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?

No More Drugstore Head Shots: Passport Applications Go Digital

AI Agents tasked with making money commit fraud on the inernet

Tobi Lütke on AI agents at Shopify and the future of work [video]

Goldman Sachs to Launch Voting Instruction Program

Ask HN: Realistic approach to making roon[0] more compact/portable?

100 Objects #11: Brannock Device

Rust to WGSL transpiler `wgsl-rs` released

Meta admits Muse's likeness to OpenClaw isn't a coincidence

Google announces Gemini 4, restricts access to 'trusted cyber defenders'

Gemini 4 Argon: Google is back among the top three labs in intelligence achieved

Latte Art for Nerds

The Great Cholesterol Scam and the Dangers of Statins

Nobody Is Listening on Port 8125

SynthID Bio: Watermarking methods for synthetic biology

Refract – A Quest Emulation Tool

Agent-db-scan – See what a Postgres login can do

Ask HN: What Are You Building?

Millions of dollars paid to AI providers, where was that money going before?

The Bay Area may be hottest wealth market. Banks are racing to cash in

Where Did the Productivity Gains Go?

ChimpBench – Chimpanzee Population Simulator

Is it safe to charge your phone overnight?

192GB Framework Desktop open for pre-order

Coding Agents Are Broken

FOSS Alternative to Nextcloud

Show HN: Desbordante 2.5.0 Released

The Linguistics Iceberg Explained [video]

Man Killed After Bag Gets Stuck in Subway Doors, Police Say

RexaDB: Modern Database Studio

Check a cold-chain shipment from its logger CSVs and get a signed, offline-verif