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?

How you could have invented muon from memory

Finding Panics with Call Graph Analyzer

The hydrogen atom barely exists on Earth – now we've made it in a flask

Mats Kindahl: Building a Table Access Method, Part 6: Truncate

Hyperbolic – Open-Access GPU and AI Cloud

Demoted, Still Liable

How to Deal with the Client Pyramid

How to Pitch Damn Well

Self-Hosted Orbs

Breaking changes in third-party APIs are turning into a full-time job

No JavaScript Needed

Decompiling Games with AI: Virtueel Zoetermeer

Kentucky man becomes the first humanist granted religious exemption from AI

Show HN: QuickRef – client-side developer tools

What the Count Misses

Obsessed with the Outcome

Legora is building the agentic operating system for legal work

The Doorman Fallacy

Show HN: iPhone app for SMS into split expenses – 100 % on-device, no account

Transmission voie-machine (Railway safety technology)

Artificial Analysis v5 and the benchmarker's dilemma

Search golden sets are anything but

Show HN: Harness Corp – An incremental game powered by a local LLM using WebGPU

No One Needs Us Anymore [video]

Show HN: QuireKit – Real page layout for rich-text editing in the browser (MIT)

Gemini API CLI

Sunlight at night: US startup's demonstration of lighting Earth from space

Leymosun 0.4.45 Update: Leymosun Science: Quantum Research Toolkit

Conversational Interfaces: Where Are We Today? Where Are We Heading? (2016)

More Is Less