Packed Data Support in Haskell

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

77•matt_d•9mo ago

Comments

nine_k•9mo 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•9mo ago

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

Zolomon•9mo ago

They mention this in the article.

spockz•9mo ago

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

cstrahan•9mo ago

No, one example of why being variable sized integers.

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

carterschonwald•9mo ago

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

tlb•9mo 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•9mo 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•9mo 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•9mo ago

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

lordleft•9mo ago

This was very well written. Excellent article!

NetOpWibby•9mo ago

Is this like MessagePack for Haskell?

A 2.5x faster Postgres parser with Claude Code

The age of a treacherous, falling dollar

The End of Human Relationships

I built a digital safe with multiple keys after a few too many bike concussions

The Assault on Ukraine's Power Grid

Where Drupal Still Wins in 2026?

Tesla likely can't escape 'Blade Runner 2049' lawsuit

A tale of three kings (Python, Elixir, Go) (2017)

Don't Look Behind the Curtains

Show HN: Ironpad – Local-first project management with Git versioning

Irony alert: Anthropic helps UK.gov to build chatbot for job seekers

Consider F# (2024)

The times Yann LeCun has been wrong about LLMs

Crazy shit linkers do: Common Data (COMDAT) sections

Ask HN: Resources on how and why these LLM's work

Competence as Tragedy

Unleash endless fun with Baent Games

HarfBuzz at 20

Find the lowest prices on prescription drugs

New in /experimental mode in Copilot CLI: "Fleets"

System Initiative Shutting Down

Elon's tech tree is converging

From Roots to Reach: Network Resilience in Natural Disasters

Gokin: Go-Native CLI for AI-Assisted Coding with Gemini, DeepSeek, GLM, Ollama

Macau's Grand Emperor hotel rips up lobby floor to sell off gold bricks

I used Gemini to build an all-in-one Chrome extension, and uninstalled 10 others

Is C-rating marketing, or does it still matter for LiPo packs?

Show HN: TurboLibBMP 0.1.1 – single-header BMP in C (no allocations, embedded)

Serenity Prayer

Jeffrey Epstein Interview [video]