Using MLX in C++

You can use MLX in a C++ project with CMake.

Note

This guide is based one the following example using MLX in C++

First install MLX:

pip install -U mlx

You can also install the MLX Python package from source or just the C++ library. For more information see the documentation on installing MLX.

Next make an example program in example.cpp:

#include <iostream>

#include "mlx/mlx.h"

namespace mx = mlx::core;

int main() {
  auto x = mx::array({1, 2, 3});
  auto y = mx::array({1, 2, 3});
  std::cout << x + y << std::endl;
  return 0;
}

The next step is to setup a CMake file in CMakeLists.txt:

cmake_minimum_required(VERSION 3.27)

project(example LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

Depending on how you installed MLX, you may need to tell CMake where to find it.

If you installed MLX with Python, then add the following to the CMake file:

find_package(
  Python 3.9
  COMPONENTS Interpreter Development.Module
  REQUIRED)
execute_process(
  COMMAND "${Python_EXECUTABLE}" -m mlx --cmake-dir
  OUTPUT_STRIP_TRAILING_WHITESPACE
  OUTPUT_VARIABLE MLX_ROOT)

If you installed the MLX C++ package to a system path, then CMake should be able to find it. If you installed it to a non-standard location or CMake can’t find MLX then set MLX_ROOT to the location where MLX is installed:

set(MLX_ROOT "/path/to/mlx/")

Next, instruct CMake to find MLX:

find_package(MLX CONFIG REQUIRED)

Finally, add the example.cpp program as an executable and link MLX.

add_executable(example example.cpp)
target_link_libraries(example PRIVATE mlx)

You can build the example with:

cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build

And run it with:

./build/example

Note find_package(MLX CONFIG REQUIRED) sets the following variables:

Package Variables

Variable	Description
MLX_FOUND	True if MLX is found
MLX_INCLUDE_DIRS	Include directory
MLX_LIBRARIES	Libraries to link against
MLX_CXX_FLAGS	Additional compiler flags
MLX_BUILD_ACCELERATE	True if MLX was built with Accelerate
MLX_BUILD_METAL	True if MLX was built with Metal