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?

AI usage generates a fragile codebase

The command you checked wasn't the command that ran

AI and Irontown

Ask HN: How has AI changed your project estimates and team composition?

Datacenter Systems Spending to Go Through the Roof in 2027

What's New in Node.js 27

Research Finds Outright Grants of Cash Are Effective Form of Aid to the Poor

Mood Clip Social Website

Jane Street: Socratic Tutor

Trump says FBI investigating Nvidia boss's affair with alleged Chinese spy

Loose Thoughts on the Future of Abstractions

Outlook bounces legit emails, Microsoft's authentication crackdown goes sideways

Embracing or rejecting short-termism (or both?)

The Afterlife of the Berlin Wall

cybershe\f: open-source digital bookshelves and async book clubs

Best Charcoal Chicken in Abu Dhabi – Shams Al Bahar

Alt-Erlaa, Vienna: 'The World's Best Council Housing?'

Ethereum Foundation sued after firing employee over mandatory suicide pact

Deskland – Adaptive Windows Wallpaper Around Your Icons

The Bad Grade That Changed the U.S. Constitution

Google TPU 8tx Pairs AMD EPYC Turin Hosts with Confidential Computing

Show HN: A fan-made GTA 6 radio wheel with 12 playable stations

A faster Easter date function

Microsoft teaches schools that free email was just a phase

Tinysub: iTunes like web player for subsonic servers

Pivector Labs – A microscope that records atoms at video rates

Russia's combat losses in the data of Rosstat

Hi

NTSB investigators have recovered the Learjet 60's cockpit voice recorder (CVR)

Tell HN: Gemini Carbon released