Packed Data Support in Haskell

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

77•matt_d•1y ago

Comments

nine_k•1y 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•1y ago

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

Zolomon•1y ago

They mention this in the article.

spockz•1y ago

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

cstrahan•1y ago

No, one example of why being variable sized integers.

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

carterschonwald•1y ago

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

tlb•1y 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•1y 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•1y 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•1y ago

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

lordleft•1y ago

This was very well written. Excellent article!

NetOpWibby•1y ago

Is this like MessagePack for Haskell?

You Won't Finish This Article

More people around the world now favour China over the US, Pew study suggests

Archer Announces Zee, AI Foundation Model Purpose-Built for Aviation

I'm early in my career and built an honest job-search agent for senior engineers

Nick Shirley Delivers his Testimony at the Senate Committee Hearing – 7/15/26 [video]

Ask HN: Are AWS Certs worth getting for experienced Devs?

Mixture of agents is obsolete, Meet MOD

Show HN: Pgmig: Generate migrations between Postgres databases

Algo Framework Stress Tester

Mass. startups raised nearly $5B last quarter, regaining lead over Texas

Ask HN: Are the heaviest AI users of your team blowing past everyone else?

India to allocate $20B to semiconductor and smartphone manufacturing

3D-printed bridge points the way to greener construction

Funding Signals – an API that finds companies the moment they raise money

The Explosive Diarrhea Outbreak Is About to Get Much Bigger

Show HN: Collaborate.dev – Multiplayer Visual Desktop for Coding Agents

Show HN: Benchmarklist: track AI benchmarks (2.4k+), models, and capabilities

Hacker Fables – A satirical cyberpunk novella you can read as a man page

What If the Harness Comes Before Pretraining? A Data Flywheel Perspective

So long r/rust, and thanks for all the Slop!

Show HN: Betula Fuzzy Search

Mimesys: Turn Resource Usage Traces into Executable Workloads

Alman: German, Simplified

Murati's Thinking Machines Releases Open-Weights 975B Parameter LLM

Disposable Software

C Strings: A 50-Year Mistake – By Trần Thành Long

Sorel Caribou Boots: Great Product, Disappointing Online Shop

Inkling: Our Open-Weights Model

Odyssey Linux – a Void-based distro trying to make no-systemd approachable

Show HN: How you auto recover your Claude Code workflow when quota resumes