Packed Data Support in Haskell

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

77•matt_d•9mo ago

Comments

nine_k•9mo 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•9mo ago

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

Zolomon•9mo ago

They mention this in the article.

spockz•9mo ago

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

cstrahan•9mo ago

No, one example of why being variable sized integers.

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

carterschonwald•9mo ago

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

tlb•9mo 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•9mo 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•9mo 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•9mo ago

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

lordleft•9mo ago

This was very well written. Excellent article!

NetOpWibby•9mo ago

Is this like MessagePack for Haskell?

Show HN: Konform Browser v140.7.0-108

Structure Beats Prose: Specs for Coding Agents That Work

Design is dead, it's all evolution now

Mistral.rs – Fast, zero-config multimodal LLM inference for a variety of models

Benchmarking Claude C Compiler

What Moltbook alternatives are doing some actual constructive work?

Show HN: PhoneClaw

Towards a Standard for JSON Document Databases

Brutalist Southbank Centre Listed

Sandboxing Systemd Services

Ask HN: Starting my own startup to increase compute density

Linux USB iPhone Tethering

Why the Internet Is Terrified of London

AI Coding Is a Framework–Use It Like a Library

A one-prompt attack that breaks LLM safety alignment

Subscription plans for YouTube TV are now cheaper

Show HN: YAML-based security framework for CDN edge (CloudFront / Cloudflare)

How to Keep What You Built Together

Composer 1.5

A few design decisions for a new chat platform

Show HN: Canon-C – a semantic C library

Ask HN: How do you maximize your luck surface area?

Show HN: Local-first bookmark app for files, folders, and websites

Show HN: Pincer-MCP – Stop AI agents from reading their own credentials

Fiorello La Guardia and the Making of Modern New York

Are we in an AI Bubble? A researched thesis detailing both sides.

How Oura Ring Won over Washington

A16Z-backed super PAC is targeting Alex Bores

Any public labeled dataset of (customer question → seasoned sales response)?

Can you rewire your brain?