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?

A volunteer stopped a backdoor from exposing Linux systems worldwide (2024)

RecallDock

Europe would not be able to sustain war of attrition with Russia

A very old Blog?

Fiber-immersion microfabrication with sub-10µm resolution for under $300 [video]

Hwaro – A Lightweight and Fast Static Site Generator Written in Crystal

A Wiki for AIs

Any Nix package, live in your browser

Using Blender with coding agents on macOS

Ask HN: Would you read a statistics textbook?

Show HN: Move Claude Code sessions between accounts in Claude Desktop

Lists of Problems

Clean up your Android TV

Decapitating a MacBook

Care for a Little More AI?

WeatherNext 3: Hourly global weather forecasts using live satellite data

Thank you for being part of the GitHub Classroom journey

Show HN: Octoweb – a free, open-source keyboard-first browser for macOS

VS Code – Official Documentary [video]

I Want More AI at Dartmouth

The Dark Side of Mindfulness

Teaching robots mortal kombat moves [video]

The state of AI in 2026: On the road to ROI

Judge blocks X rival from using Twitter name, but allows 'Tweet' for now

Is your favorite plant-based milk good for the planet

Seismic Isolation

34 arrests made for drug trafficking at Burning Man as of Friday

Vancouver strip club's Instagram taken down over sign featuring lake joke

Datacenters Are the New Shale Oil

Show HN: Generate safe WebMCP tools from your OpenAPI spec or validation schemas