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?

The Rulers of the World Have Ticker Symbols

Hoard – A game save sync and backup where 10 save of a 2 GB size cost 2 GB

Show HN: A fullscreen Game of Life in which every board is a runnable program

ZUMA Press

Show HN: Sibuna an open source web application firewall with proof of work

The engineering habits that gave Dirac an edge as a physicist

Lobbying Is Corruption

Replacing pyinstaller with 100 lines of code

Being mean to Claude could get you banned as Anthropic introduces new rules

Orangutan mothers seek out playmates for young

2025-10-10 front – Hacker News

No One Lives Forever decompiled source code

Python 3.15

Why Drug Trafficking Is Now Almost a Human Right in Canada

Why Alberta farmers are suddenly demanding tractors they can fix themselves

Claude Code and Codex break on different MCP features

5-MeO-DMT sometimes cancels the Ebbinghaus illusion

Westermarck Effect

Enrico Fermi's 125th birthday: Bring Fermi Poker to your school or university

PVX-001: open-source Covid-19 vaccine starts Phase 1 trial

Synthetic corporate dataset – 1M and 10M emails and calendar events

Voice Dictation for Linux that learns as you speak

Dialer applications can be exploited to achieve 1-click MMI execution in Android

MailCheap: Self-hosted newsletters on Amazon SES. About $0.10 per 1k emails

Tom Brown used GOP ties to broker a $1.25B/month SpaceX compute deal

The Missing Piece in Rust Error Handling

Enzo's – AI home search that shows cap rate and flags overpriced homes

Is Anthropic a Good Business?

FDA may allow some toxic chemicals to be added to food without safety review

I tested whether AI agents obey text you never see. 4 of 8 did, every time