aho-corasick
miri
aho-corasick | miri | |
---|---|---|
21 | 122 | |
950 | 3,973 | |
- | 2.3% | |
7.2 | 10.0 | |
about 1 month ago | about 6 hours ago | |
Rust | Rust | |
The Unlicense | Apache License 2.0 |
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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.)
miri
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Rust: Box Is a Unique Type
>While we are many missing language features away from this being the case, the noalias case is also magic descended upon box itself, with no user code ever having access to it.
I'm not sure why the author thinks there's magic behind Box. Box is not a special case of `noalias`. Run this snippet with miri and you'll see the same issue: https://play.rust-lang.org/?version=stable&mode=debug&editio...
`Box` _does_ have an expectation that its inner pointer is not aliased to another Box (even if used for readonly operations). See: https://github.com/rust-lang/miri/issues/1800#issuecomment-8...)
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Bytecode VMs in Surprising Places
Miri [0] is an interpreter for the mid-level intermediate representation (MIR) generated by the Rust compiler. MIR is input for more processing steps of the compiler. However miri also runs MIR directly. This means miri is a VM. Of course it's not a bytecode VM, because MIR is not a bytecode AFAIK. I still think that miri is a interesting example.
And why does miri exist?
It is a lot slower. However it can check for some undefined behavior.
[0]: https://github.com/rust-lang/miri
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RFC: Rust Has Provenance
Provenance is a dynamic property of pointer values. The actual underlying rules that a program must follow, even when using raw pointers and `unsafe`, are written in terms of provenance. Miri (https://github.com/rust-lang/miri) represents provenance as an actual value stored alongside each pointer's address, so it can check for violations of these rules.
Lifetimes are a static approximation of provenance. They are erased after being validated by the borrow checker, and do not exist in Miri or have any impact on what transformations the optimizer may perform. In other words, the provenance rules allow a superset of what the borrow checker allows.
- Mir: Strongly typed IR to implement fast and lightweight interpreters and JITs
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Running rustc in a browser
There has been discussion of doing this with MIRI, which would be easier than all of rustc.
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Piecemeal dropping of struct members causes UB? (Miri)
This issue has been fixed: https://github.com/rust-lang/miri/issues/2964
- Erroneous UB Error with Miri?
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I've incidentally created one of the fastest bounded MPSC queue
Actually, I've done more advanced tests with MIRI (see https://github.com/rust-lang/miri/issues/2920 for example) which allowed me to fix some issues. I've also made the code compatible with loom, but I didn't found the time yet to write and execute loom tests. That's on the TODO-list, and I need to track it with an issue too.
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Interested in "secure programming languages", both theory and practice but mostly practice, where do I start?
He is one of the big brains behind Miri, which is a interpreter that runs on the MIR (compiler representation between human code and asm/machine code) and detects undefined behavior. Super useful tool for language safety, pretty interesting on its own.
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Formal verification for unsafe code?
I would also run your tests in Miri (https://github.com/rust-lang/miri) to try to cover more bases.
What are some alternatives?
uwu - fastest text uwuifier in the west
cons-list - Singly-linked list implementation in Rust
ripgrep - ripgrep recursively searches directories for a regex pattern while respecting your gitignore
sanitizers - AddressSanitizer, ThreadSanitizer, MemorySanitizer
perf-book - The Rust Performance Book
rust - Empowering everyone to build reliable and efficient software.
fzf - :cherry_blossom: A command-line fuzzy finder
Rust-Full-Stack - Rust projects here are easy to use. There are blog posts for them also.
bat - A cat(1) clone with wings.
rfcs - RFCs for changes to Rust
fd - A simple, fast and user-friendly alternative to 'find'
nomicon - The Dark Arts of Advanced and Unsafe Rust Programming