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?

State Engineering for Agents

CXL-ClusterSim: Modeling CXL-Based Disaggregated Memory

Dear Steve Lemay

Review of the MoErgo Glove80 Keyboard

Show HN: TIL – a timeline file format with a spiral viewer and editor

Show HN: Monolith, live typed queries on real Postgres for Java (no JDBC)

A Brief-Ish History of SETI. Part VIII: Paradox? What Paradox?

Go Hug an Open Source Maintainer (and Is Rsync Slop Now?)

Tell HN: Meta's AI support feature allows Instagram accounts to be stolen

Mapa.ua – Ukraine War Map

Can I just say f*** AI, f*** AI, f*** AI? [video]

Show HN: Font Wizard Pro – a font manager for iPhone and iPad

Simple systems are the best systems

Economic Growth and Community Well-Being Are Not Opposites

Beyond the API: Why Critical Infrastructure Is Going Streaming

Tiendli – e-commerce, reservations and marketplace for Latam SMEs

Spaniel – OpenTelemetry viewer for local development (Postman for your traces)

It's Not Just X. It's Y

Linear CEO Responds to Corgi (YC S24) CEO on Grindmaxxing

Atherton spent $145K to delay train electrification. The rest of us paid $400M

Fish Sleep a Lot Like Us. (They Even Nap.)

Ask HN: Do you use Cloudflare bot protection? If so, why do you use it?

Agent-stack – one command to make any repo token-efficient for Claude Code

G7 Agrees on Shared Language Around Open-Source AI, Open Weights AI

JavaScript Crossword

Show HN: Pictolab (online HDR image editor)

What Is Code

Pixelnet – The social network for game developers

The need for a socialist planned economy (2021)

New in Svelte – June 2026