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?

Sperm whale communication clicks can travel up to 70 km

Data Warehouse Isn't Integrated Just Because the Tables Are in One Place

Everything You Do Is Being Recorded

Silencing brain's prefrontal cortex boost creative problem-solving in mice

Show HN: Inspect any MCP server – latency, token usage, and security scans

Switching to electric stoves can dramatically cut indoor air pollution

Real Engineers Dig with Their Bare Hands

A quick look at zero-knowledge proofs

Show HN: Pier – Give every agent session its own cloud VM, on your own infra

Hybrid Structured Editing

Myspace eyes comeback as an an 'antidote' to social media fatigue

The Analytic Monopoly on AI Philosophy

Story of Roomy with Handmade Illustrations

India's Republic of Uncles

If You Get in a Car Crash, the Risk Is Growing Your Insurance Won't Pay

Tcl Note A1 Nxtpaper Review (2026): A Hybrid Tablet for Taking Notes and Watchi

One Japanese village defied the tsunami (2011)

We are witnessing the death of the games console

The Aaronson Oracle: an interactive lesson in human predictability

Ask HN: Should AI's tell you they're AI?

Show HN: Argonix – One AI-powered platform for SRE and cloud operations

Show HN: Free QR Code Generator – URL, Text, WiFi and VCard – Free, No Signup

Angel Investor Simulator

Ask HN: What you using local models for?

Solitude as a new aspirational lifestyle: 'We are not lonely'

Softlanding Linux System – ArchiveOS

The economics professor who keeps running office hours

Show HN: Restoredrill proves your Postgres backups restore

Taco Bell fans won't let cyclospora come between them and food

Reducing Hallucinations in LLM-Gen. Code via Semantic Triangulation (OOPSLA 26)