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?

Europe's warm nights nearly doubled this summer

Anyone Got a Fenty.dev Invite?

The Distractor

Show HN: Clownbid.lol – pay to be the biggest clown on the internet

Give Your Coding Agent a Journal

If You Knew God Exists, Wouldn't You Become a Priest?

Are We Learning to Think Less?

The Ternus Era at Apple Begins, but Cook Isn't Leaving

Will anybody use AI as much as coders?

Show HN: Break 5, the addictive, 5 minute, daily word game

West Point prof fired for continuing to teach human causes of climate change

Israel Is Running a Synthetic Think Tank to Influence AI Search Results

Show HN: Open-source hands-free mouse control with Tracky Mouse

Debian developer resigns after corporate LLM use without disclosure wins vote

Papers with wrong IDs on ArXiv more common

Show HN: St. Louis Food Map

Building software factories (with no slop)

Packman package manager to be discontinued on 2026-12-31

"A big win for Android interoperability"

Lady Gaga is now an AI-longevity biotech founder

The tests passed. The extension was still broken

No-Code Self-Documenting Makefiles

Show HN: What Apple's OS updates silently change in the on-device AI model

How to build a diffusion language model

The Aviation Herald was sued

Show HN: I timestamped 34 trading strategy sweeps before running them

Matrox: Graphics for Professionals

California Passes AB-1856 for Open-Source Relief over Age Verification

Generating scenarios for extreme events, without extreme data

Accidental Aesthetics and Romance of Power Wires: Infrastructure Is Sexy