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?

Foundations of Metrology(1981) [pdf]

Show HN: Self hosted video feed for children

Open Source Does Not Imply Open Community

James Broadnax Executed After Being Sentenced to Death Based on Rap Lyrics

Where would an offline fail-closed supervisor be useful?

CSS and vertical rhythm for text, images, and tables

Sniffing EU Smart Meters with a Flipper Zero (WM-Bus / 868MHz)

GlowGoblin – a gift to mb pro users

Japan intervened in its Curreny price

US telecom agency votes to expand tech crackdown on China

Anthropic Model inference runs fastest on AWS

How People ask Claude for personal guidance

No action taken against PimEyes: noyb lawsuit against Hamburg DPA

The Starlink hack that doomed Russian troops [video]

Insights into software job openings – may2026

Shivon Zilis Operated as Elon Musk's OpenAI Insider

Japan Airlines begins humanoid robot trials at Tokyo's Haneda airport as labor s

Elon Musk Seemingly Admits xAI Has Used OpenAI's Models to Train Its Own

LA-SF rail will cost about $126B, with service beginning around 2040

Show HN: Git repositories hosted directly on Freenet

U.S. Aims to Penalize Disabled Adults Who Live with Their Families

AliothPress – self-hosted, cloud-native CMS with a wizard-based installation

One solar storm could trigger a catastrophic collision in orbit

Show HN: A vdom-less framework that's local first

AI Tips and Tricks

Show HN: ChatToMap – Scans your chats to find all your activity and trip ideas

Kolmogorov Complexity [video]

10x Faster Real-Time High-Quality AI Video Generation

LLM Summaries Are Ruining Your Learning

AI and the Future of News 2026