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?

The Age of Eerie A.I. Political Ads Is Here

Sunsetting Code with Me

Show HN: HiLo – A word guessing game based on binary search

How I use crit to build crit

Ask HN: AI Agents vs. Gateways vs. Harnesses

Hackmate – a side project I built last year to help builders find collaborators

Horizon redress still a mess, MPs say – and Fujitsu hasn't paid a penny

Alaska sues GoFundMe, others over unauthorized charity pages

Show HN: DataCia – The database client that lets you focus

Ogham MCP – Shared memory for AI coding agents, backed by Postgres

Home Care

Testing Universal Poster v10

Show HN: HighSNR – Cut length and noise from your LLM context

The Self-Deceived Liar

Project Canard: $96 3D-Printed guided MANPADS rocket with MPU6050 and ESP32

Agile ain't as bad when done by clankers

Paul R Ehrlich has died

Construct of the Day

I Simulated 38,612 Countryle Games to Find the Best Strategy

Show HN: AI agent autonomously used BoTorch to predict CFPB enforcement actions

Corruption erodes social trust more in democracies than in autocracies

I Love FreeBSD

West Sussex's Oracle rollout pushed back again as costs balloon 15 times

AI Unicorn ElevenLabs Is Making a $1B Effort to Restore 1M Voices

Operation Hormuz (1989)

Open source Chrome extension to customize Veesion alert notification sounds

Scientists discover a surprising way to quiet the anxious mind (2025)

20 Years of Amazon S3

Meta up 3% in premarket as it plans mass layoff amidst increased AI spending

Show HN: Merrilin.ai – Code blocks in your books, finally