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?

Road Trains Roam the Backroads of Australia

OpenAI Models Joined Forces Months Ahead of Hugging Face Hack

What AI First Engineering Orgs Look Like

Federal appeals court OKs Florida anti-drag show law

A New Kind of Bearing [video]

Google Genie 3: Interactive worlds generated by AI

France is banning unsolicited telemarketing calls starting next week

Biggest US law firms explore selling stakes to private equity

Employers are hiring less but paying more

ConvoKit: Conversational Analysis Toolkit

'Sell America' Debate Re-Emerges as US Policies Sow Doubts

They Write the Right Stuff – (1996)[pdf]

Open Micro-Manipulator

You don't need to be a developer to build a real software today

Voice Commanding the PRETTY Spacecraft over Amateur Radio (To Play Doom)

Stripe Lands in Minecraft

WYSIWYG Markdown Editor: Paste webpages, spreadsheets and images directly

The Monty Hall Problem

Why Do We Tolerate Elon Musk's Racist Commentary?

DeepSeek announced to raise its API price tremendously

The Zillion Encodings of NOP [video]

Two simple tests to see how your fitness compares with Elite older athletes

Teamsters sue California over self-driving truck rules

Two sizes fit most: Postgres and ClickHouse

Touring the Consensus, Six Months In

How to Build an LLM-Powered Database Query Bot for Your Web App in 1 Day

Smalltalk Report from 1991 to 1996

Ask HN: Which model is best for pair-programming?

Caesars Entertainment – Responsible Gaming Exclusion

Half of vaccines are binned – 'fridge-free' versions could change that