# Halide **Repository Path**: mirrors_trending/Halide ## Basic Information - **Project Name**: Halide - **Description**: a language for fast, portable data-parallel computation - **Primary Language**: C++ - **License**: Apache-2.0 - **Default Branch**: main - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 1 - **Forks**: 0 - **Created**: 2020-08-13 - **Last Updated**: 2026-03-14 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README # Halide Halide is a programming language designed to make it easier to write high-performance image and array processing code on modern machines. Halide currently targets: - CPU architectures: X86, ARM, Hexagon, PowerPC, RISC-V, WebAssembly - Operating systems: Linux, Windows, macOS, Android, iOS, Qualcomm QuRT - GPU Compute APIs: CUDA, OpenCL, Apple Metal, Microsoft Direct X 12, Vulkan Rather than being a standalone programming language, Halide is embedded in C++. This means you write C++ code that builds an in-memory representation of a Halide pipeline using Halide's C++ API. You can then compile this representation to an object file, or JIT-compile it and run it in the same process. Halide also provides a Python binding that provides full support for writing Halide embedded in Python without C++. Halide requires C++17 (or later) to use. For more detail about what Halide is, see https://halide-lang.org. For API documentation see https://halide-lang.org/docs. For some example code, read through the tutorials online at https://halide-lang.org/tutorials. The corresponding code is in the `tutorials/` directory. Larger examples are in the `apps/` directory. If you've acquired a full source distribution and want to build Halide, see the [notes below](#building-halide). # Getting Halide ## Pip We provide binary wheels on PyPI. Halide provides bindings for C++ and Python. Even if you only intend to use Halide from C++, pip may be the easiest way to get a binary build of Halide. Full releases may be installed with `pip` like so: ```shell $ pip install halide ``` Every commit to `main` is published to our [package index][halide-pypi] as a development version. If you use [uv](https://docs.astral.sh/uv/), you can pin the nightly Halide in a project like so: ```shell $ uv add halide --prerelease=allow --index https://pypi.halide-lang.org/simple ``` Or install directly with `pip`: ```shell $ pip install halide --pre --extra-index-url https://pypi.halide-lang.org/simple ``` Currently, we provide wheels for: Windows x86-64, macOS x86-64, macOS arm64, and Linux x86-64. The Linux wheels are built for manylinux_2_28, which makes them broadly compatible (Debian 10, Ubuntu 18.10, Fedora 29). *For C++ usage of the pip package:* On Linux and macOS, CMake's `find_package` command should find Halide as long as you're in the same virtual environment you installed it in. On Windows, you will need to add the virtual environment root directory to `CMAKE_PREFIX_PATH`. This can be done by running `set CMAKE_PREFIX_PATH=%VIRTUAL_ENV%` in `cmd`. Other build systems can find the Halide root path by running `python -c "import halide; print(halide.install_dir())"`. [halide-pypi]: https://pypi.halide-lang.org/simple ## Homebrew Alternatively, if you use macOS, you can install Halide via [Homebrew](https://brew.sh/) like so: ``` $ brew install halide ``` ## Binary tarballs The latest version of Halide can always be found on GitHub at https://github.com/halide/Halide/releases We provide binary releases for many popular platforms and architectures, including 32/64-bit x86 Windows, 64-bit x86/ARM macOS, and 32/64-bit x86/ARM Ubuntu Linux. The Linux tarballs are built on a recent Ubuntu LTS; if your distribution is too old, it might not have the requisite glibc. The [pip wheels](#pip) are built for manylinux_2_28 and are more broadly compatible. ## Vcpkg If you use [vcpkg](https://github.com/microsoft/vcpkg) to manage dependencies, you can install Halide via: ``` $ vcpkg install halide:x64-windows # or x64-linux/x64-osx ``` One caveat: vcpkg installs only the minimum Halide backends required to compile code for the active platform. If you want to include all the backends, you should install `halide[target-all]:x64-windows` instead. ## Other package managers We are interested in bringing Halide to other popular package managers and Linux distribution repositories! We track the status of various distributions of Halide [in this GitHub issue](https://github.com/halide/Halide/issues/4660). If you have experience publishing packages we would be happy to work with you! # Building Halide ## Platform Support There are two sets of platform requirements relevant to Halide: those required to run the compiler library in either JIT or AOT mode, and those required to run the _binary outputs_ of the AOT compiler. These are the **tested** host toolchain and platform combinations for building and running the Halide compiler library. | Compiler | Version | OS | Architectures | |------------|--------------|------------------------|---------------| | GCC | 9.5 | Ubuntu Linux 20.04 LTS | x86, x64 | | GCC | 11.4 | Ubuntu Linux 22.04 LTS | ARM32, ARM64 | | MSVC | 2022 (19.37) | Windows 11 (22631) | x86, x64 | | AppleClang | 15.0.0 | macOS 14.4.1 | x64 | | AppleClang | 14.0.0 | macOS 14.6 | ARM64 | Some users have successfully built Halide for Linux using Clang 9.0.0+, for Windows using ClangCL 11.0.0+, and for Windows ARM64 by cross-compiling with MSVC. We do not actively test these scenarios, however, so your mileage may vary. Beyond these, we are willing to support (by accepting PRs for) platform and toolchain combinations that still receive _active, first-party, public support_ from their original vendors. For instance, at time of writing, this excludes Windows 7 and includes Ubuntu 18.04 LTS. Compiled AOT pipelines are expected to have much broader platform support. The binaries use the C ABI, and we expect any compliant C compiler to be able to use the generated headers correctly. The C++ bindings currently require C++17. If you discover a compatibility problem with a generated pipeline, please open an issue. ## Acquiring LLVM At any point in time, building Halide requires either the latest stable version of LLVM, the previous stable version of LLVM, or trunk. At the time of writing, this means versions 23, 22, and 21 are supported, but 20 is not. We publish the LLVM builds we use in CI as Python packages on our [package index][halide-pypi]. This is the easiest way to get a suitable LLVM on any platform. From the Halide source tree, install with [uv](https://docs.astral.sh/uv/): ```shell $ uv sync --group ci-llvm-22 --no-install-project $ export Halide_LLVM_ROOT=$(halide-llvm --prefix) ``` Replace `22` with the desired LLVM major version (`21`, `22`, `23`, or `main`). Binary wheels are available for Linux (x86-64, x86-32, AArch64, ARMv7), macOS (x86-64, ARM64), and Windows (x86-64, x86-32). On macOS, [Homebrew](https://brew.sh) is also a good option: `brew install llvm`. On Debian flavors of Linux, the [LLVM APT repo](https://apt.llvm.org) works well; use the provided installation script.
Building LLVM from source (advanced) > [!WARNING] > Building LLVM from source requires significant time, disk space, and RAM. > Prefer the pre-built binaries above unless you need a custom configuration. First check it out from GitHub: ```shell $ git clone --depth 1 --branch llvmorg-21.1.8 https://github.com/llvm/llvm-project.git ``` (LLVM 21.1.8 is the most recent released LLVM at the time of writing. For current trunk, use `main` instead) Then build it like so: ```shell $ cmake -G Ninja -S llvm-project/llvm -B build \ -DCMAKE_BUILD_TYPE=Release \ -DLLVM_ENABLE_PROJECTS="clang;lld;clang-tools-extra" \ -DLLVM_ENABLE_RUNTIMES=compiler-rt \ -DLLVM_TARGETS_TO_BUILD="WebAssembly;X86;AArch64;ARM;Hexagon;NVPTX;PowerPC;RISCV" \ -DLLVM_ENABLE_ASSERTIONS=ON \ -DLLVM_ENABLE_EH=ON \ -DLLVM_ENABLE_RTTI=ON \ -DLLVM_ENABLE_HTTPLIB=OFF \ -DLLVM_ENABLE_LIBEDIT=OFF \ -DLLVM_ENABLE_LIBXML2=OFF \ -DLLVM_ENABLE_TERMINFO=OFF \ -DLLVM_ENABLE_ZLIB=OFF \ -DLLVM_ENABLE_ZSTD=OFF \ -DLLVM_BUILD_32_BITS=OFF $ cmake --build build $ cmake --install build --prefix llvm-install ``` This will produce a working LLVM installation in `$PWD/llvm-install`. We refer to this path as `LLVM_ROOT` later. **Do not confuse this installation tree with the build tree!** LLVM takes a long time to build, so the above command uses Ninja to maximize parallelism. If you choose to omit `-G Ninja`, Makefiles will be generated instead. In this case, enable parallelism with `cmake --build build -j NNN` where `NNN` is the number of parallel jobs, i.e. the number of CPUs you have. Note that you _must_ add `clang` and `lld` to `LLVM_ENABLE_PROJECTS` and `WebAssembly` and `X86` _must_ be included in `LLVM_TARGETS_TO_BUILD`. `LLVM_ENABLE_RUNTIMES=compiler-rt` is only required to build the fuzz tests, and `clang-tools-extra` is only necessary if you plan to contribute code to Halide (so that you can run `clang-tidy` on your pull requests). You can disable exception handling (EH) and RTTI if you don't want the Python bindings. We recommend enabling the full set to simplify builds during development.
## Building Halide with CMake This is discussed in greater detail in [BuildingHalideWithCMake.md]. CMake version 3.28+ is required to build Halide. [BuildingHalideWithCMake.md]: doc/BuildingHalideWithCMake.md ### MacOS and Linux After [acquiring LLVM](#acquiring-llvm), change directory to the Halide repository and run: ```shell $ cmake -G Ninja -S . -B build -DCMAKE_BUILD_TYPE=Release -DHalide_LLVM_ROOT=$LLVM_ROOT $ cmake --build build ``` Setting `-DHalide_LLVM_ROOT` is not required if you have a suitable system-wide version installed. However, if you have multiple LLVMs installed, it can pick between them. Do not use a relative path for `Halide_LLVM_ROOT`. It can cause problems on some systems. If you use [Homebrew](https://brew.sh/) on macOS, you can use the provided CMake preset: ```shell $ cmake --preset=macOS -S . -B build $ cmake --build build ``` This automatically finds LLVM from Homebrew's install path. ### Windows We suggest building with Visual Studio 2022. Your mileage may vary with earlier versions. Be sure to install the "C++ CMake tools for Windows" in the Visual Studio installer. For older versions of Visual Studio, do not install the CMake tools, but instead acquire CMake and Ninja from their respective project websites. These instructions start from the `D:` drive. We assume this git repo is cloned to `D:\Halide`. We also assume that your shell environment is set up correctly. For a 64-bit build, run: ``` D:\> "C:\Program Files (x86)\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsall.bat" x64 ``` For a 32-bit build, run: ``` D:\> "C:\Program Files (x86)\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsall.bat" x64_x86 ``` #### Managing dependencies with vcpkg The best way to get compatible dependencies on Windows is to use [vcpkg](https://github.com/Microsoft/vcpkg). Install it like so: ``` D:\> git clone https://github.com/Microsoft/vcpkg.git D:\> cd vcpkg D:\vcpkg> .\bootstrap-vcpkg.bat -disableMetrics ... CMake projects should use: "-DCMAKE_TOOLCHAIN_FILE=D:/vcpkg/scripts/buildsystems/vcpkg.cmake" ``` Halide includes a `vcpkg-configuration.json` that automatically configures [overlay ports](https://learn.microsoft.com/en-us/vcpkg/concepts/overlay-ports) and overlay triplets. These overlays redirect LLVM and Python to system installations, so vcpkg only builds the smaller dependencies (flatbuffers, wabt, pybind11, etc.). You must have LLVM and Python installed separately (see [Acquiring LLVM](#acquiring-llvm) above). #### Building Halide Create a separate build tree and call CMake with vcpkg's toolchain. This will build in either 32-bit or 64-bit depending on the environment script (`vcvars`) that was run earlier. ``` D:\Halide> cmake -G Ninja -S . -B build ^ --toolchain D:/vcpkg/scripts/buildsystems/vcpkg.cmake ^ -DCMAKE_BUILD_TYPE=Release ``` Or use a CMake preset (e.g. for a Visual Studio build): ``` D:\Halide> cmake --preset=win64 &:: or win32 for 32-bit D:\Halide> cmake --build build\win64 ``` For a Ninja-based build with vcpkg: ``` D:\Halide> cmake --preset=release-vcpkg -S . -B build D:\Halide> cmake --build build ``` To run all the tests: ``` D:\Halide> ctest --test-dir build --output-on-failure ``` Subsets of the tests can be selected with `-L` and include `correctness`, `generator`, `error`, and the other directory names under `tests/`.
Building LLVM from source on Windows (advanced) > [!WARNING] > Building LLVM from source requires significant time, disk space, and RAM. > Prefer the pre-built `halide-llvm` binaries (see > [Acquiring LLVM](#acquiring-llvm)) unless you need a custom configuration. First, download LLVM's sources (these instructions use the 21.1.8 release). ``` D:\> git clone --depth 1 --branch llvmorg-21.1.8 https://github.com/llvm/llvm-project.git ``` As above, run `vcvarsall.bat` to pick between x86 and x64. Then configure LLVM with the following command (for 32-bit, set `-DLLVM_BUILD_32_BITS=ON` instead): ``` D:\> cmake -G Ninja -S llvm-project\llvm -B build ^ -DCMAKE_BUILD_TYPE=Release ^ -DLLVM_ENABLE_PROJECTS=clang;lld;clang-tools-extra ^ -DLLVM_ENABLE_RUNTIMES=compiler-rt ^ -DLLVM_TARGETS_TO_BUILD=WebAssembly;X86;AArch64;ARM;Hexagon;NVPTX;PowerPC;RISCV ^ -DLLVM_ENABLE_ASSERTIONS=ON ^ -DLLVM_ENABLE_EH=ON ^ -DLLVM_ENABLE_RTTI=ON ^ -DLLVM_ENABLE_HTTPLIB=OFF ^ -DLLVM_ENABLE_LIBEDIT=OFF ^ -DLLVM_ENABLE_LIBXML2=OFF ^ -DLLVM_ENABLE_TERMINFO=OFF ^ -DLLVM_ENABLE_ZLIB=OFF ^ -DLLVM_ENABLE_ZSTD=OFF ^ -DLLVM_BUILD_32_BITS=OFF ``` **MSBuild:** If you want to build LLVM with MSBuild instead of Ninja, use `-G "Visual Studio 17 2022" -Thost=x64 -A x64` or `-G "Visual Studio 17 2022" -Thost=x64 -A Win32` in place of `-G Ninja`. Finally, run the build and install to a local directory: ``` D:\> cmake --build build --config Release D:\> cmake --install build --prefix llvm-install ``` You can substitute `Debug` for `Release` in the above `cmake` commands if you want a debug build. To use this with Halide, but still allow vcpkg to manage other dependencies, point CMake to your LLVM with `-DHalide_LLVM_ROOT=D:/llvm-install`. The overlay ports in `vcpkg-configuration.json` automatically prevent vcpkg from trying to build its own LLVM.
#### If all else fails... Do what the buildbots do: https://buildbot.halide-lang.org/master/#/builders If the row that best matches your system is red, then maybe things aren't just broken for you. If it's green, then you can click through to the latest build and see the commands that the build bots run. Open a step ("Configure Halide" is useful) and look at the "stdio" logs in the viewer. These logs contain the full commands that were run, as well as the environment variables they were run with. ## Building Halide with make > [!WARNING] > We do not provide support for the Makefile. Feel free to use it, but if > anything goes wrong, switch to the CMake build. Note also that the Makefile > cannot build the Python bindings or produce install packages. *TL;DR*: Have LLVM 17 (or greater) installed and run `make` in the root directory of the repository (where this README is). By default, `make` will use the `llvm-config` tool found in the `PATH`. If you want to use a different LLVM, such as a custom-built one following the instructions above, set the following environment variable: ```shell $ export LLVM_CONFIG="$LLVM_ROOT/bin/llvm-config" ``` Now you should be able to just run `make` in the root directory of the Halide source tree. `make run_tests` will run the JIT test suite, and `make test_apps` will make sure all the apps compile and run (but won't check their output). When building the tests, you can set the AOT compilation target with the `HL_TARGET` environment variable. ### Building Halide out-of-tree with make If you wish to build Halide in a separate directory, you can do that like so: ```shell $ cd .. $ mkdir halide_build $ cd halide_build $ make -f ../Halide/Makefile ``` # Some useful environment variables `HL_JIT_TARGET=...` will set Halide's JIT compilation target. `HL_DEBUG_CODEGEN=1` will print out pseudocode for what Halide is compiling. Higher numbers will print more detail. `HL_NUM_THREADS=...` specifies the number of threads to create for the thread pool. When the async scheduling directive is used, more threads than this number may be required and thus allocated. A maximum of 256 threads is allowed. (By default, the number of cores on the host is used.) `HL_TRACE_FILE=...` specifies a binary target file to dump tracing data into (ignored unless at least one `trace_` feature is enabled in the target). The output can be parsed programmatically by starting from the code in `utils/HalideTraceViz.cpp`. # Further references We have more documentation in `doc/`, the following links might be helpful: | Document | Description | |-----------------------------------------------|---------------------------------------------------------------------------| | [CMake build](doc/BuildingHalideWithCMake.md) | How to configure and build Halide using CMake. | | [CMake package](doc/HalideCMakePackage.md) | How to use the Halide CMake package to build your code. | | [Hexagon](doc/Hexagon.md) | How to use the Hexagon backend. | | [Python](doc/Python.md) | Documentation for the Python bindings. | | [RunGen](doc/RunGen.md) | How to use the RunGen interface to run and benchmark arbitrary pipelines. | | [Vulkan](doc/Vulkan.md) | How to use the Halide Vulkan backend (BETA) | | [WebAssembly](doc/WebAssembly.md) | How to use the WebAssembly backend and how to use V8 in place of wabt. | | [WebGPU](doc/WebGPU.md) | How to run WebGPU pipelines (BETA) | The following links are of greater interest to developers wishing to contribute code to Halide: | Document | Description | |------------------------------------------|---------------------------------------------------------------------------------------------------------------| | [CMake developer](doc/CodeStyleCMake.md) | Guidelines for authoring new CMake code. | | [FuzzTesting](doc/FuzzTesting.md) | Information about fuzz testing the Halide compiler (rather than pipelines). Intended for internal developers. | | [Testing](doc/Testing.md) | Information about our test organization and debugging tips. Intended for internal developers. |