aho-corasick
tldr
aho-corasick | tldr | |
---|---|---|
21 | 262 | |
950 | 48,494 | |
- | 0.8% | |
7.2 | 10.0 | |
about 1 month ago | about 10 hours ago | |
Rust | Markdown | |
The Unlicense | GNU General Public License v3.0 or later |
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aho-corasick
- Aho-Corasick Algorithm
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Identifying Rust's collect:<Vec<_>>() memory leak footgun
You can't build the contiguous variant directly from a sequence of patterns. You need some kind of intermediate data structure to incrementally build a trie in memory. The contiguous NFA needs to know the complete picture of each state in order to compress it into memory. It makes decisions like, "if the number of transitions of this state is less than N, then use this representation" or "use the most significant N bits of the state pointer to indicate its representation." It is difficult to do this in an online fashion, and likely impossible to do without some sort of compromise. For example, you don't know how many transitions each state has until you've completed construction of the trie. But how do you build the trie if the state representation needs to know the number of transitions?
Note that the conversion from a non-contiguous NFA to a contiguous NFA is, relatively speaking, pretty cheap. The only real reason to not use a contiguous NFA is that it can't represent as many patterns as a non-contiguous NFA. (Because of the compression tricks it uses.)
The interesting bits start here: https://github.com/BurntSushi/aho-corasick/blob/f227162f7c56...
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Ask HN: What's the fastest programming language with a large standard library?
Right. I pointed it out because it isn't just about having portable SIMD that makes SIMD optimizations possible. Therefore, the lack of one in Rust doesn't have much explanatory power for why Rust's standard library doesn't contain SIMD. (It does have some.) It's good enough for things like memchr (well, kinda, NEON doesn't have `movemask`[1,2]), but not for things like Teddy that do multi-substring search. When you do want to write SIMD across platforms, it's not too hard to define your own bespoke portable API[3].
I'm basically just pointing out that a portable API is somewhat oversold, because it's not uncommon to need to abandon it, especially for string related ops that make creative use of ISA extensions. And additionally, that Rust unfortunately has other reasons for why std doesn't make as much use of SIMD as it probably should (the core/alloc/std split).
[1]: https://github.com/BurntSushi/memchr/blob/c6b885b870b6f1b9bf...
[2]: https://github.com/BurntSushi/memchr/blob/c6b885b870b6f1b9bf...
[3]: https://github.com/BurntSushi/aho-corasick/blob/f227162f7c56...
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Ripgrep is faster than {grep, ag, Git grep, ucg, pt, sift}
Oh I see. Yes, that's what is commonly used in academic publications. But I've yet to see it used in the wild.
I mentioned exactly that paper (I believe) in my write-up on Teddy: https://github.com/BurntSushi/aho-corasick/tree/master/src/p...
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how to get the index of substring in source string, support unicode in rust.
The byte offset (or equivalently in this case, the UTF-8 code unit offset) is almost certainly what you want. See: https://github.com/BurntSushi/aho-corasick/issues/72
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Aho Corasick Algorithm For Efficient String Matching (Python & Golang Code Examples)
This is an implementation of the algorithm in Rust as well if someone is curious. Though this code is written for production and not teaching.
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When counting lines in Ruby randomly failed our deployments
A similar fix for the aho-corasick Rust crate was made in response
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Aho-corasick (and the regex crate) now uses SIMD on aarch64
Teddy is a SIMD accelerated multiple substring matching algorithm. There's a nice description of Teddy here: https://github.com/BurntSushi/aho-corasick/tree/f9d633f970bb...
It's used in the aho-corasick and regex crates. It now supports SIMD acceleration on aarch64 (including Apple's M1 and M2). There are some nice benchmarks included in the PR demonstrating 2-10x speedups for some searches!
- Stringzilla: Fastest string sort, search, split, and shuffle using SIMD
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ripgrep is faster than {grep, ag, git grep, ucg, pt, sift}
Even putting aside all of that, it might be really hard to add some of the improvements ripgrep has to their engine. The single substring search is probably the lowest hanging fruit, because you can probably isolate that code path pretty well. The multi-substring search is next, but the algorithm is very complicated and not formally described anywhere. The best description of it, Teddy, is probably my own. (I did not invent it.)
tldr
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Ask HN: Is there a GUI for bash shell?
Maybe this already helps: https://github.com/tldr-pages/tldr
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Try / Ripgrep in Y Minutes
A bit of an aside, but I really like "guides to things we otherwise take for granted". So few man pages are built around example use cases, but those are often what make the case for a tool!
A similar spirit to projects like https://github.com/tldr-pages/tldr/ , but this has a lot more useful detail.
The ripgrep author has a blog post on performance and benchmarking that is an interesting read in itself: https://blog.burntsushi.net/ripgrep/
- Serving my blog posts as Linux manual pages
- Tldr: Simplified and community-driven man pages
- Tell HN: My Favorite Tools
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Should you add screenshots to documentation?
Looks like bro pages is archived and they recommend https://github.com/tldr-pages/tldr or https://github.com/cheat/cheat
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Have i made my own linux distro? ^_^
a very excellent tool to grab is TLDR https://tldr.sh/
- fixedIt
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Day 2 - Basic navigation
And that's why tldr is such a powerful tool! You can easily install it with sudo apt install tldr or follow this demo.
- Tldr Pages
What are some alternatives?
uwu - fastest text uwuifier in the west
cheat - cheat allows you to create and view interactive cheatsheets on the command-line. It was designed to help remind *nix system administrators of options for commands that they use frequently, but not frequently enough to remember.
ripgrep - ripgrep recursively searches directories for a regex pattern while respecting your gitignore
tealdeer - A very fast implementation of tldr in Rust.
perf-book - The Rust Performance Book
cheat.sh - the only cheat sheet you need
fzf - :cherry_blossom: A command-line fuzzy finder
zsh-autosuggestions - Fish-like autosuggestions for zsh
bat - A cat(1) clone with wings.
navi - An interactive cheatsheet tool for the command-line
fd - A simple, fast and user-friendly alternative to 'find'
fish-shell - The user-friendly command line shell.