Convert CuPy array to PyCUDA array

test_cupy_to_pycuda.py

import cupy as cp
from pycuda import gpuarray
import pycuda.autoinit  # this import creates a CUDA context!


def from_cupy(arr):
    shape = arr.shape
    dtype = arr.dtype

    # a dummy object always returns the underlying pointer address
    def alloc(x):
        return arr.data.ptr

    if arr.flags.c_contiguous:
        order = 'C'
    elif arr.flags.f_contiguous:
        order = 'F'
    else:
        raise ValueError('arr order cannot be determined')
    return gpuarray.GPUArray(shape=shape,
                             dtype=dtype,
                             allocator=alloc,
                             order=order)

a = cp.arange(10)
x = from_cupy(a)
x+=3
print(a)  # output: [ 3  4  5  6  7  8  9 10 11 12]

For the record, this is to help a friend transition from PyCUDA to CuPy, which is an advise that I give everywhere as a CuPy core contributor.