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?

Micro-Front Ends in 2026: Architecture Win or Enterprise Tax?

Japanese rice is the most expensive in the world

These White-Collar Workers Actually Made the Switch to a Trade

The Wonder Drug That's Plaguing Sports

Show HN: Which chef knife steels are good? Data from 540 Reddit tread

Federated Credential Management (FedCM)

Token-to-Credit Conversion: Avoiding Floating-Point Errors in AI Billing Systems

The Story of Heroku (2022)

Obey the Testing Goat

Claude Opus 4.6 extends LLM pareto frontier

Brute Force Colors (2022)

Google Translate apparently vulnerable to prompt injection

(Bsky thread) "This turns the maintainer into an unwitting vibe coder"

Software development is undergoing a Renaissance in front of our eyes

Can you beat ensloppification? I made a quiz for Wikipedia's Signs of AI Writing

Spec-Driven Design with Kiro: Lessons from Seddle

Agents need good developer experience too

The Dark Factory

Free data transfer out to internet when moving out of AWS (2024)

Interop 2025: A Year of Convergence

Prejudice Against Leprosy

Slint: Cross Platform UI Library

AI and Education: Generative AI and the Future of Critical Thinking

Maple Mono: Smooth your coding flow

Moltbook isn't real but it can still hurt you

Take Back the Em Dash–and Your Voice

Show HN: 289x speedup over MLP using Spectral Graphs

Teaching Mathematics

3D Printed Microfluidic Multiplexing [video]

Abstractions Are in the Eye of the Beholder