The CPU implementation had the following downsides:
- The kernels sizes below 3 did not make much sense, often leading
to a full white image.
- The way how the total number of pixels in the kernel was calculated
quite strangely.
From these points of view the GPU compositor behaves more user friendly.
There is a versioning code which lowers the kernel size, to match the
result prior to these tweaks.
Pull Request: https://projects.blender.org/blender/blender/pulls/117505
ca767644eb