simdutf
Better Enums
simdutf | Better Enums | |
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11 | 5 | |
960 | 1,593 | |
4.8% | - | |
9.1 | 3.7 | |
3 days ago | 3 months ago | |
C++ | C++ | |
Apache License 2.0 | BSD 2-clause "Simplified" License |
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simdutf
- Glibc Buffer Overflow in Iconv
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Vectorizing Unicode conversions on real RISC-V hardware
The project was mostly inspired by simdutf [0] which has been around for a couple of years already, and I don't think iconv has any of its vectorized implementations for other architectures.
[0] https://github.com/simdutf/simdutf
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Cray-1 performance vs. modern CPUs
I'm actually doing something quite similar in my, in progress, unicode conversion routines.
For utf8 validation there is a clever algorithm that uses three 4-bit look-ups to detect utf8 errors: https://github.com/simdutf/simdutf/blob/master/src/icelake/i...
Aside on LMUL, if you haven't encountered it yet: rvv allows you to group vector registers when configuring the vector configuration with vsetvl such that vector instruction operate on multiple vector registers at once. That is, with LMUL=1 you have v0,v1...v31. With LMUL=2 you effectively have v0,v2,...v30, where each vector register is twice as large. with LMUL=4 v0,v4,...v28, with LMUL=8 v0,v8,...v24.
In my code, I happen to read the data with LMUL=2. The trivial implementation would just call vrgather.vv with LMUL=2, but since we only need a lookup table with 128 bits, LMUL=1 would be enough to store the lookup table (V requires a minimum VLEN of 128 bits).
So instead I do six LMUL=1 vrgather.vv's instead of three LMUL=2 vrgather.vv's because there is no lane crossing required and this will run faster in hardware: (see [0] for a relevant mico benchmark)
# codegen for equivalent of that function
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What C++ library do you wish existed but hasn’t been created yet?
utf8 normalization, stemming, case insensitive comparison. https://github.com/unicode-rs example for rust What are options for C++? 1. translate to utf16 ( https://github.com/simdutf/simdutf ) and use icu -- slow 2. boost text, https://github.com/tzlaine/text , also slow (because the author doesn't care or couldn't care), we made a lot of patches to make our library faster than lucene, but still this part is slower than icu for utf16 (icu for utf16 also very slow...)
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[Preprint] Transcoding Unicode Characters with AVX-512 Instructions
You can find the corresponding assembly code in this repository. The main branch only contains implementations based on C++ with intrinsics.
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What's everyone working on this week (10/2023)?
The next big thing is making it LSP-compatible. All language servers must implement UTF-16 based character offsets, which is kinda unfortunate considering that files are much more likely to be stored in UTF-8 (I think?). I don't want to do the UTF-8 -> UTF-16 transcoding, so instead I'll use the excellent simdutf library to count how much code points a UTF-8 string would take if it was transcoded into UTF-16 — which is much faster than actual transcoding. So this is what I'm going to do this week — rewriting parsers to produce UTF-16 offsets + some final benchmarking. After that is done, I'll consider the "research" part of this project completed and will start writing an actual Markdown parser.
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Why would a language not natively support SIMD?
You can find the assembly code here: https://github.com/simdutf/simdutf/tree/clausecker The corresponding C++ code is in the main branch.
- High speed Unicode routines using SIMD
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text-2.0-rc1 with UTF8 underlying representation is available for testing!
Or via an ultrafast simdutf.
- Simdutf: Unicode validation and transcoding at billions of characters per second
Better Enums
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How to convert an enum to string in C++
I really like better_enums instead of magic_enums. There’s no limit on enum size with it: http://aantron.github.io/better-enums/
It was heavily used at a former employer of mine, so definitely a solid production-ready solution.
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What C++ library do you wish existed but hasn’t been created yet?
IIRC I then switched to another library doing the same stuff: https://github.com/aantron/better-enums It is not as magical, as it uses a special macro to define the enum, using dedicated syntax. So it only works for enums you yourself define. However, it did work a lot better for me with enums with huge values.
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Behind the magic of magic_enum
I can't keep up! First we have better enum, then some guy at a conference says we have to use wise enum instead, and now you speak of magic enum!
- What are some cool modern libraries you enjoy using?
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let's all be chads
If you need a laugh today, look at Better Enums library for C++. If you thought moving from C to C++ would let you leave macros behind, think again! Enums in C++ still suck (a bit less than in C though), so someone built a library to help with that. And it's built on macros. So you can only have 64 entries per enum. And the library's code is barely readable.
What are some alternatives?
simdutf8 - SIMD-accelerated UTF-8 validation for Rust.
C++ Format - A modern formatting library
DirectXMath - DirectXMath is an all inline SIMD C++ linear algebra library for use in games and graphics apps
stb - stb single-file public domain libraries for C/C++
simde - Implementations of SIMD instruction sets for systems which don't natively support them.
Klib - A standalone and lightweight C library
eve - Expressive Vector Engine - SIMD in C++ Goes Brrrr
American Fuzzy Lop - american fuzzy lop - a security-oriented fuzzer
Vc - SIMD Vector Classes for C++
Cppcheck - static analysis of C/C++ code
simdjson - Parsing gigabytes of JSON per second : used by Facebook/Meta Velox, the Node.js runtime, ClickHouse, WatermelonDB, Apache Doris, Milvus, StarRocks
constexpr-8cc - Compile-time C Compiler implemented as C++14 constant expressions