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Top 23 C++ Simd Projects
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ncnn
ncnn is a high-performance neural network inference framework optimized for the mobile platform
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InfluxDB
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simdjson
Parsing gigabytes of JSON per second : used by Facebook/Meta Velox, the Node.js runtime, ClickHouse, WatermelonDB, Apache Doris, Milvus, StarRocks
Project mention: Make Ubuntu packages 90% faster by rebuilding them | news.ycombinator.com | 2025-03-18I think parsing once into a faster format (sqlite3 or parquet) would be more beneficial.
https://simdjson.org/
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As for math, that was the easiest choice as of yet. No doubt, GLM is a "gold standard" at this point. For OpenGL it is, at least. But, like with a lot of the other APIs, I decided to build a wrapper around it rather than directly reference the library in the engine's code. And for physics, well, I had not come upon that answer just yet. I did try to make my own physics logic at some point. And while it was, surprisingly, successful, I wanted more than just a simple physics layer. I wanted something more complex and, more importantly, faster than my implementation. I have not decided upon a physics library yet. But I'll cross that bridge when I come to it.
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I quite like highway.
As mentioned, last time I tried vqsort for RVV it was surprisingly slow.
I tried to replicate it yesterday, but noticed that vqsort is now disabled for RVV: https://github.com/google/highway/blob/400fbf20f2e40b984be12...
Does highway support sorting networks for non-128-bit vector registers?
When I tried to compile it for AVX512, the BaseCase seems to only use xmm registers: https://godbolt.org/z/qr9xoTGKn
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usearch
Fast Open-Source Search & Clustering engine × for Vectors & 🔜 Strings × in C++, C, Python, JavaScript, Rust, Java, Objective-C, Swift, C#, GoLang, and Wolfram 🔍
I wish I'd had a short answer :)
For years, I've had a hope to build it in the form of an open-core project: open-source SotA solutions for Storage, Compute, and AI Modeling built bottom up. You can imagine the financial & time burden of building something like that with all the weird optimizations and coding practices listed above.
A few years in, with millions spent out of my pocket, without any venture support or revenue, I've decided to change gears and focus on a few niche workloads until some of the Unum tools become industry standards for something. USearch was precisely that, a toy Vector Search engine that would still, hopefully, be 10x better than alternatives, in one way or another: <https://www.unum.cloud/blog/2023-11-07-scaling-vector-search...>.
Now, ScyllaDB (through Rust SDK) and YugaByte (through C++ SDK) are the most recent DBMSs to announce features built on USearch, joining the ranks of many other tech products leveraging some of those optimizations, and I was playing around with different open-source growth & governance ideas last year, looking for way to organize more collaborative environment among our upstream users, rather than competitive — no major releases, just occasional patches here and there.
It was an interesting period, but now I'm again deep in the "CUDA-GDB" land, and the next major release to come is precisely around Full-Text Search in StringZilla <https://github.com/ashvardanian/stringzilla>, and will be integrated into both USearch <https://github.com/unum-cloud/usearch> and somewhere else ;)
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xsimd
C++ wrappers for SIMD intrinsics and parallelized, optimized mathematical functions (SSE, AVX, AVX512, NEON, SVE))
Thanks, that's an important caveat!
> Meanwhile xsimd (https://github.com/xtensor-stack/xsimd) has the feature level as a template parameter on its vector objects
That's pretty cool because you can write function templates and instantiate different versions that you can select at runtime!
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Simd
C++ image processing and machine learning library with using of SIMD: SSE, AVX, AVX-512, AMX for x86/x64, NEON for ARM. (by ermig1979)
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proton
High-performance, low-footprint SQL database written in C++. Process millions of rows per second from Kafka/Pulsar, Iceberg, or ClickHouse, and seamlessly write results back. Supports powerful features like JOIN, CDC, UPSERT, and LOOKUP, enabling real-time analytics and ETL at scale. (by timeplus-io)
Project mention: Show HN: Open-Source C++ Apache Iceberg Client with Write Support | news.ycombinator.com | 2025-03-20 -
fast_float
Fast and exact implementation of the C++ from_chars functions for number types: 4x to 10x faster than strtod, part of GCC 12, Chromium, Redis and WebKit/Safari
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kfr
Fast, modern C++ DSP framework, FFT, Sample Rate Conversion, FIR/IIR/Biquad Filters (SSE, AVX, AVX-512, ARM NEON)
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DirectXMath
DirectXMath is an all inline SIMD C++ linear algebra library for use in games and graphics apps
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ada
WHATWG-compliant and fast URL parser written in modern C++, part of Node.js, Clickhouse, Redpanda, Kong, Telegram, Datadog and Cloudflare Workers.
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Project mention: Understanding SIMD: Infinite Complexity of Trivial Problems | news.ycombinator.com | 2024-11-30
I'm surprised no one has mentioned Vc. I found ispc clunky and not as performant, and std::simd didn't support some useful math ops like rsqrt. Vc has been around for years, I have no trouble including it in my codes, it has masking and many of the most useful math ops, and I can get over 1 TF/s on a consumer-grade Ryzen and at least 3 TF/s on the big Epyc CPUs.
https://github.com/VcDevel/Vc
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simdutf
Unicode routines (UTF8, UTF16, UTF32) and Base64: billions of characters per second using SSE2, AVX2, NEON, AVX-512, RISC-V Vector Extension, LoongArch64, POWER. Part of Node.js, WebKit/Safari, Ladybird, Chromium, Cloudflare Workers and Bun.
Lemire and collaborators often write in C++ intrinsics, or thin platform-specific wrappers on top of them.
I count ~8 different implementations [1], which demonstrates considerable commitment :) Personally, I prefer to write once with portable intrinsics.
https://github.com/simdutf/simdutf/tree/1d5b5cd2b60850954df5...
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Here is a bunch of simple examples: https://github.com/jfalcou/eve/blob/fb093a0553d25bb8114f1396...
I personally think we have the following strenghs:
* Algorithms. Writing SIMD loops is very hard. We give you a lot of ready to go loops. (find, search, remove, set_intersection to name a few).
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NOTE:
The open source projects on this list are ordered by number of github stars.
The number of mentions indicates repo mentiontions in the last 12 Months or
since we started tracking (Dec 2020).
C++ Simd discussion
C++ Simd related posts
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Three Fundamental Flaws of SIMD
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Show HN: Less Slow C++
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AWS Graviton 3 > Graviton 4 for Vector Similarity Search
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Realtime Math: C++11 alternative to glm and DirectX Math
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Purely Functional Sliding Window Aggregation Algorithm
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C Is Not Suited to SIMD
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Expressive Vector Engine – SIMD in C++
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A note from our sponsor - SaaSHub
www.saashub.com | 14 May 2025
Index
What are some of the best open-source Simd projects in C++? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | ncnn | 21,437 |
| 2 | simdjson | 20,284 |
| 3 | GLM | 9,884 |
| 4 | highway | 4,615 |
| 5 | usearch | 2,706 |
| 6 | ispc | 2,657 |
| 7 | ozz-animation | 2,571 |
| 8 | xsimd | 2,364 |
| 9 | Simd | 2,148 |
| 10 | proton | 1,788 |
| 11 | fast_float | 1,764 |
| 12 | kfr | 1,736 |
| 13 | DirectXMath | 1,643 |
| 14 | SatDump | 1,575 |
| 15 | ada | 1,532 |
| 16 | Vc | 1,483 |
| 17 | sse2neon | 1,378 |
| 18 | simdutf | 1,366 |
| 19 | libsimdpp | 1,273 |
| 20 | eve | 1,188 |
| 21 | FastNoise2 | 1,135 |
| 22 | hlslpp | 857 |
| 23 | Fastor | 779 |
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