CUDA

The pkgs.cudaPackages.backendStdenv derivation helps integrate the NVIDIA and the host compilers while making it possible to link against the CUDA libraries available in pkgs.cudaPackages.¹

Nixpkgs parametrization can affect the compatibility and availability of CUDA packages:

_module.args.pkgs = import inputs.nixpkgs {
  inherit system;
  config.allowUnfree = true;
  config.allowUnsupportedSystem = false;
  config.cudaForwardCompat = true;
  config.cudaSupport = true;
}; # _module.args.pkgs

The configuration can be done entirely with perSystem.conan options:

# file: examples/cuda-flake-parts/flake.nix
conan = {
  stdenv = pkgs.cudaPackages_13_2.backendStdenv;
  devShell = {
    tools = {
      inherit (pkgs.cudaPackages_13_2)
        cuda_nvcc
        cuda_cccl
        cuda_cudart
        cuda_nvrtc
        cuda_nvtx
        cuda_profiler_api
        cuda_cuxxfilt
        libcublas
        libnvfatbin
        libnvptxcompiler;
    };
    env = {
      LD_LIBRARY_PATH = "/usr/lib/wsl/lib";
      MESA_D3D12_DEFAULT_ADAPTER_NAME = "NVIDIA";
      GALLIUM_DRIVER = "d3d12";
    };
  };
  profiles.default = {
    settings = {
      build_type = "Release";
      "compiler.cppstd" = "20";
    };
    runEnv = [
      {
        name = "LD_LIBRARY_PATH";
        op = "+=(path)";
        value = "/usr/lib/wsl/lib";
      }
      {
        name = "MESA_D3D12_DEFAULT_ADAPTER_NAME";
        op = "=";
        value = "NVIDIA";
      }
      {
        name = "GALLIUM_DRIVER";
        op = "=";
        value = "d3d12";
      }
    ];
  };
  remotes.local = {
    url = "./repo";
    local = true;
    allowedPackages = [ "hello-world/0.0.1.cci.20260428" ];
  };
}; # conan }

The above example is on the examples/cuda-flake-parts directory:

cd examples/cuda-flake-parts
direnv allow .

And it can be validated with a call to conan create:

conan create . --build=missing

Which returns the result of the program defined in the src/modified_cuda_samples/matrixMulCUBLAS/matrixMulCUBLAS.cpp source file, on the examples/cuda-flake-parts directory:²

[Matrix Multiply CUBLAS] - Starting...
Using CUDA device NVIDIA GeForce RTX 3060 Laptop GPU (having device ID 0)
GPU Device 0: "NVIDIA GeForce RTX 3060 Laptop GPU" with compute capability 8.6
MatrixA(640,480), MatrixB(480,320), MatrixC(640,320)
Computing result using CUBLAS... done.
Performance= 4266.67 GFlop/s, Time= 0.046 msec, Size= 196608000 Ops
Computing result using host CPU... done.
CUBLAS Matrix Multiply is close enough to CPU results: Yes
SUCCESS

1. See CUDA Modules for an overview on how CUDA packages are structured in Nixpkgs. ↩

2. The source files src/modified_cuda_samples/matrixMulCUBLAS/matrixMulCUBLAS.cpp and src/common.hpp are taken from the examples of the cuda-api-wrappers project — examples/modified_cuda_samples/matrixMulCUBLAS/matrixMulCUBLAS.cpp and examples/common.hpp, respectively. ↩