Packed Data Support in Haskell

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

77•matt_d•12mo ago

Comments

nine_k•12mo 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•12mo ago

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

Zolomon•12mo ago

They mention this in the article.

spockz•12mo ago

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

cstrahan•12mo ago

No, one example of why being variable sized integers.

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

carterschonwald•12mo ago

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

tlb•12mo 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•12mo 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•12mo 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•12mo ago

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

lordleft•12mo ago

This was very well written. Excellent article!

NetOpWibby•12mo ago

Is this like MessagePack for Haskell?

Fashion for a Hot Planet

Thunderbird Pro April 2026 Update

Xiaomi MiMo-v2.5 is now officially open-sourced

Show HN: macOS screensaver that displays Google Trends as fish in a deep-ocean

Ask HN: What Is the "Lore" of HN?

Show HN: CoPilot for Project Management

Compu-Global-Hyper-Mega-Net: A Retro Internet for Retro Computers (LFNW 2026) [video]

A man who decides when and where your next flight will be going

Event Clash of Prompts: A Real-Time Prompt Battle Royale

Another supply-chain attack: elementary-data Python package compromised

Live coverage: ULA to launch 29 Amazon Leo satellites on Atlas 5 LIVE in ~2hrs

Immigrants' Recent Effects on Government Budgets: 1994–2023

Talkie: a 13B vintage language model from 1930

Ask HN: Will hardware ever be cheap again?

Talkie: An LM from 1930

ChatGPT Images 2.0 Still Can't Draw the Seven-Legged Spider I Want

AMD used AI to reimplement slurm in Rust

Trump Administration Will Pay More Energy Firms to Cancel Wind Farms

OlmoEarth: Custom embedding exports for downstream analysis

Using Rust to Build a $1 Handheld Gaming Console

David Silver of DeepMind raises $1B to build AI that learns without human data

Gitglimpse – a CLI that turns your Git history into structured context

California's Billionaire Tax Has the Signatures to Make the Ballot

Switched from robot_localization to a single-node GPS fusion setup

Tell HN: Spam from Fridayaicore.in

A History of Live Programming (2013)

AI strategy is all wrong

It's the Age of Electricity and America Isn't Ready

Noctua releases official 3D CAD models for its cooling fans

Tell HN: One Medical Is a Nightmare