simdutf
eve
simdutf | eve | |
---|---|---|
11 | 6 | |
960 | 848 | |
4.8% | - | |
9.1 | 8.9 | |
3 days ago | 6 days ago | |
C++ | C++ | |
Apache License 2.0 | Boost Software License 1.0 |
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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
eve
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Lack of modern scientific libraries written in C
C++ offers tools for writing better APIs, and since the addition of concepts in C++20 it offers much better API enforcement. Writing an equivalent to libraries such as {fmt} or EVE is not possible in anything we’d call C.
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Library that could generate vectorized code for different instruction sets?
Here is a doc on how we suggest to do it: https://jfalcou.github.io/eve/multiarch.html Here is complete code of that example: https://github.com/jfalcou/eve/tree/main/examples/multi-arch
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SIMD intrinsics and the possibility of a standard library solution
My source for this was the statement:
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C++'s smaller cleaner language
Indeed you cannot. Then again, you couldn't write a library like fmtlib in C in the first place. I mean why do you complain about C++ features which enable you to write libraries you otherwise couldn't? How would you expect to implement equivalent libraries to EVE or mp-units in C alone?
What are some alternatives?
simdutf8 - SIMD-accelerated UTF-8 validation for Rust.
highway - Performance-portable, length-agnostic SIMD with runtime dispatch
DirectXMath - DirectXMath is an all inline SIMD C++ linear algebra library for use in games and graphics apps
aoc2021
simde - Implementations of SIMD instruction sets for systems which don't natively support them.
ispc - Intel® Implicit SPMD Program Compiler
Vc - SIMD Vector Classes for C++
dmd - dmd D Programming Language compiler
simdjson - Parsing gigabytes of JSON per second : used by Facebook/Meta Velox, the Node.js runtime, ClickHouse, WatermelonDB, Apache Doris, Milvus, StarRocks
fractals - Mandelbrot renderer with SIMD (NEON/AVX) acceleration.
colrcv - C Library for converting Colours between different Colour Models
pacman - A proof that Idris is pacman complete