What’s happening on your system is really strange. I have a similar situation, i.e. laptop with both integrated intel graphics and external nvidia card (it’s a Dell XPS 15 9560 i7-7700HQ@2.8Ghz Kabylake, the internal gpu is an Intel HD630 and then there’s the Geforce GTX1050).
But there’s no way I can use OpenCL if I’m using the prime profile Intel!
This is now, Intel GPU active, look at the result of darktable-cltest:
$ darktable-cltest
0.086798 [opencl_init] opencl related configuration options:
0.086834 [opencl_init]
0.086845 [opencl_init] opencl: 1
0.086859 [opencl_init] opencl_library: ''
0.086875 [opencl_init] opencl_memory_requirement: 768
0.086905 [opencl_init] opencl_memory_headroom: 300
0.086919 [opencl_init] opencl_device_priority: '*/!0,*/*/*'
0.086934 [opencl_init] opencl_mandatory_timeout: 200
0.086947 [opencl_init] opencl_size_roundup: 16
0.086960 [opencl_init] opencl_async_pixelpipe: 0
0.086973 [opencl_init] opencl_synch_cache: 0
0.086989 [opencl_init] opencl_number_event_handles: 25
0.087003 [opencl_init] opencl_micro_nap: 1000
0.087015 [opencl_init] opencl_use_pinned_memory: 0
0.087027 [opencl_init] opencl_use_cpu_devices: 0
0.087039 [opencl_init] opencl_avoid_atomics: 0
0.087050 [opencl_init]
0.087477 [opencl_init] could not find opencl runtime library 'libOpenCL'
0.087643 [opencl_init] could not find opencl runtime library 'libOpenCL.so'
0.088052 [opencl_init] found opencl runtime library 'libOpenCL.so.1'
0.088120 [opencl_init] opencl library 'libOpenCL.so.1' found on your system and loaded
0.094027 [opencl_init] could not get platforms: -1001
0.094052 [opencl_init] FINALLY: opencl is NOT AVAILABLE on this system.
0.094060 [opencl_init] initial status of opencl enabled flag is OFF.
Now, it would be really great if I could be running Intel GPU all the time (laptop is less hungry, less noisy, etc) and then still launch Darktable with openCL support whenever I’m working on photos.
About the gpu not being recognized after waking up from sleep, try this:
$ sudo rmmod nvidia_uvm; sudo modprobe nvidia_uvm'
I have the above command set as an alias: alias startgpu='sudo rmmod nvidia_uvm; sudo modprobe nvidia_uvm'
For another discussion on darktable and opencl (and the settings to use), check this discussion: https://discuss.pixls.us/t/darktable-core-options-for-i7-16gb-ram-etc/10354