Hi ptrblck,
Thanks for your answer, I was actually hoping for an answer from you :-).
Now I understand why what I have tried does not work.
I’ve had a look at the post your have gently shared, would Model parallel solve the issue?
If I understand well, I have to spilt my input data (image) In two/four, send the splitter data to the different gpus and merge the data after process completion is that correct?
Could you show me how you would use Model parallel  in this precise case? My input image is a jpg image.
Thanks a lot