aho-corasick
rust-semverver
aho-corasick | rust-semverver | |
---|---|---|
21 | 8 | |
950 | 641 | |
- | - | |
7.2 | 1.7 | |
about 1 month ago | 10 months ago | |
Rust | Rust | |
The Unlicense | BSD 3-clause "New" or "Revised" License |
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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.)
rust-semverver
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A byte string library for Rust
1) No. I think semver is just fine for its intended purpose. I mean, I'm sure its spec could be improved in various ways, but its fundamental idea seems fine to me. I think it's just important to remember that semver is a means to an end, and not an end itself. It is a tool of communication most useful in a decentralized context.
2) No.
3) See: https://github.com/rust-lang/rust-semverver --- But also, this is only ever going to be a "best effort" sort of thing. Semver isn't just about method additions or deletions, but also behavior.
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Toward fearless `cargo update`
How does this compare to cargo-semverver?
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Are crate versions numbers all low because Rust just works?
Found this: https://github.com/rust-lang/rust-semverver but it doesn't seem to act on git log/diffs... just FYI.
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Implied bounds and perfect derive
Enter rust-semverver!
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my company refuses to use rust because it changes to much
Rust type system on the other hand does not allow this. Traits are monotonic logic: adding trait-impls / most qualifiers does't influence already existing and compiling code (note: for code that doesn't rely on disambiguation to compile). There's rules that clarify this disambiguations and breaking/non-breaking changes according to the type system. There's SemVerVer to automatically verify those guidelines.
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Would you want crates.io/cargo publish to enforce strictly correct SemVer conventions?
In my case it wasn't so bad and an easy fix was fast to write, but it got me thinking of how much of a problem this is for the wider ecosystem. Some searching showed me, that of course there is a tool rust-semverver to do exactly that. Sadly it errors on my system (or maybe im just using it wrong). Would've been interesting to see how often this actually happens on crates.io and how much of a problem this really is.
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Semantic Versioning Will Not Save You
There's been an attempt at this for the Rust ecosystem: https://stackoverflow.com/questions/41185023/what-exactly-is...
There's also a library that attempts to automatically check sermver adherence of a crate: https://github.com/rust-lang/rust-semverver
And there has been quite a bit of effort into preventing semver requirements from fracturing the ecosystem. This revolves around the compiler working with multiple major versions of a single library: https://github.com/dtolnay/semver-trick
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cargo-incversion, a command line utility to update Cargo.toml version
Turns out it already exists: https://github.com/rust-lang/rust-semverver
What are some alternatives?
uwu - fastest text uwuifier in the west
wg - Coordination repository of the embedded devices Working Group
ripgrep - ripgrep recursively searches directories for a regex pattern while respecting your gitignore
cargo-semver-checks-action - A GitHub Action for running cargo-semver-checks
perf-book - The Rust Performance Book
cargo-semver-checks - Scan your Rust crate for semver violations.
fzf - :cherry_blossom: A command-line fuzzy finder
blog - My blog.
bat - A cat(1) clone with wings.
imgref-iter - A small crate for iterating over the rows or columns of `imgref` buffers
fd - A simple, fast and user-friendly alternative to 'find'
really-small-backpack-example - A really small example of the Backpack module system for Haskell