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?

How I Work

Kagi Small Web

A Single Cobalt Shock Could Trigger Global EV Battery Supply Chaos

The frontier is open-source today

Hand-powered LLM (YouTube) [video]

Every DFU Button Is a Failure

Palmier-pro: macOS video editor built for AI

Venice proposes hiking entry fee to €50

Show HN: Lil Apps

Evaluation order and nontermination in query languages

Claude is your insider threat now – Dan Tentler – Security Fest 2026 [video]

Do Elite Universities Overpay Their Faculty?

Cuba to Privatize State Companies

Do weird corporate governance structures work well?

Let an Agent run the apps on your computer

Iran says it's closing Strait of Hormuz, accusing Israel, US of violating truce

Ribbie, Live Baseball in Pixels

Letheo – a Cognitive Runtime for agent memory in Rust (forgetting by physics)

Homo Agenticus

How to Lose a Global AI Monopoly in One Afternoon [video]

Tesla's self-driving safeguards fooled by $30 doll heads

Eliya – a compliance-focused OpenJDK 25 distribution (Phase 1 of a JVM platform)

Cotect – a fast code inspector for the agent era

FCC Seeks Comment on Enhanced Know-Your-Customer Requirements

Epidurals Are a Miracle Technology

Write a Letter to Your Future Self

Sinceerly, AI to undo your AI writing

Granta stops publishing short story award winners over AI controversy

Show HN: Video on the map marketplace 1 year – still bad traction

Hyperia 0.12.7 is released: an agentic terminal for agents and humans