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?

In the search for an e-paper tablet in 2026

Rapid Hot-Swapping for Go Lambdas

Show HN: A read-it-later app that exports clean Markdown to Obsidian

The nostalgic winter drink dividing Germany

Anthropic's AI Coding Study: How You Use AI Matters More Than Whether You Use It

Is traditional ML relevant anymore? Any active research going on in ML methods?

Hyping an Editor in the Age of AI

Intel Foundry boss leaves for Qualcomm

Show HN: Leviathan, A world where AI agents write the laws and govern themselves

Swift System Metrics 1.0

The normalization of corruption in organizations (2003) [pdf]

Leaving AI to Code 24/7 Doesn't Work

Build dynamic agentic workflows in Opal

Show HN: PipelineIQ – AI diagnoses CI/CD failures and sends fixes to Slack

Techniques of Neutralization

All the troubles of the world by Isaac Asimov [pdf]

Agentic Engineering Patterns

Measuring CPU Load

Boston Review: A Brief History of AI Psychosis

Show HN: Arrival Radar

How AI will change GTM?

Show HN: Export Your YouTube Subscriptions to OPML (and Use Any RSS Reader)

When the Bubble Bursts

Spatial AI-native graph workspace

Show HN: MotionDesk: Physics-driven, Metal-accelerated wallpapers for macOS

Show HN: Nano Banana 2 – Sub-second AI image gen via Gemini 3.1 Flash

Show HN: Conduit – Automatic Port Forwarding for Docker Containers

RFC 9925: Unsigned X.509 Certificates

I used Claude AI to build this website that shows upcoming indie game festivals

Chivalry Test