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?

Life Is Short (2016)

Grimm Brothers' Children's and Household Tales (Grimms' Fairy Tales)

Hello, Ordinary Blog

Phloto for My Photo Flow

MiniMax teased M3 Sparse Attention: 9.7x prefilling, 15.6x decoding at 1M

My First Web App for Monetization

Iran president ends Internet blackout, orders access to be restored

A Dose of Hope for the Future

Ask HN: Has AI affected negatively the job market for devs?

Google I/O 2026: Sundar Pichai's opening keynote

Ask HN: Sudden spike in web traffic 19-21 May?

Pieces

Scientists Found a New Type of Crystal Formed by the First Nuclear Explosion

Huawei touts chip design breakthrough in bid to defy U.S. sanctions

An old interview of Dijkstra (1985)

Workspace Intelligence

Family tree and org chart react lib

Private 5G, Agentic BSS and Starter Kit Demos

Accounting tools are built for accountants, not the rest of us

Drones crash into Sydney harbour after light show glitch

EarnOS – brands reward users for real attention, not bot traffic

Duolingo is experiencing increased errors

NASA unveils next steps to build permanent Moon base

Show HN: I built a tool to auto-accept AI slop and bigtech devs loves it

The Social Contract of Writing

OpenAI admits AI hallucinations are mathematically inevitable (Sept. 2025)

BadHost: One Char Bypasses Host-Based Security Across the Python AI Stack

Disclosing the Badhost Vulnerability in Starlette

Micron hits $1T market cap for the first time

From AFSK to Goertzel: demodulating packet radio