On 16.04, OpenCL worked with my Nvidia 840M running the latest Nvidia drivers in the Ubuntu repos.
I've done a fresh install for 18.04, however using the 390 Nvidia drivers from the Ubuntu repos (not from any PPA). Now none of my OpenCL compatible applications are able to use it.
Am I wrong that OpenCL should just work once the Nvidia drivers are installed?
nvidia-390
without problems. I have used it and it worked fine. The only thing that my answer is actually pointing out is that the driver name has changed from Ubuntu 16.04 and thegraphics-drivers
ppa to Ubuntu 18.04 where it is nownvidia-driver-39x
where396.24
is the newest driver. Seems fairly stable. As far as CUDA goes I would suggest reading through the Wiki page on it for what it can give you: https://en.wikipedia.org/wiki/CUDA – Terrance May 05 '18 at 21:39