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?

Filmgrab: Films A-Z

Why do people hate the tech industry? (2023)

Midnight social media curfew proposed for UK teens aged 16 and 17

Prioritize mental health, and why communication is so important

Show HN: For 10 World Cups, my model's 2 favorites had the champion every time

Xmark: Chat with your saved X bookmarks

I reverse-engineered the three biggest agent-memory tools

Show HN: Update on my media editor in browser no back end

Physicists Have Argued over This Problem Since 1883. It May Now Be Solved

Show HN: Browse, search, stats, skills from your Claude/ChatGPT chats, locally

HyWiki: Zero Markup Hypertext

GLNBench – Benchmarked GNNs under label noise and found they collapse

Projected Business Formations Within Four Quarters: Professional Services in US

My Custom Life OS Software

Microsoft Reports a 25 Percent Jump in Emissions

A man who would change Russia

Weathergotchi – an open-source climate Tamagotchi

How much of ML research is about AI safety, what is it about, and who's doing I

Floating Companion: Exploring Design Space for Soft Floating Robots in Indoor

Show HN: Prijm – a minimalist link-sharing and discussion platform

Fylepad – Thoughtful, secure, and intelligent writing

The CIA's Family Jewels (2007)

Societal Impacts: Claude's values across models and languages

Cyber Resilience Act

Anthropic's state-by-state plan to ratchet up AI rules

Show HN: PromptMan: A native macOS app for saving and reusing AI prompts

Never procrastinate again. Stick to TaskLoco super smart sticky notes

FOSDEM 2026: Multi-relay msging & cryptographic identities w/ DeltaChat/Chatmail

ChatGPT Subagents 2

Show HN: AI-CLI – tiny C terminal assistant powered by local LLM