Maybe you missed the part where the program tells the user it's running in "CPU Mode" and may be slower, "Try running on a GPU" is another message that would make it clear.

So many comments here make it seem like we're dealing with people with a negative IQ.

Just show an appropriate message and let the user run the software. It's GREAT that there is a simple CPU fallback and it's enabled by default.

It's really an edge-case where a user would want to run the code and have it fail if there isn't a GPU - that is mostly an edge case of 1 user, the developer, except in very specialized situations where nobody would want to run it without a GPU, again an edge-case.