CuNumpy

Simple wrapper for numpy and cupy. Replace import numpy as np with import cunumpy as xp.

Install

pip install cunumpy

Example usage:

export ARRAY_BACKEND=cupy

import cunumpy as xp

xp.set_backend("cupy")

arr = xp.array([1, 2])

print(f"{type(arr) = }")
print(f"{xp.__version__ = }")

# Convert to NumPy
arr_np = xp.to_numpy(arr)

# Convert to active backend
arr_xp = xp.to_cunumpy(arr)

# Inspect backend
print(f"{xp.get_backend(arr) = }")
print(f"{xp.is_gpu(arr) = }")
print(f"{xp.is_cpu(arr) = }")

# Temporarily switch backend
with xp.use_backend("numpy"):
    # This code runs on CPU even if ARRAY_BACKEND=cupy
    arr_cpu = xp.zeros(100)

# Set backend globally
xp.set_backend("cupy")

# Synchronize GPU operations (no-op on CPU)
xp.synchronize()

Output:

type(arr) = <class 'cupy.ndarray'>
xp.__version__ = '0.1.4'
xp.get_backend(arr) = 'cupy'
xp.is_gpu(arr) = True
xp.is_cpu(arr) = False

Pyodide

cuNumPy supports Pyodide with the NumPy backend. In an initialized Pyodide JavaScript runtime, install the package and run a Python-source kernel:

await pyodide.loadPackage("micropip");
await pyodide.runPythonAsync(`
    import micropip
    await micropip.install("cunumpy")

    import cunumpy as xp
    xp.set_backend("numpy")

    def scale(values, factor):
        values[:] *= factor
        return values

    values = xp.array([1.0, 2.0, 3.0])
    result = xp.PyccelKernel(scale)(values, 2.0)
    assert result is values
    print(xp.to_numpy(result))  # [2. 4. 6.]
`);

NumPy is the default backend when ARRAY_BACKEND is unset. CuPy/CUDA and native Pyccel compilation are not supported in Pyodide. Despite its name, PyccelKernel accepts ordinary Python callables and neither imports Pyccel nor compiles code. Applications must supply Python-source kernels with Pyodide-compatible imports.

CI tests the built wheel in Pyodide's WebAssembly runtime under Node.js, including array operations, conversions, mutation/aliasing, backend context restoration, and Python kernels, while rejecting CuPy or Pyccel imports. This does not test browser-specific integration such as page loading or workers. See the Pyodide guide for details and local test commands.

Development tests

pip install -e '.[test]'
pytest tests/portable

The test extra is compiler-free. For compiled-kernel tests, install '.[test-compiled]' and a working native compiler, then run pytest. The dev extra includes these compiled-test dependencies as before.

Build docs

make html
cd ../
open docs/_build/html/index.html