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?

The top,771 sites block at least one AI search crawler

Prototype graph-based social media

O'Charley's

Apple, Please Open Up iOS

Show HN: Xivizley – Visual Docker Compose and Homelab Architect

Reaction: "A Quick Look at Atomics in C"

Show HN: Liniora – Ever thought about replacing your project manager?

"The CUDA Moat is Gone" – TechTechPotato with AI& founder David Bennet [video]

Experiment: How easy is it to buy a research paper on the black market?

OpenRGB 1.0 Released

Show HN: Rust-split – save your tokens on large Rust source files

Build with Replit Against Managed Postgres in Databricks Apps

Journal Editors: How are you evaluating AI assisted papers?

We're All Going to Die

Karaoke for one: China's $1T 'loneliness economy'

Overshoot: The World Is Hitting Point of No Return on Climate

Hydra

Show HN: Parallel Coding Agents on Mobile

Show HN: Email Client with Backups

AI changing the calculus for Canadian students interested in comp sci

Fresh: Terminal based IDE and text editor: easy, powerful and fast

TinyEMU is a system emulator for the RISC-V and x86 archs

ProLogium begins mass production of solid-state battery at 381 Wh/kg

HTTPS Everywhere?

Subjective reports and visual targets during attempted out-of-body experiences

Here Comes the Sun

Show HN: TattooPreview AI – a planning workflow for tattoo artist conversations

Show HN: I wrote a book on using AI in game design production (free on GitHub)

Fuck it, make it anyway

Dimit – warm a Mac screen to pure red and pin the backlight against PWM