Packed Data Support in Haskell

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

77•matt_d•7mo ago

Comments

nine_k•7mo 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•7mo ago

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

Zolomon•7mo ago

They mention this in the article.

spockz•7mo ago

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

cstrahan•7mo ago

No, one example of why being variable sized integers.

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

carterschonwald•7mo ago

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

tlb•7mo 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•7mo 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•7mo 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•7mo ago

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

lordleft•7mo ago

This was very well written. Excellent article!

NetOpWibby•7mo ago

Is this like MessagePack for Haskell?

A customizable agentic AI toolkit for e-commerce

What happens when you add a new Teller?

I built a browser tool that converts ANY file → Markdown

Is GitHub Down?

Twin suction turbines and 3-Gs in slow corners? Meet the DRG-Lola

Two Elegant Use Cases for Go Build Tags

TikTok will let users share feeds in DMs

I miss the old Qasar, not the new Qasar

I Built a Rolling Collector to Grab X Threads for AI

The Abundance Paradox: Why Netflix's Acquisition Makes Sense in the Era of AI

China's ZTE may pay over $1B to the US over foreign bribery allegations

Google Stitch

AI Predictions for 2026: A DevOps Engineer's Guide

Mrva: Terminal-first approach to CodeQL multi-repo variant analysis

Craft software that makes people feel something

Stop Hoarding Tasks Like They're Canned Peaches for the Apocalypse

JPMorgan: The biggest national security threat may be America's workforce

Pop-out car door handles could disappear for good

Show HN: Firefly Forest

Show HN: Snapalabra (Learn language through images)

French supermarket's Christmas advert is worldwide hit (without AI) [video]

Ayaneo Pocket Play – A Gaming Phone with the Soul of a Handheld [video]

Show HN: JotBird – A simple Markdown editor with one-click publishing

Launch: Bubs AGI OS – A Personal AGI Operating System (Founders Presale)

$27,000 a Year for Health Insurance. How Can We Afford That?

Microscopic robots that sense, think, act, and compute

Social Channels in Search Console

Why No Fish Wants a Tongue-Eating Parasitic Louse in Its Mouth

Practical Tips for Gemini 3

Why Google Stores Billions of Lines of Code in a Single Repository