Packed Data Support in Haskell

https://arthi-chaud.github.io/posts/packed/

77•matt_d•10mo ago

Comments

nine_k•10mo 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•10mo ago

We are always reinventing wheels. If we didn't, they'd all still be made of wood.

Zolomon•10mo ago

They mention this in the article.

spockz•10mo ago

It reminds me more of flat buffers though. Does protobuf also have zero allocation (beyond initial ingestion) and no pointer jumps?

cstrahan•10mo ago

No, one example of why being variable sized integers.

See https://protobuf.dev/programming-guides/encoding/

carterschonwald•10mo ago

One thing that sometimes gets tricky in these things is handling Sub term sharing. I wonder how they implemented it.

tlb•10mo 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•10mo 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•10mo 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•10mo ago

honestly i wish more stuff worked this way - fewer hops in memory always makes me happy

lordleft•10mo ago

This was very well written. Excellent article!

NetOpWibby•10mo ago

Is this like MessagePack for Haskell?

Journeying through Optimization with Heuristics [video]

Cookie Jars Capture American Kitsch (2023)

Why LLMs Are Not (Yet) the Silver Bullet for Unstructured Data Processing

Pyodide: a Python distribution based on WebAssembly

Ask HN: How do you promote a new platform and reach critical mass?

CorridorKey: Perfect Green Screen Keys

ECJ says EU states must change gender of citizens even if nat'l laws forbid it

Dark money group pays influencers $1.5K for posts attacking Democratic candidate

TweetStyler – Stylish Unicode fonts for social media (especially X)

War, AI, the Oscars and SXSW?

The Shape of the Thing

Iran unleashes oil shock to blunt US firepower

Why the militaries are scrambling to create their own Starlink

APL9: An APL for Plan 9

Show HN: My personal AI-powered dev workstation

Dex: Task Tracking for Agents

Claude overtaking ChatGPT in the enterprise – measured by job posts mentions

Show HN: AI milestone verification for construction using AWS

JEP Draft: Enhanced Local Variable Declarations

Multi-dimensional weighted random roll (choice, dice, selection)

Show HN: Diraigent – Self-hosted orchestration for AI coding agents

If Claude Code is performing poorly, you might be in an A/B test

Ukraine's Flamingo Cruise Missile Will Reshape the War's Dynamics

Alpine glacier holds history dating back to the Romans. And it's melting–fast

China's ByteDance Gets Access to Top Nvidia AI Chips

An AI that plans multi-city trips in seconds. CRAZY product

Public Memories – Comedy Skits from Krazam [video]

1M context is now generally available for Opus 4.6 and Sonnet 4.6

Show HN: I Made a PS1 Static Recompiler with No Prior Experience (and Claude)

Yes, and