schedule - Twitch

Check out mayarainer stream schedule, and set reminders so you don’t miss out!

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Jon Gjengset @jonhoo.eu · 05/08/2025

For those curious about the third proposed Sguaba feature, I ended up writing it myself and having Claude suggest tests. Worked quite well! Given the nuances in designing this mechanism, I suspect it would have struggled quite a lot with implementing it from scratch 😅 github.com/helsing-ai/s...

github.com

feat: make Vector generic over unit by jonhoo · Pull Request #31 · helsing-ai/sguaba

This adds support for velocity and acceleration vectors alongside the original length vectors, enabling users to store vectors that hold velocity or acceleration without losing that semantic inform...

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Reposted by Jon Gjengset

anishathalye.bsky.social @anishathalye.bsky.social · 05/08/2025

Missing Semester has grown past 100K subscribers on YouTube. Appreciate all the engagement and support! We plan to teach another iteration of the course in January 2026, revising the curriculum and covering new topics like AI IDEs and vibe coding.

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Jon Gjengset @jonhoo.eu · 01/08/2025

Today's "vibe-code non-trivial changes to a Rust crate" stream is up! Got to 2/4 changes and then ran out of tokens on the Claude Pro plan 😅 Still TBD if my Luddite skepticism is apt, but it was fun, interesting, and did shed light on the ups and downs of agentic Rust coding! youtu.be/EL7Au1tzNxE

youtu.be

Vibe coding complex changes in Rust

YouTube video by Jon Gjengset

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Jon Gjengset @jonhoo.eu · 24/07/2025

Change of plans — due to the ongoing heatwave in Oslo, and Norway's general lack of A/C, my office is regularly reaching 32°C/90°F these days. This breaks my brain, and also my camera, so I'm going to move this stream to the same time next week! See you then 👋

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Jon Gjengset @jonhoo.eu · 19/07/2025

My sense from talking to a few folks is that Claude Code is currently the leader of the pack, so was planning to start there

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Jon Gjengset @jonhoo.eu · 18/07/2025

This will be my first foray into agentic AI-based coding, so you'll get my unfiltered first-and-second impressions 😅 And the opportunity to point out how wrong I've been all along if it turns out to be a humbling experience 👀 Ultimately, I'm aiming for a reality-check for my skepticism!

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Jon Gjengset @jonhoo.eu · 18/07/2025

Those who have followed me for a while may already know that I'm a bit of an ML Luddite. Well, it's time to challenge that. Next Friday at 17:30 UTC, I'll be attempting to vibe code complex changes to the Rust crate Sguaba (github.com/helsing-ai/s...) — come laugh at me! youtube.com/live/3NGXL_8...

youtube.com

Vibe coding complex changes in Rust

Those who have followed me for a while may already know that I'm a bit of an ML Luddite — it's not that I'm opposed to the use of ML-based tools, but rather that I haven't personally found much use fo...

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Jon Gjengset @jonhoo.eu · 26/06/2025

Excellent! Now we just need the same for rustc lints 👀

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Jon Gjengset @jonhoo.eu · 25/06/2025

That helps, for sure. But still requires that a) they all come with automated fixes, b) those fixes are generally correct, and c) teams prioritize reviewing those. It's also generally inefficient to be forced to review reactively, than decide when to bulk-address.

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Jon Gjengset @jonhoo.eu · 25/06/2025

Oh, for individual projects this isn't *that* bad. The issue arises when you have this across all of a company's projects. They all have other things to prioritize, and end up simply running with older Rust versions instead. Which is then a security risk. And then their dependencies fall behind...

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Jon Gjengset @jonhoo.eu · 25/06/2025

Challenge with this is that it means I'm blocked from upgrading my Rust version until I've addressed the lints. Which also may mean I'm blocked from updating dependencies that make use of newer Rust. The current system soft-forces that the Rust upgrade and lint fixes must happen jointly and first

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Jon Gjengset @jonhoo.eu · 25/06/2025

I want this so badly. I remember having a chat with Niko and Felix about it ages ago, and I think their main concern was that it'll end up being approximate at best (e.g., if the semantics of a liny changes). But I think that'd still be a huge net positive.

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Jon Gjengset @jonhoo.eu · 24/06/2025

The other day I was interviewed about Helsing, working in defense, and what it's like specifically to work at Helsing. We ended up covering quite a lot of questions I commonly get (and that I know people have but don't ask), so if you're curious about any aspect of it, give it a read!

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Jon Gjengset @jonhoo.eu · 22/06/2025

Or is that need perhaps sufficiently covered by ChatGPT and friends?

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