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 Cone of Plausibility

Forte UI – React components whose palette derives from one CSS variable

Is Education for Industry or for Thinking?

Bigger Is Not Better

Show HN: Aethel-Core – Ultra-Lightweight Neuro-Symbolic WAF Built in SWI-Prolog

HN: Chef's Helper – Kitchen costing, prep, rotas and safety app

ShiftLens: Mech. Actuated Optical Surfaces for Switchable Appearances on 3D Objs

A simple tool to track projects, time, and income streams (£1.99)

Show HN: Alias – Custom Domain Email for Gmail

Bank ID vendor traced to a dark web license sale

In Defense of Polyfills

German startup sends first commercial rocket into space from Europe

MotionSites AI – Official Premium AI Website Prompts

Dither Garden

Ask HN: I just learned of the term "Recall@K" – tell me more please?

The aesthetic turn in intellectual property law copyright lessons from Pelham II

Ask HN: How safe are our password managers in face of LLM cyber attacks?

If a startup worth your career

Ask HN: Model Sycophancy Benchmarks?

Show HN: Ontoplano, FOSS Life Management desktop and mobile app with MCP server

The purpose of DNS is to spread scams

Show HN: Yume, a desktop workspace for Claude Code sessions

YouTube Had a Bug – I Used ChatGPT to Investigate

Casio 'CasioNaut' G-Shock GMC-2500 GAC-2500 Series: Price, Specs, Availability

Any Nix package, live in the browser

Tinymongo

GitHub Status – Disruption with Copilot Code Review

Where Will RISC-V Be in 20 Years? Poll Results

Show HN: Layerz – Native App Designer

Bitcoin mining data center condemned after leaking 3M gallons of water