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?

Dawkins, Claude and the Myth of Consciousness in Artificial Intelligence

Ask HN: Ten Yrs from now, when only AI codes, what's the stack?

Programming in 2026: excitement, dread, and the coming wave

Store Tags After Payloads

Show HN: Docx-CLI – let agents edit your Word files safely

Show HN: Zift – find authorization logic in your code

RAG retrieves the refutation and still gets it wrong

Sendapi.co – One API for WhatsApp, SMS, and Email

Why some mathematicians think we should abandon pi

LaDiR: Latent Diffusion Enhances LLMs for Text Reasoning

YouTube, your RSS feeds are broken

AI and That Guy at the Bar

Copy.fail: a small Linux kernel bug with an unusually big blast radius

Peter Thiel backs $1B ocean data centre startup powered by waves

Startup Ignites First Fusion Rocket

Folie à Deux: The most dangerous hallucination is one you're inclined to believe

An AI use policy generator that outputs a deployable managed-settings.json

What AstralCodex Gets Wrong about Argument Maps(In the Voice of Scott Alexander)

UpScout – Fast, multi-region uptime monitoring built in Rust

Puter 26.05

Show HN: I vibe coded a free site blocker

What Happened to Notre Dame's 180k Bees? (2019)

Don't Become an Agent Wrapper

Show HN: QA-recorder – One-click QA reports for web apps

Ask HN: The death of software development as a job?

ZooL4nD3r: Translate a passage across 961 learned discourse communities

Ask HN: What Are You Building?

Now Available: Monthly Subscriptions with a 12-Month Commitment

Trader.ai – a leaderboard of AI trading bots you can learn from

Microsoft is hiding Windows 11's 'eyes'