tree-flat
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tree-flat | us | |
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2 | 2 | |
25 | 55 | |
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1.9 | 1.5 | |
about 1 year ago | 4 months ago | |
Rust | Go | |
Apache License 2.0 | MIT License |
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tree-flat
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Ask HN: What are some 'cool' but obscure data structures you know about?
I made https://github.com/mamcx/tree-flat as flattened stored tree in pre-order that allows for very fast iterations even for childs/parent queries. Is based on APL, so not that novel.
I also like a lot the relational model, is not that much represented so I making a language on top of it: https://tablam.org.
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What’s everyone working on this week (9/2022)?
Working in the flattest tree library for Rust (https://github.com/mamcx/tree-flat), inspired by the talk “High-performance Tree Wrangling, the APL Way” by Aaron Hsu.
us
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Ask HN: What are some 'cool' but obscure data structures you know about?
It might be easier to think about it as a stack, rather than a tree. Each element of the stack represents a subtree -- a perfect binary tree. If you ever have two subtrees of height k, you merge them together into one subtree of height k+1. Your stack might already have another subtree of height k+1; if so, you repeat the process, until there's at most one subtree of each height.
This process is isomorphic to binary addition. Worked example: let's start with a single leaf, i.e. a subtree of height 0. Then we "add" another leaf; since we now have a pair of two equally-sized leaves, we merge them into one subtree of height 1. Then we add a third leaf; now this one doesn't have a sibling to merge with, so we just keep it. Now our "stack" contains two subtrees: one of height 1, and one of height 0.
Now the isomorphism: we start with the binary integer 1, i.e. a single bit at index 0. We add another 1 to it, and the 1s "merge" into a single 1 bit at index 1. Then we add another 1, resulting in two 1 bits at different indices: 11. If we add one more bit, we'll get 100; likewise, if we add another leaf to our BNT, we'll get a single subtree of height 2. Thus, the binary representation of the number of leaves "encodes" the structure of the BNT.
This isomorphism allows you to do some neat tricks, like calculating the size of a Merkle proof in 3 asm instructions. There's some code here if that helps: https://github.com/lukechampine/us/blob/master/merkle/stack....
You could also check out section 5.1 of the BLAKE3 paper: https://github.com/BLAKE3-team/BLAKE3-specs/blob/master/blak...
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My proposal to the Foundation: add first-class S3 provider support
This isn't what I'm asking for - I don't care if it's baked into us, exists as a backend for minio, uses PseudoKV https://github.com/lukechampine/us/issues/67, or whatever the case may be. I see no value in sending any third party my private data in an unencrypted form (uploading to your server, even if over HTTPS, you got my data).
What are some alternatives?
multiversion-concurrency-control - Implementation of multiversion concurrency control, Raft, Left Right concurrency Hashmaps and a multi consumer multi producer Ringbuffer, concurrent and parallel load-balanced loops, parallel actors implementation in Main.java, Actor2.java and a parallel interpreter
swift - the multiparty transport protocol (aka "TCP with swarming" or "BitTorrent at the transport layer")
atomic-server - An open source headless CMS / real-time database. Powerful table editor, full-text search, and SDKs for JS / React / Svelte.
ego - EGraphs in OCaml
conserve - 🌲 Robust file backup tool in Rust
pvfmm - A parallel kernel-independent FMM library for particle and volume potentials
indicatif - A command line progress reporting library for Rust
lnd - Lightning Network Daemon ⚡️
TablaM - The practical relational programing language for data-oriented applications
ctrie-java - Java implementation of a concurrent trie
entt - Gaming meets modern C++ - a fast and reliable entity component system (ECS) and much more
hegg - Fast equality saturation in Haskell