How to convert a cupy.ndarray to a scalar?

I'm working with CuPy at the moment. I've noticed something that seems to be a bug, but I'm not sure.

I've noticed that if I use certain math functions, they result in the wrong shape. For example:

if I do this using numpy it returns a scalar with no shape. As it should.

s8 = numpy.abs(2)

However if I use CuPy:

s8 = cupy.abs(2)

It results in cupy.ndarray. When evaluated with s8.shape, it returns ()

The frustrating part is trying to convert cupy.ndarray into a scalar with no shape. I've tried using: cupy.Squeeze(s8) and s8.item() to return just the scalar. In both cases it returns the value but retains the shape. I've also tried using float(s8) and int(s8). Both of which return the appropriate value type, but the array still remains.

Any thoughts on how to convert this from a cupy.ndarray to a scalar?

Solution

This is a known behavior in CuPy and is not a bug: https://docs.cupy.dev/en/stable/reference/difference.html#reduction-methods

Unlike in NumPy (which makes the distinction between scalars and 0-d arrays), all scalars in CuPy are 0-d arrays, otherwise it would unavoidably lead to a data transfer by converting them to Python scalars, which compromises the performance.