You can try this:
You can change the default GPU for a program through the NVIDIA Control Panel, simply Right-Click on the Lightroom Icon and select Run with Graphics processor -> Choose Default Graphics processor ...
Then you will be given an option to select the preferred graphics processor for Lightroom.
from thread https://forums.adobe.com/message/7506598#7506598
Daniel (from Switzerland)
thanks for your answer.
I tried to use the nvidia control panel but in the 3D parameters panel Lightroom doesn't appear in the programs list. So I added the lightroom program and change the parameter to "high performance process".
After that when I load lightroom the used graphic card is still the intel one.
When i came back in the nvidia control panel, lightroom does'nt appear anymore in the 3D parameters and its look like I have never configured it...
It is strange, maybe I'm going to contact nvidia
In fact if I right clic on the lightroom.exe and choose "Run we graphic processor/ High performance" it is working.
But it's pretty ennoying to do this each time that I want to use Lightroom!