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?

I tracked down the thief who stole $200k of Lego [video]

Limerick

We Were Wrong About Fasting Study Finds

C Constructs That Still Don't Work in C++ – and a Few That Changed

A Data Mining Adventure into the World of Lichess Puzzle Database

The Verification Problem (On OpenAI's Erdős Disproof)

AI Can Do Anything

Does bulk memmove speed up std:remove_if? (No.)

European Data Centers Reuse Waste Heat to Heat Homes

How to Call an API from an Email

"Long-Term Support" doesn't mean what you think

2of3: Enter a secret. Get 3 cards

SpaceX, OpenAI and Anthropic IPOs set to test limits of AI boom

Dark trades' risk destroying London's stock markets

BNoise – The Easiest Music Maker

Hacker Typer – Hacker Screen

Reddit stock drops almost 6%, Meta launches standalone app for online forums

Cleaning Station

The phrase "taste is the differentiator" is not beneficial

Fauxx – Data poisoning for your everyday tracking

Amazon Web Services – Four Years and Out

What does grep stand for, and the 75 year history of the regular expression

Commodity Intelligence

British power prices are increasingly independent from gas

Show HN: Qavvali Wiki

Show HN: Panorama – Review Code, Faster

The C++ Standard Library Has Been Walking Itself Back for Fifteen Years

Their Phones Were Stolen in London. Then the Threats Started

Easier bets to get early customer validation and VC attention

Pre-ASI Society