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?

Why the Cookbook Endures

Electric air taxis are stuck in the courtroom

Backporting bug fixes is dead, Project Valkey now sends in the bots

Linux '95

Vulgar Materialism

Show HN: Teach your kids absolute (perfect) pitch

Printing Gaussian Splats

Show HN: TermType – a terminal typing game where words fall like Space Invaders

Anthropic to Require ID Verification for Certain Capabilities Starting July 8

Why Mizoram has shops without shopkeepers (2024)

Show HN: A GitHub app that suggests code fixes for conversion failures

Smashing the NIMBYs created modern capitalism

Safe SIMD in Rust, Even on the Inside – By Sergey "Shnatsel" Davidoff

Why do sports stadiums have different names for the World Cup? Here's the reason

Neosolve – SolveSpace fork with OpenCASCADE CAD kernel

Creativity in the form of archived web pages from the dawn of the internet

How the social media ban could reshape how all of us use the internet

Where the sun stood at the 2026 summer solstice

Solvespace Web Version

Developer ends Fornjot (CAD kernel) development

Ask HN: Future of Programming?

Pakistan: The solar revolution nobody planned

Rent Is So High, New Yorkers Are Living with Nuns

Huffman tree compressor and decompressor written in Clojure

Masochistic YouTuber Punishes Himself by Writing a First Person Shooter in COBOL

AI Made Me Braver

Local Inference

Tokoscope – Automatic LLM token compression and cost monitoring in 2 lines

A viral doomsday scenario aims to shake Europe out of its AI complacency

Counterfactual Quantum Computation