Packed Data Support in Haskell

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

77•matt_d•10mo ago

Comments

nine_k•10mo 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•10mo ago

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

Zolomon•10mo ago

They mention this in the article.

spockz•10mo ago

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

cstrahan•10mo ago

No, one example of why being variable sized integers.

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

carterschonwald•10mo ago

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

tlb•10mo 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•10mo 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•10mo 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•10mo ago

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

lordleft•10mo ago

This was very well written. Excellent article!

NetOpWibby•10mo ago

Is this like MessagePack for Haskell?

Ask HN: Is Another Editor Needed?

Chern Number

Megadev: A Development Kit for the Sega Mega Drive and Mega CD Hardware

PowerSchool: Entry vs. Execution

'You are all worse than each other': anti-regime Iranians turn on Trump

Fooorma: Open-Source Procedural Art Studio

China 15th 5 Year Plan (Official English Translation)

Age Verification Lobbying: Dark Money, Model Legislation, Institutional Capture

Ask HN: How do you guys deal with enshittification mentally?

James Nachtwey: War Photographer (2001) [video]

Chinadocs: Public Database of Official Gov Documents of PRC

Show HN: TriGame – Guess the area of a triangle made by cities

Underwater data center powered by tidal energy proposed off the coast of Maine

Show HN: Connections Game in 195 Languages

Psi-Commit – Cryptographic Commitments Anchored to Bitcoin via OpenTimestamps

Room 641A

Show HN: HN Buddy – a Hacker News Chrome extension

LearnCro Mobile and web application for learning the Croatian language– level B1

Send a Beautiful Digital Bouquet

Show HN: Markitdown in Go

Show HN: ProjectFalcon – First Native Java at Protocol Implementation

Give Agents Maximum Freedom. The less you assume, the more it works

Star Wars Bounty Hunter Names – Mercenary Name Guide and Generator for Fans

Show HN: Vector databases are the wrong primitive for AI agents

Introducing, the British Cræft Prize

Autoresearch Hub

Ask HN: What newsletters do you read every day or week?

State Department slashes fee to renounce US citizenship by 80%

A self-hosted intelligence terminal that watches the world for signals

Show HN: One MCP server that gives your AI agent access to 25,000 tools