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?

Nvidia Stock Ski Jump

Ask HN: Are companies making money by using AI?

A personal website disguised as a retro spacecraft console

Trump Says He Told AI Executive to Kiss His Family Goodbye Before Going to Jail

Brigade

I built an open-source Python tool to download YouTube videos

Australia to introduce mandatory incident reporting after OpenAI hack

Ontology #2: wish you were here

Stingray Fish Laser

AI Second Brain Masterclass [video]

California voters reject measure to tax the wealth of billionaires

Show HN: ZTHR – what replaces code review when AI agents write all the code

Notes on Fable 5.2

CoreWeave bond yield tops 16% as AI credit stress rises

Slack bot can now generate its own UI on demand

Charleston AI

QNet: Post-quantum Layer-1 in Rust using native ML-DSA-65 signatures

Show HN: Kinsona – a hotel booking site that shows its cut on every booking

Show HN: AI Frothiness Index. Daily reading of how stretched the AI boom is

Sheet Music Deserves Better, So We Built Our Own Company [video]

Microsoft patent: turning idle gaming GPUs into paid AI training hardware

Cult of the Dead Cow Reboot [Apr 2026]

Guns on Amtrak Trains? A Workers Union Is Up in Arms.

Daybreak says I'm all set. Codex still blocks my own security audit

Nvidia's AI advantage is moving beyond the GPU

$16k and a Solar Panel

Debloat Any Android or Google TV over Wi-Fi

Serc: CPython bytecode compiler written in Rust (2-4x speedup, Codex built)

OpenAI models have no agency anymore

ASRock Rack DMRD16-2L+ Spotted with 16 DDR5 Slots for Diamond Rapids