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?

Spire: Structure-Preserving Interpretable Retrieval of Evidence

I took a physics class as a software engineer

Munich's IT transition: open-source is the default for the new coalition

Great Essays About Biology

Viral Marketing

Medicare's new payment model is built for AI. Most of the tech world has no idea

More concentrated precipitation decreases terrestrial water storage

Lobotomized Claude Code: system-prompt overrides for Opus 4.7

Hondurasgate.ch Portal Under Attack

Token Dashboard – local desktop app to see where your Claude Code tokens go

Show HN: Building effective Human-AI hybrid decision-making ecosystem

Windows 11 PCs Compared to MacBook Neo

An 'Impossible' Idea Led to a Pancreatic Cancer Breakthrough

San Fransokyo: imagining a denser San Francisco

LLMs are breaking 20 year old system design

ContextPilot... I got tired of paying for the same system prompt 200 times

The Per-Minute Calling Myth: The Hidden Economics of Voice and Video Calling API

"Call A Republican" San Francisco public phone lets you call a Texas Republican

Pythons new httpx fork: httpx2

TSMC unveils process technology roadmap through 2029 – A12, A13, N2U announced

Pullback Drive

Fragnesia (Linux LPE)

Cisco to Cut Jobs in Shift to Capture More AI Demand

PyTorch 2.12 Released

Show HN: Sinain captures screen and audio in KG, shares it with agents/peers

QWEN2.5-1.5B Abliterated Release for Android Mobile

I tested GPT-5.5, Claude Opus 4.7, and Gemini 3.1 Pro on financial-control

I was asked to install malware during a fake interview

TinyStories-260K running locally on a stock Game Boy Color

Content-defined chunking added to Bazel