Hi @rd52 and @Marco.Djallo, that last line of the log is misleading, you can ignore that, check out this place:
All the log is saying that OpenCL is available on your machine, and it has successfully compiled the OpenCL kernels, so in theory it should work.
You can find more information on dt and OpenCL here:
if you experience performance problems, I’d suggest to start darktable (not the cltest utility) itself with the following command line parameters (pls enable OpenCL before):
darktable -d opencl -d perf
And try to edit the picture with the module which you have problem with. After that please share the output of the log, which you can find here: