Packed Data Support in Haskell

https://arthi-chaud.github.io/posts/packed/

77•matt_d•10mo ago

Comments

nine_k•10mo ago

> Introducing the ‘packed’ data format, a binary format that allows using data as it is, without the need for a deserialisation step. A notable perk of this format is that traversals on packed trees is proven to be faster than on ‘unpacked’ trees: as the fields of data structures are inlines, there are no pointer jumps, thus making the most of the L1 cache.

That is, a "memory dump -> zero-copy memory read" of a subgraph of Haskell objects, allowing to pass such trees / subgraphs directly over a network. Slightly reminiscent of Cap'n Proto.

90s_dev•10mo ago

We are always reinventing wheels. If we didn't, they'd all still be made of wood.

Zolomon•10mo ago

They mention this in the article.

spockz•10mo ago

It reminds me more of flat buffers though. Does protobuf also have zero allocation (beyond initial ingestion) and no pointer jumps?

cstrahan•10mo ago

No, one example of why being variable sized integers.

See https://protobuf.dev/programming-guides/encoding/

carterschonwald•10mo ago

One thing that sometimes gets tricky in these things is handling Sub term sharing. I wonder how they implemented it.

tlb•10mo ago

> the serialised version of the data is usually bigger than its in-memory representation

I don’t think this is common. Perhaps for arrays of floats serialized as JSON or something. But I can’t think of a case where binary serialization is bigger. Data types like maps are necessarily larger in memory to support fast lookup and mutability.

nine_k•10mo ago

I suppose all self-describing formats, like protobuf, or thrift or, well, JSON are bigger than the efficient machine representation, because they carry the schema in every message, one way or another.

IsTom•10mo ago

If you use a lot of sharing in immutable data it can grow a lot when serializing. A simple pathological example would be a tree that has all left subtrees same as the right ones. It takes O(height) space in memory, but O(2^height) when serialized.

gitroom•10mo ago

honestly i wish more stuff worked this way - fewer hops in memory always makes me happy

lordleft•10mo ago

This was very well written. Excellent article!

NetOpWibby•10mo ago

Is this like MessagePack for Haskell?

A robot arm with puppy dog eyes is just one of Lenovo's new desktop AI concepts

Parallel coding agents with tmux and Markdown specs

Service Down? Your Notch Will Tell You

Our Design Docs Write Themselves

Show HN: Clean Express – NNTP/Usenet Client for iOS/macOS/visionOS

Running Mainline Linux, U-Boot, and Mesa on Rockchip: A Year in Review

We fixed a critical auth bypass in Cloudflare's AI-generated Next.js

How AI is reshaping developer choice (and Octoverse data proves it)

How does AI detection work?

Hackerbot-Claw: An AI-Powered Bot Actively Exploiting GitHub Actions

Show HN: MoodJot – Mood tracker mobile app with community feed, built with KMP

Forestry England to see 'increased number' of renewable schemes

The Legibility Problem

Show HN: Predicate-Claw – Run Time Assurance (RTA) for OpenClaw via Rust Sidecar

Codex built my startup in a weekend

Show HN: Vynix – Mobile app with 100 AI models for image/video/audio generation

A 3D simulator, visualizer and replayer for Drones

Adding "Log in with Mastodon" to Auth0

Ask HN: If you interview an LLM for SE position, what would be your placement?

Elevated Errors on Opus 4.6

Show HN: Grok Imagine 2 – A preview of the next-gen Grok AI video ecosystem

How does B-tree make your queries fast?

Ask HN: Freelancer? Seeking freelancer? (March 2026)

Word Map – A Game About Hill Climbing and Stepping Stones

Notes on Lagrange Interpolating Polynomials

Vend-O-Vision: Trading Quarters for Watching TV in Public

Ask HN: Who is hiring? (March 2026)

Ask HN: Who wants to be hired? (March 2026)

Show HN: Open-source Loom / Screen Studio with editing and auto-zoom

One-Bit Delay