highway

Efficient and performance-portable vector software Highway is a C++ library that provides portable SIMD/vector intrinsics. Documentation Previously licensed under Apache 2, now dual-licensed as Apache 2 / BSD-3. Why We are passionate about high-performance software. We see major untapped potential in CPUs (servers, mobile, desktops). Highway is for engineers who want to reliably and economically push the boundaries of what is possible in software. How CPUs provide SIMD/vector instructions that apply the same operation to multiple data items. This can reduce energy usage e.g. fivefold because fewer instructions are executed. We also often see 5-10x speedups. Highway makes SIMD/vector programming practical and workable according to these guiding principles: Does what you expect: Highway is a C++ library with carefully-chosen functions that map well to CPU instructions without extensive compiler transformations. The resulting code is more predictable and robust to code changes/compiler updates than autovectorization. Works on widely-used platforms: Highway supports seven architectures; the same application code can target various instruction sets, including those with 'scalable' vectors (size unknown at compile time). Highway only requires C++17 (language features, not necessarily the library) and supports four families of compilers. If you want to use Highway on other platforms, please raise an issue. Flexible to deploy: Applications using Highway can run on heterogeneous clouds or client devices, choosing the best available instruction set at runtime. Alternatively, developers may choose to target a single instruction set without any runtime overhead. In both cases, the application code is the same except for swapping HWY_STATIC_DISPATCH with HWY_DYNAMIC_DISPATCH plus one line of code. See also @kfjahnke's introduction to dispatching. Suitable for a variety of domains: Highway provides an extensive set of operations, used for image processing (floating-point), compression, video analysis, linear algebra, cryptography, sorting and random generation. We recognise that new use-cases may require additional ops and are happy to add them where it makes sense (e.g. no performance cliffs on some architectures). If you would like to discuss, please file an issue. Rewards data-parallel design: Highway provides tools such as Gather, MaskedLoad, and FixedTag to enable speedups for legacy data structures. However, the biggest gains are unlocked by designing algorithms and data structures for scalable vectors. Helpful techniques include batching, structure-of-array layouts, and aligned/padded allocations. We recommend these resources for getting started: SIMD programming with Highway talk SIMD for C++ Developers Algorithms for Modern Hardware Optimizing software in C++ Improving performance with SIMD intrinsics in three use cases Examples Online demos using Compiler Explorer: multiple targets with dynamic dispatch (more complicated, but flexible and uses best available SIMD) single target using -m flags (simpler, but requires/only uses the instruction set enabled by compiler flags) We have prepared several tutorial-like examples in hwy/examples; see the README.md there for more information. Basics: sum_array_advanced.cc: 4x unrolling and remainder handling. dot_product_unroll.cc: similar to sum_array_advanced, plus reduction. matrix_transpose_scatter_gather: shows/compares Scatter and Gather. Infrastructure: benchmark.cc: dot product with remainder-free loops and benchmarking. profiler_example: shows how to use the our built-in profiler for measuring the time cost of annotated zones. skeleton*: a complete example of a module with runtime dispatch. Challenges: masks_and_logic.cc: visualizes masks/comparisons with ASCII art. ctf_aes.cc: capture the flag, brute-force AES password guessing. We observe that Highway is referenced in the following open source projects, found via sourcegraph.com. Most are GitHub repositories. If you would like to add your project or link to it directly, feel free to raise an issue or contact us via the below email. Audio: Zimtohrli perceptual metric Browsers: Chromium (+Vivaldi), Firefox (+floorp / foxhound / librewolf / Waterfox) Computational biology: RNA analysis, long-sequence preprocessing Computer graphics: ghostty-org/ghostty, Sparse voxel renderer, tgfx 2D Graphics library Cryptography: google/distributed_point_functions, google/shell-encryption Data structures: bkille/BitLib Image codecs: eustas/2im, Grok JPEG 2000, JPEG XL, JPEGenc, Jpegli, libaom, OpenHTJ2K Image processing: awxkee/aire, cloudinary/ssimulacra2, libvips, m-ab-s/media-autobuild_suite, Image viewers: AlienCowEatCake/ImageViewer, diffractor/diffractor, Lux panorama/image viewer, mirillis/jpegxl-wic Information retrieval: iresearch database index, michaeljclark/zvec, nebula interactive analytics / OLAP, ScaNN Scalable Nearest Neighbors, Machine learning: array2d/deepx, gemma.cpp, Tensorflow, Numpy, zpye/SimpleInfer Programming languages: AOT-compiled python, oven-sh/bun, V8/V8, yinqiwen/rapidudf Robotics: MIT Model-Based Design and Verification Vector search: 1yefuwang1/vectorlite, vespa-engine/vespa Other Evaluation of C++ SIMD Libraries: "Highway excelled with a strong performance across multiple SIMD extensions [..]. Thus, Highway may currently be the most suitable SIMD library for many software projects." zimt: C++11 template library to process n-dimensional arrays with multi-threaded SIMD code vectorized Quicksort (paper) Highway can also be installed via a package manager or from a repository: Click to expand BSD repositories DragonFlyBSD FreeBSD GhostBSD MidnightBSD Click to expand cross platform package repositories conan-io conda-forge EasyBuild Homebrew microsoft/vcpkg spack xmake-io/xmake-repo Click to expand linux package repositories Obtained from repology Click to expand Windows package repositories fd00/yacp MSYS2 Click to expand other operating