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?

AI agents now help attackers, including North Korea, manage their drudge work

Baochip-1x: A Mostly-Open, 22nm SoC for High Assurance Applications

Show HN: LocalRAG – Ask AI about your own documents (iOS/Android)

LangWatch: OpenTelemetry-Native LLM Observability Without the Vendor Lock-In

Bloom's Taxonomy

Claude Code, Claude Cowork and Codex #5

Why is GPT-5.4 obsessed with Goblins?

US FAA issues ground stop for all JetBlue planes

Amazon holds engineering meeting following AI-related outages

Government panel to compile groundwater report, includes users' nationalities

Show HN: I Was Here – Draw on street view, others can find your drawings

Prevent duplicate webhook executions in n8n (template)

United States Leads Dismantlement of One of the Largest Hacker Forums

Show HN: LLM Sycophancy Benchmark: Opposite-Narrator Contradictions

Windows: Microsoft broke the only thing that mattered

Language Birth

Show HN: Consul – AI Executive Assistant

Show HN: Mach9 Poker Beta

Battery Test [video]

Times New Roman drawn from memory (1 hour timelapse)

Build your OpenClaw superstack under a minute

Why the US Could Blame AI for Blowing Up the Iranian School

Do developers have agency? A study of 66k GitHub projects (7.3TB)

Appsflyer SDK Hijacked

Annotating for Agents

How curl Started [video]

Show HN: Claude Code Token Elo

Pwning NetBSD-Aarch64 (ARM)

Moment of Zen compilation from daily show

Htmx skill that includes everything