Moritz Hamann

Moritz Hamann

@moritzhamann.com

Engineering Manager at Bloomberg LP. Opinions are my own. Mastodon: @MoritzHamann@mastodon.social https://moritzhamann.com

203 followers86 following218 posts

Moritz Hamann reposted

Shriram Krishnamurthi
@shriram.bsky.social

We should maximize the amount of proof we can get out of AI while the money cannon is on. It's like early days of Uber, except the benefits are 100x more tangible. A fully-verified hw+sw stack? That's like gold everyone can share w/out having to divide. Generational opportunity.

Moritz Hamann
@moritzhamann.com

trying out firefox again. Apple's password manager does not work out of the box, the AI integration doesn't have any interesting integration, but at least the tab syncing works better than in safari.

Moritz Hamann
@moritzhamann.com

re AI: Just be bold. Either fully integrate it with tools for current page state, debugging tools, automation or just make it a full extension. This half baked version feels very risk adverse in either direction and is ultimately the worst of both worlds ...

Moritz Hamann
@moritzhamann.com

Me: maybe I should finally learn plain old C. What could be a good project? maybe a postscript interpreter? Downloading the spec: 912 pages ... maybe not

Moritz Hamann
@moritzhamann.com

Ok note to my future self: Looks like embedding google fonts via <link> will only serve a trimmed down version of the font that has most of the box drawing glyphs missing. Downloading and serving it from the backend fixes it ...

Moritz Hamann
@moritzhamann.com

got an iPhone for the first time. Current progress: WhatsApp unable to move chat history in 2026 (WeChat had 0 problems). Only option: "Move to iOS" Android app. Except this app only works when the iPhone is still in factory reset mode (obviously don't tell you that before hand)

Moritz Hamann
@moritzhamann.com

Getting a bit into Rust again and have to say that ChatGPT is great to figure out all the little syntax variations that can be useful from time to time, e.g. `match` vs `if let` vs `let ... else`

Moritz Hamann reposted

Rob Palmer
@robpalmer.bsky.social

ECMAScript EXTRA-SPECIAL excitement 😉 🚨🚨🚨 IT'S ABOUT TIME! 🚨🚨🚨 Congrats to @ptomato.name on advancing Temporal to Stage 4 at @tc39.es today 🎉 Temporal is the replacement for the JavaScript Date API 👍

Jason Williams@jason-williams.co.uk

Temporal is now Stage 4 at TC39 🎂🎂🎂 Thanks to all the other champions of JavaScript's new date-time API. It has been a wild ride over many years! I wrote a blog post explaining how we got here 📜 bloomberg.github.io/js-blog/post...

Moritz Hamann
@moritzhamann.com

I do like the tooling, the backwards compatibility and ecosystem of go, but some of those decisions in the stdlib are really ... interesting. `http.handle("/", handler)` will match every single ULR, `http.handle("/{$}", handler)` only "/"...

Moritz Hamann reposted

Anil Madhavapeddy
@avsm.amok.recoil.org.ap.brid.gy

OxCaml isn't just useful due to its language extensions; it's making us think through how to engineer OCaml code to be lower allocation by default even before switching. See Mark's progress on an MP3 decoder to speed it up 10x https://www.tunbury.org/2026/02/11/ocaml-mp3/

tunbury.orgOptimizing an MP3 Codec with OCaml/OxCamlAfter reading Anil’s post about his zero-allocation HTTP parser httpz, I decided to apply some OxCaml optimisation techniques to my pure OCaml MP3 encoder/decoder. The OCaml-based MP3 encoder/decoder has been the most ambitious project I’ve tried in Opus 4.5. It was a struggle to get it over the line, and I even needed to read large chunks of the ISO standard and get to grips with some of the maths and help the AI troubleshoot. # Profiling an OCaml MP3 Decoder with Landmarks Before dividing into OxCaml, I wanted to get a feel for the current performance and also to make obvious non-OxCaml performance improvements; otherwise, I would be comparing an optimised OxCaml version with an underperforming OCaml version. It was 40 times slower than `ffmpeg`: 29.5 seconds to decode a 3-minute file versus 0.74 seconds. I used the landmarks profiling library to identify and fix the bottlenecks, bringing decode time down to 3.5 seconds (a 8x speedup). ## Setting Up Landmarks Landmarks is an OCaml profiling library that instruments functions and reports cycle counts. It was easy to add to the project (*) with a simple edit of the `dune` file: (libraries ... landmarks) (preprocess (pps landmarks-ppx --auto)) The `--auto` flag automatically instruments every top-level function — no manual annotation needed. Running the decoder with `OCAML_LANDMARKS=on` prints a call tree with cycle counts and percentages. > (*) It needed OCaml 5.3.0 for `landmarks-ppx` compatibility; it wouldn’t install on OCaml 5.4.0 due to a ppxlib version constraint. ## Issues 78% of the time was spent in the Huffman decoding, specifically `decode_pair`. The implementation read one bit at a time, then scanned the table for a matching Huffman code. I initially tried a Hashtbl, which was much better than the scan before deciding to use array lookup instead. The bitstream operations still accounted for much of the time, but these could be optimised with appropriate `Bytes.get_...` calls, as the most frequent path is reading 32 bits in big endian layout. The profile now showed `find_sfb_long` consuming 3.4 billion cycles inside requantization. This function does a linear search through scalefactor band boundaries for every one of the 576 frequency lines, every granule, every frame. Switching to precomputed 576-entry arrays mapping each frequency line directly to its scalefactor band index. There were some additional tweaks, such as adding more precomputed lookup tables stored in `floatarray`, using `[@inline]` and `unsafe_get`, `land` instead of `mod`. After this, no single function dominated the profile, and I could move on to OxCaml. # OxCaml OxCaml has `float#`, an unboxed float type that lives in registers, and `let mutable` for stack-allocated mutable variables. Together, they let you write inner loops where the accumulator never touches the heap: module F = Stdlib_upstream_compatible.Float_u let[@inline] imdct_long input = for i = 0 to 35 do let mutable sum : float# = F.of_float 0.0 in for k = 0 to 17 do let cos_val = F.of_float (Float.Array.unsafe_get cos_table (i * 18 + k)) in let inp_val = F.of_float (Array.unsafe_get input k) in sum <- F.add sum (F.mul inp_val cos_val) done; Array.unsafe_set output i (F.to_float sum) done These kinds of optimisations got me from 2.35s down to 2.01s. What I felt was missing was an accessor function which returned an unboxed float from a floatarray, so I wouldn’t need to unbox with `F.of_float`. However, I couldn’t find it. The httpz parser really benefited from OxCaml’s unboxed types because its hot path operates on small unboxed records that stay entirely in registers: #{ off: int16#; len: int16# } # Results The optimisations brought a 29.5s MP3 decoder down to 2.01s. Mostly through standard OCaml optimisations, but OxCaml’s `float#` saved another ~14%. Decoder | Time | vs ffmpeg ---|---|--- ffmpeg | 0.74s | 1x LAME | 0.81s | 1.1x ocaml-mp3 (original) | 29.5s | 40x ocaml-mp3 (Hashtbl) | 6.4s | 8.6x ocaml-mp3 (flat + fast bitstream) | 3.5s | 4.7x ocaml-mp3 (best) | 2.4s | 3.2x ocaml-mp3 (OxCaml) | 2.0s | 2.7x
Moritz Hamann
@moritzhamann.com

Finally got the time to play around with Apple's local LLMs (Foundation Models). So far it's a mixed bag: It's able to answer questions about articles but needs precise prompting and the context window is only ~4.1k tokens, so not much will fit.

Moritz Hamann
@moritzhamann.com

However, the most annoying part is by far is that it sometimes just refuses to produce an output due to safety reasons. This even happened when asked about details of news articles.

Moritz Hamann
@moritzhamann.com

just tried gemini to vibe some zig, but the recent redesigns around io interfaces and the frequent changes in the stdlib due to being < 1.0, made this a rather frustrating experience. On the other hand it's a good way to actually learn zig by fixing all the compilation errors ...

Moritz Hamann reposted

antirez
@antirez.bsky.social

I have had enough of Telegram services run by unknown individuals to do the audio transcription task in my Telegram channels. Wrote one using my botlib, ffmpeg and whispher.cpp. May be useful for you as well, perhaps? github.com/antirez/whis... Transcription quality is WAY better.

github.comGitHub - antirez/whisperbot: Telegram bot that transcribes audio messages via whisper.cppTelegram bot that transcribes audio messages via whisper.cpp - antirez/whisperbot
Moritz Hamann
@moritzhamann.com

I love how LLMs make it so easy to customise my neovim now. Tiny little scripts that either replace existing plugins or add very specialised workflow enhancements. Just wrote a 100 line function that adds a zen mode with backdrop. Still had to tweak the result, but 95% was basically there

Moritz Hamann reposted

srrrse
@without.boats

Replying to @without.boats

I have included the most relevant section in the alt text of this image of him giving the talk:

Moritz Hamann reposted

konnaire
@konnaire.bsky.social

Everybody thinks 'https://' stands for 'hypertext transfer protocol secure' but it actually stands for 'head to this place, sucka' followed by a colon and two laser sounds

Moritz Hamann reposted

Sergey Tihon 🦔🦀
@sergeytihon.com

I'm still looking for 10 more #fsharp lovers to fill out the #FsAdvent schedule. 🙏

Sergey Tihon 🦔🦀@sergeytihon.com

F# Advent Calendar in English 2025 #fsharp #FsAdvent sergeytihon.com/2025/11/03/f...

sergeytihon.comF# Advent Calendar in English 2025🎄 It’s that magical time of year again! 🎅🏻Christmas is twinkling on the horizon, and that means one thing — it’s time for the 12th annual F# Advent in English! It’s incredible to think that our tra…

Moritz Hamann reposted

antirez
@antirez.bsky.social

When you use coding agents for something that produces the bulk of the code of an application that will be used for years, also factor in the technical debt that you are happily accumulating. When you use LLMs an an aid, you could, on the contrary, improve your coding culture.

Moritz Hamann
@moritzhamann.com

After trying to pick up Go again, I'm more convinced that it should have a .? operator or at least some linter rules to enforce nil checks on pointer receivers. This would stuff like `myVar.GetX().GetY()` (where GetX/Y returns pointers) at least a bit more safe ...

Moritz Hamann
@moritzhamann.com

Trying now for hours to figure out why and when Safari on macOS is rendering "font-family: fantasy" either as Zapfino or as Papyrus, but don't have the slightest idea so far...

Moritz Hamann
@moritzhamann.com

www.seangoedecke.com/not-your-cod... This resonates quite a bit with me. The best advice I've ever seen was from a Jane Street tech talk about their internal code review practices (encouraging reviewers to push to the branch rather than just leaving comments bsky.app/profile/mori...)

seangoedecke.comIt's not your codebaseEngineers often feel a lot of ownership over the code they write. That’s understandable: it’s partially their creation, and it’s also their workspace, so they…
Moritz Hamann@moritzhamann.com

I think the takeaway from this quote has changed my view on code reviews forever: "When I’m working on a branch, it sort of feels like this is my feature. [...] when other people push to it, [...] that goes away. [...] which is good. I mean, all code becomes someone else’s eventually"