Quickstart

Installation

Install cunumpy directly from PyPI:

pip install cunumpy

Basic Usage

Replace import numpy as np with import cunumpy as xp. By default, it will use NumPy if CuPy is not installed or configured.

import cunumpy as xp

# Create an array (automatically uses the active backend)
arr = xp.array([1, 2, 3])

print(f"Array type: {type(arr)}")
print(f"Active backend: {xp.get_backend(arr)}")

Backend Control

You can control the backend using environment variables:

export ARRAY_BACKEND=cupy

Or programmatically:

import cunumpy as xp

# Globally set backend
xp.set_backend("cupy")

# Scoped backend switching
with xp.use_backend("numpy"):
    arr_cpu = xp.zeros(10)
    print(xp.is_cpu(arr_cpu))  # True

# Explicit conversion
arr_np = xp.to_numpy(arr)
arr_cp = xp.to_cupy(arr)

Synchronization

When using the GPU, it’s important to synchronize for accurate timing:

import time
import cunumpy as xp

xp.set_backend("cupy")
a = xp.random.rand(1000, 1000)

start = time.time()
b = xp.dot(a, a)
xp.synchronize()  # Wait for GPU
end = time.time()

print(f"Elapsed: {end - start:.4f}s")