Installing PyOpenCL on Mac OS Catalina

python-env-mac-with-pyopencl.nix

let

  pkgs = import (builtins.fetchTarball {
    url =
      "https://github.com/NixOS/nixpkgs-channels/archive/nixpkgs-20.03-darwin.tar.gz";
    sha256 = "0wci9vylb31wvl3zslw38537dgdvd89w58fvj9acnbv9l378x3hh";
  }) { };

  packageOverrides = self: super: {
    pyopencl = super.pyopencl.overridePythonAttrs (old: rec {
      buildInputs = with pkgs; [ opencl-headers pybind11 libGL_driver.dev ];
    });
  };

  python = pkgs.python3.override {
    inherit packageOverrides;
  };

  # `setuptools` is required to solve the missing `pkg_resources` module not
  # found error. See https://nixos.wiki/wiki/Packaging/Python
  pythonEnv =
    python.withPackages (ps: with ps; [ numpy ipython pyopencl setuptools ]);

in pythonEnv.env

test.py

#!/usr/bin/env python
# Copied from the pyopencl website with minor modifications
import numpy as np
import pyopencl as cl

a_np = np.random.rand(500).astype(np.float32) # Modified from original 50000 elements to 500
b_np = np.random.rand(500).astype(np.float32) # Modified from original 50000 elements to 500

ctx = cl.create_some_context()
queue = cl.CommandQueue(ctx)

mf = cl.mem_flags
a_g = cl.Buffer(ctx, mf.READ_ONLY | mf.COPY_HOST_PTR, hostbuf=a_np)
b_g = cl.Buffer(ctx, mf.READ_ONLY | mf.COPY_HOST_PTR, hostbuf=b_np)

prg = cl.Program(ctx, """
__kernel void sum(
    __global const float *a_g, __global const float *b_g, __global float *res_g)
{
  int gid = get_global_id(0);
  res_g[gid] = a_g[gid] + b_g[gid];
}
""").build()

res_g = cl.Buffer(ctx, mf.WRITE_ONLY, a_np.nbytes)
prg.sum(queue, a_np.shape, None, a_g, b_g, res_g)

res_np = np.empty_like(a_np)
cl.enqueue_copy(queue, res_np, res_g)

# Check on CPU with Numpy:
print(res_np - (a_np + b_np))
print(np.linalg.norm(res_np - (a_np + b_np)))
assert np.allclose(res_np, a_np + b_np)

Note that setuptools is needed when running in an environment in order to solve the error

ModuleNotFoundError: No module named 'pkg_resources'